Xylitol Production

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Inês Conceição Roberto - One of the best experts on this subject based on the ideXlab platform.

  • the behavior of key enzymes of xylose metabolism on the Xylitol Production by candida guilliermondii grown in hemicellulosic hydrolysate
    Journal of Industrial Microbiology & Biotechnology, 2009
    Co-Authors: Daniela De Borba Gurpilhares, Adalberto Pessoa, Francislene Andreia Hasmann, Inês Conceição Roberto
    Abstract:

    A variety of raw materials have been used in fermentation process. This study shows the use of rice straw hemicellulosic hydrolysate, as the only source of nutrient, to produce high added-value products. In the present work, the activity of the enzymes xylose reductase (XR); Xylitol dehydrogenase (XD); and glucose-6-phosphate dehydrogenase (G6PD) during cultivation of Candida guilliermondii on rice straw hemicellulosic hydrolysate was measured and correlated with Xylitol Production under different pH values (around 4.5 and 7.5) and initial xylose concentration (around 30 and 70 g l−1). Independent of the pH value and xylose concentration evaluated, the title of XD remained constant. On the other hand, the volumetric activity of G6PD increased whereas the level of XR decreased when the initial xylose concentration was increased from 30 to 70 g l−1. The highest values of Xylitol productivity (Q P ≈ 0.40 g l−1) and yield factor (Y P/S ≈ 0.60 g g−1) were reached at highest G6PD/XR ratio and lowest XR/XD ratio. These results suggest that NADPH concentrations influence the formation of Xylitol more than the activity ratios of the enzymes XR and XD. Thus, an optimal rate between G6PD and XR must be reached in order to optimize the Xylitol Production.

  • optimal experimental condition for hemicellulosic hydrolyzate treatment with activated charcoal for Xylitol Production
    Biotechnology Progress, 2008
    Co-Authors: Solange I. Mussatto, Inês Conceição Roberto
    Abstract:

    Rice straw was hydrolyzed into a mixture of sugars using diluted H2SO4. During hydrolysis, a variety of inhibitors was also produced, including acetic acid, furfural, hydroxymethylfurfural, and lignin degradation products (several aromatic and phenolic compounds). To reduce the toxic compounds concentration in the hydrolyzate and to improve the Xylitol yield and volumetric productivity, rice straw hemicellulosic hydrolyzate was treated with activated charcoal under different pH values, stirring rates, contact times, and temperatures, employing a 24 full-factorial design. Fermentative assays were conducted with treated hydrolyzates containing 90 g/L xylose. The results indicated that temperature, pH, and stirring rate strongly influenced the hydrolyzate treatment, temperature and pH interfering with all of the responses analyzed (removal of color and lignin degradation products, Xylitol yield factor, and volumetric productivity). The combination of pH 2.0, 150 rpm, 45 °C, and 60 min was considered an optimal condition, providing significant removal rates of color (48.9%) and lignin degradation products (25.8%), as well as a Xylitol Production of 66 g/L, a volumetric productivity of 0.57 g/L·h, and a yield factor of 0.72 g/g.

  • kinetic behavior of candida guilliermondii yeast during Xylitol Production from brewerapos s spent grain hemicellulosic hydrolysate
    Biotechnology Progress, 2008
    Co-Authors: Solange I. Mussatto, Giuliano Dragone, Inês Conceição Roberto
    Abstract:

    Brewerapos;s spent grain, the main byproduct of breweries, was hydrolyzed with dilute sulfuric acid to produce a hemicellulosic hydrolysate (containing xylose as the main sugar). The obtained hydrolysate was used as cultivation medium by Candidaguilliermondiiyeast in the raw form (containing 20 g/L xylose) and after concentration (85 g/L xylose), and the kinetic behavior of the yeast during Xylitol Production was evaluated in both media. Assays in semisynthetic media were also performed to compare the yeast performance in media without toxic compounds. According to the results, the kinetic behavior of the yeast cultivated in raw hydrolysate was as effective as in semisynthetic medium containing 20 g/L xylose. However, in concentrated hydrolysate medium, the Xylitol Production efficiency was 30.6% and 42.6% lower than in raw hydrolysate and semisynthetic medium containing 85 g/L xylose, respectively. In other words, the xylose-to-Xylitol bioconversion from hydrolysate medium was strongly affected when the initial xylose concentration was increased; however, similar behavior did not occur from semisynthetic media. The lowest efficiency of Xylitol Production from concentrated hydrolysate can be attributed to the high concentration of toxic compounds present in this medium, resulting from the hydrolysate concentration process.

  • establishment of the optimum initial xylose concentration and nutritional supplementation of brewer s spent grain hydrolysate for Xylitol Production by candida guilliermondii
    Process Biochemistry, 2008
    Co-Authors: Solange I. Mussatto, Inês Conceição Roberto
    Abstract:

    The effects of initial xylose concentration and nutritional supplementation of brewer's spent grain hydrolysate on Xylitol Production by Candida guilliermondii were evaluated using experimental design methodology. The hydrolysate containing 55, 75 or 95 g/l xylose, supplemented or not with nutrients (calcium chloride, ammonium sulfate and rice bran extract), was used as fermentation medium. The increase in Xylitol yield and productivity was related to the increase of initial xylose concentration, but up to a certain limit, above of which the yeast performance was not improved. The hydrolysate supplementation with nutrients did not interfere with xylose-to-Xylitol conversion. By using the statistic tool the best conditions for maximum Xylitol Production were found, which consisted in using the non-supplemented hydrolysate containing 70 g/l initial xylose concentration. Under these conditions, a Xylitol yield of 0.78 g/g and productivity of 0.58 g/(l h) were achieved.

  • enhanced Xylitol Production by precultivation of candida guilliermondii cells in sugarcane bagasse hemicellulosic hydrolysate
    Current Microbiology, 2006
    Co-Authors: Rita C L B Rodrigues, Inês Conceição Roberto, Luciane Sene, Gilvane S Matos, Adalberto Pessoa, Maria Das Graças De Almeida Felipe
    Abstract:

    The present work evaluated the key enzymes involved in Xylitol Production (xylose reductase [XR] and Xylitol dehydrogenase [XDH]) and their correlation with xylose, arabinose, and acetic acid assimilation during cultivation of Candida guilliermondii FTI 20037 cells in sugarcane bagasse hemicellulosic hydrolysate. For this purpose, inocula previously grown either in sugarcane bagasse hemicellulosic hydrolysate (SBHH) or in semidefined medium (xylose as a substrate) were used. The highest xylose/acetic acid consumption ratio (1.78) and the lowest arabinose consumption (13%) were attained in the fermentation using inoculum previously grown in semidefined medium (without acetic acid and arabinose). In this case, the highest values of XR (1.37 U mg prot−1) and XDH (0.91 U mg prot−1) activities were observed. The highest Xylitol yield (∼0.55 g g−1) and byproducts (ethanol and glycerol) formation were not influenced by inoculum procedure. However, the cell previously grown in the hydrolysate was effective in enhancing Xylitol Production by keeping the XR enzyme activity at high levels (around 0.99 U·mg prot −1 ), reducing the XDH activity (34.0%) and increasing Xylitol volumetric productivity (26.5%) with respect to the inoculum cultivated in semidefined medium. Therefore, inoculum adaptation to SBHH was shown to be an important strategy to improve Xylitol productivity.

Maria Das Graças De Almeida Felipe - One of the best experts on this subject based on the ideXlab platform.

  • Xylitol bioProduction state of the art industrial paradigm shift and opportunities for integrated biorefineries
    Critical Reviews in Biotechnology, 2019
    Co-Authors: Andres Felipe Hernandezperez, Silvio Silvério Da Silva, Luciane Sene, Priscila Vaz De Arruda, Anuj K Chandel, Maria Das Graças De Almeida Felipe
    Abstract:

    Recent advances in biomass conversion technologies have shown a promising future toward fermentation during Xylitol Production. Xylitol is one of the top 12 renewable added-value chemicals that can be obtained from biomass according to US Department of Energy (USDOE). Currently, Xylitol accounts for approximately US$823.6 million of annual sales in the market, and this amount is expected to reach US$1.37 billion by 2025. This high demand has been achieved owing to the chemical conversion of hemicellulosic hydrolysates from different lignocellulosic biomasses, which is a costly and non-ecofriendly process. Xylose-rich hemicellulosic hydrolysates are the major raw materials for Xylitol Production through either chemical or biotechnological routes. Economic Production of a clean hemicellulosic hydrolysate is one of the major bottlenecks for Xylitol Production on the commercial scale. Advancements in biotechnology, such as the isolation of novel microorganisms, genetic manipulation of xylose metabolizing strains, and modifications in the fermentation process, can enhance the economic feasibility of Xylitol Production on the large scale. Furthermore, Xylitol Production in integrated biorefineries can be even more economic, given the readily available raw materials and the co-use of steam, electricity, and water, among others. Exploring new biotechnology techniques in integrated biorefineries would open new markets and opportunities for sustainable Xylitol Production to fulfill the market's growing demands for this sugar alcohol. This article is a review of the advancements reported in the whole biotechnological process for Xylitol Production, and involve pretreatment technologies, hemicellulosic hydrolysate preparation, xylose conversion into Xylitol, and product recovery. Special attention is devoted to current metabolic engineering strategies to improve this bioprocess, as well as to the importance of Xylitol Production processes in biorefineries.

  • scale up of Xylitol Production from sugarcane bagasse hemicellulosic hydrolysate by candida guilliermondii fti 20037
    Journal of Industrial and Engineering Chemistry, 2017
    Co-Authors: Priscila Vaz De Arruda, Rita C L B Rodrigues, Julio Cesar Dos Santos, Debora Danielle Virginio Da Silva, Celina Kiyomi Yamakawa, George Jackson De Moraes Rocha, Jonas Nolasco, Jose Geraldo Da Cruz Pradella, Carlos Eduardo Vaz Rossell, Maria Das Graças De Almeida Felipe
    Abstract:

    Abstract In this study, volumetric oxygen mass transfer coefficient (kLa) was selected as a criterion for facilitating the scale up of Xylitol Production by Candida guilliermondii at the bench and pilot-scale level. A kLa value of 16 h−1 was applied in reactors with volumetric capacity of 2.4 L, 18 L and 125 L. Fermentation was successfully scaled-up from the bench to pilot-scale level with all experiments demonstrating a minimum of 60% xylose to Xylitol conversion efficiency. Under all evaluated conditions glycerol and ethanol were also produced as by-products of xylose metabolism. Only minor differences were observed in the fermentation profile when reactor volumes ranging from 2.4 L to 125 L were used for experimentation purposes, reaching, at pilot scale, yield and volumetric productivity of 0.55 g g−1 and 0.31 g L−1 h−1, respectively, with maximum specific growth rate of 0.26 h−1. This demonstrates and reinforces the feasibility of using kLa as scale up criterion. The use of this parameter allowed precise reProduction of results obtained at bench bioreactor level to a larger scale; this is extremely crucial and important information considering that the aim of the proposed biotechnological process is to reach the level required for the industrial viability.

  • sugarcane straw as a feedstock for Xylitol Production by candida guilliermondii fti 20037
    Brazilian Journal of Microbiology, 2016
    Co-Authors: Andres Felipe Hernandezperez, Priscila Vaz De Arruda, Maria Das Graças De Almeida Felipe
    Abstract:

    Sugarcane straw has become an available lignocellulosic biomass since the progressive introduction of the non-burning harvest in Brazil. Besides keeping this biomass in the field, it can be used as a feedstock in thermochemical or biochemical conversion processes. This makes feasible its incorporation in a biorefinery, whose economic profitability could be supported by integrated Production of low-value biofuels and high-value chemicals, e.g., Xylitol, which has important industrial and clinical applications. Herein, biotechnological Production of Xylitol is presented as a possible route for the valorization of sugarcane straw and its incorporation in a biorefinery. Nutritional supplementation of the sugarcane straw hemicellulosic hydrolyzate as a function of initial oxygen availability was studied in batch fermentation of Candida guilliermondii FTI 20037. The nutritional supplementation conditions evaluated were: no supplementation; supplementation with (NH4)2SO4, and full supplementation with (NH4)2SO4, rice bran extract and CaCl2·2H2O. Experiments were performed at pH 5.5, 30 °C, 200 rpm, for 48 h in 125 mL Erlenmeyer flasks containing either 25 or 50 mL of medium in order to vary initial oxygen availability. Without supplementation, complete consumption of glucose and partial consumption of xylose were observed. In this condition the maximum Xylitol yield (0.67 g g-1) was obtained under reduced initial oxygen availability. Nutritional supplementation increased xylose consumption and Xylitol Production by up to 200% and 240%, respectively. The maximum Xylitol volumetric productivity (0.34 g L-1 h-1) was reached at full supplementation and increased initial oxygen availability. The results demonstrated a combined effect of nutritional supplementation and initial oxygen availability on Xylitol Production from sugarcane straw hemicellulosic hydrolyzate.

  • biochemical conversion of sugarcane straw hemicellulosic hydrolyzate supplemented with co substrates for Xylitol Production
    Bioresource Technology, 2016
    Co-Authors: Andres Felipe Hernandezperez, Kelly J. Dussán, I A L Costa, Debora Danielle Virginio Da Silva, T R Villela, Eliana Vieira Canettieri, J A Carvalho, T Soares G Neto, Maria Das Graças De Almeida Felipe
    Abstract:

    Biotechnological Production of Xylitol is an attractive route to add value to a sugarcane biorefinery, through utilization of the hemicellulosic fraction of sugarcane straw, whose availability is increasing in Brazil. Herein, supplementation of the sugarcane straw hemicellulosic hydrolyzate (xylose 57gL(-1)) with maltose, sucrose, cellobiose or glycerol was proposed, and their effect as co-substrates on Xylitol Production by Candida guilliermondii FTI 20037 was studied. Sucrose (10gL(-1)) and glycerol (0.7gL(-1)) supplementation led to significant increase of 8.88% and 6.86% on xylose uptake rate (1.11gL(-1)h(-1) and 1.09gL(-1)), respectively, but only with sucrose, significant increments of 12.88% and 8.69% on final Xylitol concentration (36.11gL(-1)) and volumetric productivity (0.75gL(-1)h(-1)), respectively, were achieved. Based on these results, utilization of complex sources of sucrose, derived from agro-industries, as nutritional supplementation for Xylitol Production can be proposed as a strategy for improving the yeast performance and reducing the cost of this bioprocess by replacing more expensive nutrients.

  • evaluation of hexose and pentose in pre cultivation of candida guilliermondii on the key enzymes for Xylitol Production in sugarcane hemicellulosic hydrolysate
    Biodegradation, 2011
    Co-Authors: Priscila Vaz De Arruda, Debora Danielle Virginio Da Silva, Rita C L B Rodrigues, Maria Das Graças De Almeida Felipe
    Abstract:

    The evaluation of hexose and pentose in pre-cultivation of Candida guilliermondii FTI 20037 yeast on xylose reductase (XR) and Xylitol dehydrogenase (XDH) enzymes activities was performed during fermentation in sugarcane bagasse hemicellulosic hydrolysate. The Xylitol Production was evaluated by using cells previously growth in 30.0 gl−1 xylose, 30.0 gl−1 glucose and in both sugars mixture (30.0 gl−1 xylose and 2.0 gl−1 glucose). The vacuum evaporated hydrolysate (80 gl−1) was detoxificated by ion exchange resin (A-860S; A500PS and C-150-Purolite®). The total phenolic compounds and acetic acid were 93.0 and 64.9%, respectively, removed by the resin hydrolysate treatment. All experiments were carried out in Erlenmeyer flasks at 200 rpm, 30°C. The maximum XR (0.618 Umg Prot −1 ) and XDH (0.783 Umg Prot −1 ) enzymes activities was obtained using inoculum previously growth in both sugars mixture. The highest cell concentration (10.6 gl−1) was obtained with inoculum pre-cultivated in the glucose. However, the Xylitol yield and Xylitol volumetric productivity were favored using the xylose as carbon source. In this case, it was observed maximum xylose (81%) and acetic acid (100%) consumption. It is very important to point out that maximum enzymatic activities were obtained when the mixture of sugars was used as carbon source of inoculum, while the highest fermentative parameters were obtained when xylose was used.

Attilio Converti - One of the best experts on this subject based on the ideXlab platform.

  • use of response surface methodology for optimization of Xylitol Production by the new yeast strain debaryomyces hansenii ufv 170
    Journal of Food Engineering, 2006
    Co-Authors: Fabio Coelho Sampaio, Danilo De Faveri, Patrizia Perego, Flávia Maria Lopes Passos, Hilario Cuquetto Mantovani, Attilio Converti
    Abstract:

    Abstract Aim of this work was the optimization of Xylitol Production by Debaryomyces hansenii UFV-170, which already proved to be a new promising Xylitol-producing yeast. Two sets of batch bioconversion tests were carried out on synthetic medium, according to two joined 3 3 and 3 2 type full factorial designs, selecting the initial xylose concentration ( S 0 ), rotational speed ( v ) and starting biomass concentration ( X 0 ) as independent variables and the maximum Xylitol concentration ( P ), Xylitol yield on consumed xylose ( Y P / S ), volumetric productivity ( Q P ) and specific productivity ( q P ) as response variables. The collected results were then worked out by response surface methodology (RSM). Overall optimization, conducted by overlaying the curves of the responses under investigation, allowed us to point out an optimal range of the independent variables within which the four responses were simultaneously optimized. The point chosen as representative of this optimal area corresponded to S 0  = 156 g L −1 , v  = 280 rpm and X 0  = 6.4 g L −1 , conditions under which the model predicted P  = 116.25 g L −1 , Y P / S  = 0.77 g g −1 , Q P  = 1.49 g L −1  h −1 and q P  = 0.16 g g −1  h −1 .

  • Xylitol Production from sugarcane bagasse hydrolysate metabolic behaviour of candida guilliermondii cells entrapped in ca alginate
    Biochemical Engineering Journal, 2005
    Co-Authors: Walter Carvalho, Patrizia Perego, Larissa Canilha, Silvio Silvério Da Silva, Julio Dos C Santos, Attilio Converti
    Abstract:

    Abstract Sugarcane bagasse hydrolysate was used for batch Xylitol Production in stirred tank reactor with Candida guilliermondii cells entrapped in Ca-alginate beads. Experiments were carried out using five-fold concentrated hydrolysate, agitation speed of 300 rpm, air flowrate of 1.3 l min−1, initial cell concentration of 1.4 gDM l−1, and starting pH 6.0. Xylitol Production reached 47.5 g l−1 within 120 h of fermentation, resulting in a bioconversion yield of 0.81 g g−1 and a productivity of 0.40 g l−1 h−1. The metabolic behaviour of C. guilliermondii was then investigated through material balances using the concentrations of consumed substrates and formed products and assuming that xylose was simultaneously assimilated by the yeast for anaerobic and semi-aerobic Xylitol Productions, complete oxidation by the TCA cycle and cell growth. Data collected at different times were finally used to estimate the overall ATP requirements for biomass growth and maintenance. The energy expenditure increased from 2.1 to 6.6 mo l ATP C mo l DM − 1 throughout the fermentation, highlighting a progressive difficulty of the microbial system in facing the energy needs of its semi-aerobic metabolism.

  • evaluation of porous glass and zeolite as cells carriers for Xylitol Production from sugarcane bagasse hydrolysate
    Biochemical Engineering Journal, 2005
    Co-Authors: Julio Cesar Dos Santos, Attilio Converti, Solange I. Mussatto, Giuliano Dragone, Silvio Silvério Da Silva
    Abstract:

    Abstract Adsorbing carriers for immobilisation of Candida guilliermondii cells to use for Xylitol Production from sugarcane bagasse hemicellulose hydrolysate were tested. Biomass was immobilised in situ by natural adsorption, i.e. through direct contact between cells for the inoculum and carrier particles at the beginning of fermentations. The carriers employed were: Syrane porous glass beads with 2.53 mm diameter in average and pore diameter in the range 60–300 μm, supplied by Bioengineering (Wald, Switzerland), and NaX zeolite UOP WE 894 purchased from Plury Quimica S.A. (Diadema, SP, Brazil). At the end of the run with free cells taken as a reference test, Xylitol concentration (Pf) achieved 35.5 g/l, corresponding to a xylose-to-Xylitol yield factor (YP/S) of 0.72 g/g and a volumetric productivity (QP) of 0.49 g/l h, while final cell concentration (Xf) and productivity (Qx) were only 5.32 g/l and 0.048 g/l h, respectively. Both systems with immobilised cells exhibited lower Xylitol Productions (Pf = 28.8–29.5 g/l, YP/S = 0.52–0.53 g/g, QP = 0.32–0.33 g/l h) and higher cell growth, with particular concern to porous glass (Xf = 10.5 g/l, Qx = 0.10 g/l h). Electronic microscopy observations demonstrated that the excellent performance of porous glass as cell support was due to the development of a thick extracellular matrix either within the large pores or on the surface of this material. As a consequence, almost 50% of the cells resulted to be adsorbed to the carrier at the end of the run. This growth was also responsible for a decrease in the fraction of xylose available for Xylitol Production. Employing zeolite, a material with pore size smaller than cell size, immobilised cells represented only 30% of the final population and immobilisation was just observed on the carrier surface. The low cell attachment on this material can be explained by the stress exerted on the outer immobilised cells by the friction among beads.

  • statistical investigation on the effects of starting xylose concentration and oxygen mass flowrate on Xylitol Production from rice straw hydrolyzate by response surface methodology
    Journal of Food Engineering, 2004
    Co-Authors: Danilo De Faveri, Paolo Torre, Patrizia Perego, Attilio Converti
    Abstract:

    Abstract A 3 2 full-factorial design combined with response surface methodology was used to investigate the simultaneous effects of starting xylose concentration ( S 0 ) and oxygen mass flowrate ( q O 2 ) on Xylitol Production from rice straw hydrolyzate. Fermentations were performed at 30 °C, using Debaryomyces hansenii NRRL Y-7426 as Xylitol producer and varying S 0 between 50 and 150 g/l and q O 2 between 2.5 and 5.9 mg O 2 /s. At the lowest starting xylose concentration and an oxygen mass flowrate of 4.2 mg O 2 /s, volumetric productivity and Xylitol yield reached maximum values ( Q p =0.70 g P /l h and Y P/S =0.73 g P /g S , respectively), but Xylitol concentration was quite low (35.9 g P /l). The results were in close agreement with the model prediction. The statistical model also allowed identifying the optimum operating conditions ( S 0 =71 g/l and q O 2 =4.1 mg O 2 /s) able to simultaneously maximize volumetric productivity (0.53 g P /l h), Xylitol yield (0.71 g P /g S ) and final Xylitol concentration (42.2 g P /l).

  • Xylitol Production by ca alginate entrapped cells comparison of different fermentation systems
    Enzyme and Microbial Technology, 2003
    Co-Authors: Walter Carvalho, Silvio Silvério Da Silva, Julio Cesar Dos Santos, Attilio Converti
    Abstract:

    Abstract Candida guilliermondii cells were entrapped in Ca-alginate beads and used for Xylitol Production from concentrated sugarcane bagasse hemicellulosic hydrolysate in three different fermentation systems, namely 125-ml Erlenmeyer flasks (EF), 2.4-l stirred tank reactor (STR) and 2.4-l basket-type stirred tank reactor (BSTR). The EF system provided a Xylitol Production of 21.0 g P  l −1 , a product yield based on xylose consumption of 0.54 g P  g S −1 , and an overall Production rate of 0.44 g P  l −1  h −1 after 48 h of fermentation. By the STR system, 23.5 g P  l −1 was produced after 60 h of fermentation, corresponding to a yield of 0.58 g P  g S −1 and a Production rate of 0.39 g P  l −1  h −1 . As the average volume of the beads decreased by 10.7% ( p P  g S −1 ), Production rate (0.21 g P  l −1  h −1 ) and concentration (15.0 g P  l −1 ) attained by this system were affected by mass-transfer limitations.

Silvio Silvério Da Silva - One of the best experts on this subject based on the ideXlab platform.

  • Xylitol bioProduction state of the art industrial paradigm shift and opportunities for integrated biorefineries
    Critical Reviews in Biotechnology, 2019
    Co-Authors: Andres Felipe Hernandezperez, Silvio Silvério Da Silva, Luciane Sene, Priscila Vaz De Arruda, Anuj K Chandel, Maria Das Graças De Almeida Felipe
    Abstract:

    Recent advances in biomass conversion technologies have shown a promising future toward fermentation during Xylitol Production. Xylitol is one of the top 12 renewable added-value chemicals that can be obtained from biomass according to US Department of Energy (USDOE). Currently, Xylitol accounts for approximately US$823.6 million of annual sales in the market, and this amount is expected to reach US$1.37 billion by 2025. This high demand has been achieved owing to the chemical conversion of hemicellulosic hydrolysates from different lignocellulosic biomasses, which is a costly and non-ecofriendly process. Xylose-rich hemicellulosic hydrolysates are the major raw materials for Xylitol Production through either chemical or biotechnological routes. Economic Production of a clean hemicellulosic hydrolysate is one of the major bottlenecks for Xylitol Production on the commercial scale. Advancements in biotechnology, such as the isolation of novel microorganisms, genetic manipulation of xylose metabolizing strains, and modifications in the fermentation process, can enhance the economic feasibility of Xylitol Production on the large scale. Furthermore, Xylitol Production in integrated biorefineries can be even more economic, given the readily available raw materials and the co-use of steam, electricity, and water, among others. Exploring new biotechnology techniques in integrated biorefineries would open new markets and opportunities for sustainable Xylitol Production to fulfill the market's growing demands for this sugar alcohol. This article is a review of the advancements reported in the whole biotechnological process for Xylitol Production, and involve pretreatment technologies, hemicellulosic hydrolysate preparation, xylose conversion into Xylitol, and product recovery. Special attention is devoted to current metabolic engineering strategies to improve this bioprocess, as well as to the importance of Xylitol Production processes in biorefineries.

  • profiles of xylose reductase Xylitol dehydrogenase and Xylitol Production under different oxygen transfer volumetric coefficient values
    Journal of Chemical Technology & Biotechnology, 2009
    Co-Authors: Ricardo De Freitas Branco, Boutros Fouad Sarrouh, Julio Cesar Dos Santos, Adalberto Pessoa, Juan Daniel Rivaldi, Silvio Silvério Da Silva
    Abstract:

    BACKGROUND: Xylitol is a sugar alcohol (polyalcohol) with many interesting properties for pharmaceutical and food products. It is currently produced by a chemical process, which has some disadvantages such as high energy requirement. Therefore microbiological Production of Xylitol has been studied as an alternative, but its viability is dependent on optimisation of the fermentation variables. Among these, aeration is fundamental, because Xylitol is produced only under adequate oxygen availability. In most experiments with Xylitol-producing yeasts, low oxygen transfer volumetric coefficient (KLa) values are used to maintain microaerobic conditions. However, in the present study the use of relatively high KLa values resulted in high Xylitol Production. The effect of aeration was also evaluated via the profiles of xylose reductase (XR) and Xylitol dehydrogenase (XD) activities during the experiments. RESULTS: The highest XR specific activity (1.45 ± 0.21 U mgprotein−1) was achieved during the experiment with the lowest KLa value (12 h−1), while the highest XD specific activity (0.19 ± 0.03 U mgprotein−1) was observed with a KLa value of 25 h−1. Xylitol Production was enhanced when KLa was increased from 12 to 50 h−1, which resulted in the best condition observed, corresponding to a Xylitol volumetric productivity of 1.50 ± 0.08 gXylitol L−1 h−1 and an efficiency of 71 ± 6.0%. CONCLUSION: The results showed that the enzyme activities during Xylitol bioProduction depend greatly on the initial KLa value (oxygen availability). This finding supplies important information for further studies in molecular biology and genetic engineering aimed at improving Xylitol bioProduction. Copyright © 2008 Society of Chemical Industry

  • Xylitol Production from sugarcane bagasse hydrolysate metabolic behaviour of candida guilliermondii cells entrapped in ca alginate
    Biochemical Engineering Journal, 2005
    Co-Authors: Walter Carvalho, Patrizia Perego, Larissa Canilha, Silvio Silvério Da Silva, Julio Dos C Santos, Attilio Converti
    Abstract:

    Abstract Sugarcane bagasse hydrolysate was used for batch Xylitol Production in stirred tank reactor with Candida guilliermondii cells entrapped in Ca-alginate beads. Experiments were carried out using five-fold concentrated hydrolysate, agitation speed of 300 rpm, air flowrate of 1.3 l min−1, initial cell concentration of 1.4 gDM l−1, and starting pH 6.0. Xylitol Production reached 47.5 g l−1 within 120 h of fermentation, resulting in a bioconversion yield of 0.81 g g−1 and a productivity of 0.40 g l−1 h−1. The metabolic behaviour of C. guilliermondii was then investigated through material balances using the concentrations of consumed substrates and formed products and assuming that xylose was simultaneously assimilated by the yeast for anaerobic and semi-aerobic Xylitol Productions, complete oxidation by the TCA cycle and cell growth. Data collected at different times were finally used to estimate the overall ATP requirements for biomass growth and maintenance. The energy expenditure increased from 2.1 to 6.6 mo l ATP C mo l DM − 1 throughout the fermentation, highlighting a progressive difficulty of the microbial system in facing the energy needs of its semi-aerobic metabolism.

  • evaluation of porous glass and zeolite as cells carriers for Xylitol Production from sugarcane bagasse hydrolysate
    Biochemical Engineering Journal, 2005
    Co-Authors: Julio Cesar Dos Santos, Attilio Converti, Solange I. Mussatto, Giuliano Dragone, Silvio Silvério Da Silva
    Abstract:

    Abstract Adsorbing carriers for immobilisation of Candida guilliermondii cells to use for Xylitol Production from sugarcane bagasse hemicellulose hydrolysate were tested. Biomass was immobilised in situ by natural adsorption, i.e. through direct contact between cells for the inoculum and carrier particles at the beginning of fermentations. The carriers employed were: Syrane porous glass beads with 2.53 mm diameter in average and pore diameter in the range 60–300 μm, supplied by Bioengineering (Wald, Switzerland), and NaX zeolite UOP WE 894 purchased from Plury Quimica S.A. (Diadema, SP, Brazil). At the end of the run with free cells taken as a reference test, Xylitol concentration (Pf) achieved 35.5 g/l, corresponding to a xylose-to-Xylitol yield factor (YP/S) of 0.72 g/g and a volumetric productivity (QP) of 0.49 g/l h, while final cell concentration (Xf) and productivity (Qx) were only 5.32 g/l and 0.048 g/l h, respectively. Both systems with immobilised cells exhibited lower Xylitol Productions (Pf = 28.8–29.5 g/l, YP/S = 0.52–0.53 g/g, QP = 0.32–0.33 g/l h) and higher cell growth, with particular concern to porous glass (Xf = 10.5 g/l, Qx = 0.10 g/l h). Electronic microscopy observations demonstrated that the excellent performance of porous glass as cell support was due to the development of a thick extracellular matrix either within the large pores or on the surface of this material. As a consequence, almost 50% of the cells resulted to be adsorbed to the carrier at the end of the run. This growth was also responsible for a decrease in the fraction of xylose available for Xylitol Production. Employing zeolite, a material with pore size smaller than cell size, immobilised cells represented only 30% of the final population and immobilisation was just observed on the carrier surface. The low cell attachment on this material can be explained by the stress exerted on the outer immobilised cells by the friction among beads.

  • Xylitol Production by ca alginate entrapped cells comparison of different fermentation systems
    Enzyme and Microbial Technology, 2003
    Co-Authors: Walter Carvalho, Silvio Silvério Da Silva, Julio Cesar Dos Santos, Attilio Converti
    Abstract:

    Abstract Candida guilliermondii cells were entrapped in Ca-alginate beads and used for Xylitol Production from concentrated sugarcane bagasse hemicellulosic hydrolysate in three different fermentation systems, namely 125-ml Erlenmeyer flasks (EF), 2.4-l stirred tank reactor (STR) and 2.4-l basket-type stirred tank reactor (BSTR). The EF system provided a Xylitol Production of 21.0 g P  l −1 , a product yield based on xylose consumption of 0.54 g P  g S −1 , and an overall Production rate of 0.44 g P  l −1  h −1 after 48 h of fermentation. By the STR system, 23.5 g P  l −1 was produced after 60 h of fermentation, corresponding to a yield of 0.58 g P  g S −1 and a Production rate of 0.39 g P  l −1  h −1 . As the average volume of the beads decreased by 10.7% ( p P  g S −1 ), Production rate (0.21 g P  l −1  h −1 ) and concentration (15.0 g P  l −1 ) attained by this system were affected by mass-transfer limitations.

Patrick C Cirino - One of the best experts on this subject based on the ideXlab platform.

  • improved nadph supply for Xylitol Production by engineered escherichia coli with glycolytic mutations
    Biotechnology Progress, 2011
    Co-Authors: Jonathan W Chin, Patrick C Cirino
    Abstract:

    Escherichia coli engineered to uptake xylose while metabolizing glucose was previously shown to produce high levels of Xylitol from a mixture of glucose and xylose when expressing NADPH-dependent xylose reductase from Candida boidinii (CbXR) (Cirino et al., Biotechnol Bioeng. 2006;95:1167-1176). We then described the effects of deletions of key metabolic pathways (e.g., Embden–Meyerhof–Parnas and pentose phosphate pathway) and reactions (e.g., transhydrogenase and NADH dehydrogenase) on resting-cell Xylitol yield (YRPG: moles of Xylitol produced per mole of glucose consumed) (Chin et al., Biotechnol Bioeng. 2009;102:209-220). These prior results demonstrated the importance of direct NADPH supply by NADP+-utilizing enzymes in central metabolism for driving heterologous NADPH-dependent reactions. This study describes strain modifications that improve coupling between glucose catabolism (oxidation) and xylose reduction using two fundamentally different strategies. We first examined the effects of deleting the phosphofructokinase (pfk) gene(s) on growth-uncoupled Xylitol Production and found that deleting both pfkA and sthA (encoding the E. coli-soluble transhydrogenase) improved the Xylitol YRPG from 3.4 ± 0.6 to 5.4 ± 0.4. The second strategy focused on coupling aerobic growth on glucose to Xylitol Production by deleting pgi (encoding phosphoglucose isomerase) and sthA. Impaired growth due to imbalanced NADPH metabolism (Sauer et al., J Biol Chem. 2004;279:6613-6619) was alleviated upon expressing CbXR, resulting in Xylitol Production similar to that of the growth-uncoupled precursor strains but with much less acetate secretion and more efficient utilization of glucose. Intracellular nicotinamide cofactor levels were also quantified, and the magnitude of the change in the NADPH/NADP+ ratio measured from cells consuming glucose in the absence vs. presence of xylose showed a strong correlation to the resulting YRPG. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011

  • anaerobic obligatory Xylitol Production in escherichia coli strains devoid of native fermentation pathways
    Applied and Environmental Microbiology, 2011
    Co-Authors: Olubolaji Akinterinwa, Patrick C Cirino
    Abstract:

    Microorganisms are attractive hosts for NAD(P)H-dependent biocatalysis due to advantages that include the ability to regenerate cofactors in vivo via metabolism of abundant raw materials (e.g., glucose). However, challenges lie in properly constraining metabolism for implementing whole-cell transformations such that reduced cofactors are effectively utilized to drive the reactions of interest. We previously engineered Escherichia coli to produce Xylitol from glucose-xylose mixtures by heterologous expression of NADPH-dependent xylose reductase from Candida boidinii (CbXR) (7). In this system, aerobic glucose catabolism to carbon dioxide provides NADPH for xylose reduction to Xylitol. Similar to other reports on NAD(P)H-dependent biotransformations catalyzed by heterologous enzymes in E. coli, the quantity of reducing equivalents used for Xylitol Production is maximally ∼60% of the theoretical maximum value under nongrowing conditions (3, 4, 6, 21). The disparity between the experimental and theoretical yields (yield is defined as moles of reduced product per mole of glucose consumed and denoted “YRPG”) has been suggested to result from various factors, including the inability of the heterologous enzyme and/or transhydrogenases to effectively compete with other cofactor-utilizing cellular reactions, such as those involved in aerobic respiration (3, 6). Decreasing aeration or deleting NADH dehydrogenase-encoding genes results in incomplete glucose oxidation and the secretion of pyruvate and fermentation products (6, 7). Here, we describe an alternate, anaerobic strategy of coupling NADPH-dependent xylose reduction to cofactor regeneration via glucose oxidation (depicted in Fig. ​Fig.1).1). Fermentation pathways were eliminated so that Xylitol Production serves as the sole means of regenerating NAD+ and maintaining redox balance. The expression of a variant of lipoamide dehydrogenase (LPD) conferring reduced sensitivity of the pyruvate dehydrogenase complex (PDH) to NADH (15) resulted in the reduction of ∼4 moles of xylose to Xylitol per mole of glucose metabolized to acetate. The deletion of pntA, encoding a subunit of the membrane-bound transhydrogenase (PntAB), resulted in a more than 50% decrease in the Xylitol yield. FIG. 1. Anaerobic Xylitol Production in engineered E. coli. Glucose conversion to acetate serves as the source of reducing power for xylose reduction to Xylitol by heterologously expressed, NADPH-dependent xylose reductase (CbXR). Reducing equivalents are transferred ... The strains used in this study are listed in Table ​Table1.1. PCRs and gene cloning were performed following standard protocols (16, 18) and as previously described (6; J. W. Chin and P. C. Cirino, submitted for publication). The CbXR gene was inserted into the E. coli chromosome at the phage HK022 attachment site as described previously (11; Chin and Cirino, submitted for publication). E. coli K-12 strains with single gene deletions carrying an FLP recombination target (FRT)-flanked kanamycin resistance cassette in place of the selected gene (ldhA, adhE, frdA, pntA, or sthA) were obtained from the Keio collection (2). The multigene deletions Δzwf-eda and ΔxylAB originated from strains JC68 (6) and JC82 (precursor for strain OA24 [1]), respectively. Subsequent strains were created via phage P1 transductions followed by flippase recombinase-mediated excision of the corresponding antibiotic resistance marker gene (8). TABLE 1. Strains used in this study

  • heterologous expression of d xylulokinase from pichia stipitis enables high levels of Xylitol Production by engineered escherichia coli growing on xylose
    Metabolic Engineering, 2009
    Co-Authors: Olubolaji Akinterinwa, Patrick C Cirino
    Abstract:

    Abstract Deletion of the Escherichia coli xylulokinase gene (xylB) is essential for achieving high Xylitol titers from Xylitol-producing E. coli strains growing on glucose in the presence of xylose. Our study suggests that this is due to XylB-catalyzed toxic synthesis of Xylitol-phosphate. This activity prohibits the use of xylose as the sole carbon source during Xylitol Production by E. coli. To overcome this limitation we turned to the yeast Pichia stipitis, which naturally produces Xylitol, as a source of xylulokinase (Xyl3). We examined the effects of plasmid-based expression of Xyl3 versus XylB on growth and Xylitol Production by engineered E. coli strains. Xylulokinase activity assays show similar levels of functional expression of both enzymes (determined as activity on xylulose), and reveal significantly more activity on Xylitol by XylB compared to Xyl3. 31P NMR confirms the Production of Xylitol-phosphate from in vitro reactions with XylB. Lastly, the replacement of xylB with XYL3 results in drastically enhanced Xylitol titers from E. coli strains co-expressing xylose reductase during growth on xylose.

  • analysis of nadph supply during Xylitol Production by engineered escherichia coli
    Biotechnology and Bioengineering, 2009
    Co-Authors: Jonathan W Chin, Reza Khankal, Caroline Monroe, Costas D Maranas, Patrick C Cirino
    Abstract:

    Escherichia coli strain PC09 (DxylB, cAMP- independent CRP (crp � ) mutant) expressing an NADPH- dependent xylose reductase from Candida boidinii (CbXR) was previously reported to produce Xylitol from xylose while metabolizing glucose (Cirino et al. (2006) Biotechnol Bioeng 95(6): 1167-1176). This study aims to understand the role of NADPH supply in Xylitol yield and the contribution of key central carbon metabolism enzymes toward Xylitol produc- tion. Studies in which the expression of CbXR or a xylose transporter was increased suggest that enzyme activity and xylose transport are not limiting Xylitol Production in PC09. A constraints-based stoichiometric metabolic network model was used to understand the roles of central carbon metabolism reactions and xylose transport energetics on the theoretical maximum molar Xylitol yield (Xylitol produced per glucose consumed), and Xylitol yields (YRPG) were measured from resting cell biotransformations with various PC09 derivative strains. For the case of xylose-proton sym- port, omitting the Zwf (glucose-6-phosphate dehydrogen- ase) or PntAB (membrane-bound transhydrogenase) reactions or TCA cycle activity from the model reduces the theoretical maximum yield from 9.2 to 8.8, 3.6, and 8.0 mol Xylitol (mol glucose) � 1 , respectively. Experimentally, deleting pgi (encoding phosphoglucose isomerase) from strain PC09 improves the yield from 3.4 to 4.0 mol Xylitol (mol glucose) � 1 , while deleting either or both E. coli trans- hydrogenases (sthA and pntA) has no significant effect on the measured yield. Deleting either zwf or sucC (TCA cycle) significantly reduces the yield from 3.4 to 2.0 and 2.3 mol Xylitol (mol glucose) � 1 , respectively. Expression of a xylose reductase with relaxed cofactor specificity increases the yield to 4.0. The large discrepancy between theoretical maximum and experimentally determined yield values suggests that biocatalysis is compromised by pathways competing for reducing equivalents and dissipating energy. The metabolic role of transhydrogenases during E. coli biocatalysis has remained largely unspecified. Our results demonstrate the importance of direct NADPH supply by NADP þ -utilizing enzymes in central metabolism for driving heterologous NADPH-dependent reactions, and suggest that the pool of reduced cofactors available for biotransformation is not readily interchangeable via transhydrogenase. Biotechnol. Bioeng. 2009;102: 209-220. 2008 Wiley Periodicals, Inc.

  • role of xylose transporters in Xylitol Production from engineered escherichia coli
    Journal of Biotechnology, 2008
    Co-Authors: Reza Khankal, Jonathan W Chin, Patrick C Cirino
    Abstract:

    Abstract Escherichia coli W3110 was previously engineered to co-utilize glucose and xylose by replacing the wild-type crp gene with a crp* mutant encoding a cAMP-independent CRP variant (Cirino et al., 2006 [Cirino, P.C., Chin, J.W., Ingram, L.O., 2006. Engineering Escherichia coli for Xylitol Production from glucose–xylose mixtures. Biotechnol. Bioeng. 95, 1167–1176.]). Subsequent deletion of the xylB gene (encoding xylulokinase) and expression of xylose reductase from Candida boidinii (CbXR) resulted in a strain which produces Xylitol from glucose–xylose mixtures. In this study we examine the contributions of the native E. coli xylose transporters (the d -xylose/proton symporter XylE and the d -xylose ABC transporter XylFGH) and CRP* to Xylitol Production in the presence of glucose and xylose. The final batch Xylitol titer with strain PC09 (ΔxylB and crp*) is reduced by 40% upon deletion of xylG and by 60% upon deletion of both xyl transporters. Xylitol Production by the wild-type strain (W3110) expressing CbXR is not reduced when xylE and xylG are deleted, demonstrating tight regulation of the xylose transporters by CRP and revealing significant secondary xylose transport. Finally, plasmid expression of XylE or XylFGH with CbXR in PC07 (ΔxylB and wild-type crp) growing on glucose results in Xylitol titers similar to that achieved with PC09 and provides an alternative strategy to the use of CRP*.