The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Chun Zhao Liu - One of the best experts on this subject based on the ideXlab platform.
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Coproduction of hydrogen and volatile fatty acids via integrated two-step fermentation of sweet Sorghum Stalks by alkaline and enzymatic treatment
Biomass and Bioenergy, 2021Co-Authors: Saiful Islam, Chen Guo, Zeju Zhang, Chun‐lei Liu, Chun Zhao LiuAbstract:Abstract Coproduction of H2 and volatile fatty acids from sweet Sorghum Stalks was successfully developed via two-step fermentation process involving alkaline and enzymatic treatment of the residual slurry obtained from the first step fermentation of the raw material. The optimum treatment conditions to obtain the highest yield of the end products included 2% (w/v) alkali at 120 °C for the residual slurry and 32 FPU cellulase per gram of the alkali-treated materials. The two-step fermentation using Clostridium thermosaccharolyticum increased the end product yields of H2 (6.37 mmol/g-substrate) by 95%, acetic acid (2.33 g/L) by 97% and butyric acid (2.36 g/L) by 143% compared with those obtained in the single step fermentation without any treatment. As a result, the H2 energy recovery efficiency of the two-step fermentation process with commercially attractive butyric acid as a coproduct reached 10.54%. These results provide a promising approach for sweet Sorghum biorefining.
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Enhanced hydrogen and volatile fatty acid production from sweet Sorghum Stalks by two-steps dark fermentation with dilute acid treatment in between
International Journal of Hydrogen Energy, 2018Co-Authors: Md Saiful Islam, Chen Guo, Chun Zhao LiuAbstract:This study investigated the potential of hydrogen and volatile fatty acid coproduction from two steps dark fermentation with dilute acid treatments of the residual slurry after 1st step fermentation. Sweet Sorghum Stalks (SS) was used as substrate along with Clostridium thermosaccharolyticum as production microbe. Residual lignocelluloses after 1st step fermentation were treated for 1 h by sulfuric acid concentration of 0.25, 0.5, 1.0, 1.5, 2.0 and 2.5% (w/v) with different reaction temperature of 120, 90 and 60 °C were studied. The optimum severity conditions for the highest yield of products found from the treatment acid concentration of 1.5% (w/v) at 120 °C for 10 g/L of substrate concentration. Experimental data showed that two-step fermentation increased 76% hydrogen, 84% acetic acid and 113% of butyric acid production from single step. Maximum yields of hydrogen, acetic acid and butyric acid were 5.77 mmol/g-substrate, 2.17 g/L and 2.07 g/L respectively. This two-step fermentation for hydrogen and VFA production using the whole slurry would be a promising approach to SS biorefinery.
Leonidas Matsakas - One of the best experts on this subject based on the ideXlab platform.
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single cell oil and ethanol production by the oleaginous yeast trichosporon fermentans utilizing dried sweet Sorghum Stalks
Renewable Energy, 2020Co-Authors: Io Antonopoulou, Athanasios Spanopoulos, Leonidas MatsakasAbstract:Abstract The ability of the oleaginous yeast Trichosporon fermentans to efficiently produce lipids when cultivated in dried sweet Sorghum was evaluated. First, lipid production was evaluated in synthetic media mimicking the composition of sweet Sorghum Stalks and optimized based on the nitrogen source and C: N ratio. Under optimum conditions, the lipid production reached 3.66 g/L with 21.91% w/w lipid content by using a mixture of sucrose, glucose and fructose and peptone at C: N ratio 160. Cultivation on pre-saccharified sweet Sorghum Stalks offered 1.97 g/L, while it was found that sweet Sorghum Stalks can support yeast growth and lipid production without the need for external nitrogen source addition. At an attempt to increase the carbon source concentration for optimizing lipid production, the Crabtree effect was observed in T. fermentans. To this end, the yeast was evaluated for its potential to produce ethanol under anaerobic conditions in synthetic media and sweet Sorghum. The ethanol concentration at 100 g/L glucose was 40.31 g/L, while utilizing sweet Sorghum by adding a distinct saccharification step and external nitrogen source offered ethanol concentration equal to 23.5 g/L. To the authors’ knowledge, this is the first time that the Crabtree effect is observed in T. fermentans.
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Direct electricity generation from sweet Sorghum Stalks and anaerobic sludge
Industrial Crops and Products, 2017Co-Authors: Magnus Sjöblom, Leonidas Matsakas, Ulrika Rova, Adolf Krige, Paul ChristakopoulosAbstract:Abstract Dried sweet Sorghum Stalks were valorized as a raw material for electricity generation in a two chamber microbial fuel cell using anaerobic sludge from a biogas plant as inoculum. The maximum voltage obtained on the Sorghum Stalks at an operating temperature of 35 °C was 546 mV with a maximum power- and current density of 131 mW/m2 and 543 mA/m2, respectively. The coulombic efficiency was 2.2%. Polarization data indicated that Ohmic resistances were dominant with an internal resistance of 182 Ω. The total electrical energy per gram of dried Sorghum Stalks was 165 J/g. Enzymatic treatment of the Sorghum Stalks did not improve the total electrical energy obtained. A metabolic study demonstrated that the sugars were quickly fermented to formate, acetate, propionate, lactate and butyrate with acetate and butyrate being the dominant acids during electricity generation.
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Effect of synthetic and natural media on lipid production from Fusarium oxysporum
Elsevier, 2017Co-Authors: Leonidas Matsakas, Maria Giannakou, Dimitrij VörösAbstract:Background: Dependence on fossil resources, for the production of fuels and energy, has resulted in environmental and financial problems, which require our immediate action in order to reverse the situation. Use of renewable sources for the production of fuels and energy is an important alternative with biodiesel remains as one of the promising options. Aim of this work is to evaluate the fungus Fusarium oxysporum for its potentials to accumulate microbial lipids when grown on synthetic media and saccharified sweet Sorghum Stalks. Results: The effect of different carbon sources, nitrogen sources and C/N ratio on the lipid production was initially examined, which resulted in a lipid concentration of 4.4 g/L, with lipid content of 42.6% w/w. Sweet Sorghum Stalks were able to support growth and lipid production of the fungus, both as carbon source and as nitrogen source. It was also shown that saccharification of the dried Stalks is an important step to increase lipid production. Removal of the remaining stalk solids enabled the lipid production during cultivation in increased initial solids of up to 16 w/w. This resulted in a lipid production of 3.81 g/L. Conclusions: It was demonstrated that F. oxysporum can be used as an efficient oleaginous microorganism, with sweet Sorghum serving as an excellent raw material for the cultivation of the fungus. The lipids obtained during this work were also found to have a fatty acid profile with good potentials to be used for biodiesel production
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high concentrations of dried Sorghum Stalks as a biomass feedstock for single cell oil production by rhodosporidium toruloides
Biotechnology for Biofuels, 2015Co-Authors: Leonidas Matsakas, Ulrika Rova, Nemailla Bonturi, Everson Alves Miranda, Paul ChristakopoulosAbstract:Background Environmental crisis and concerns for energy security have made the research for renewable fuels that will substitute the usage of fossil fuels an important priority. Biodiesel is a potential substitute for petroleum, but its feasibility is hindered by the utilization of edible vegetable oil as raw material, which is responsible for a large fraction of the production cost and fosters the food versus fuel competition. Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms. Sweet Sorghum is an excellent candidate as substrate for microbial oil production, as it possesses high photosynthetic activity yielding high amounts of soluble and insoluble carbohydrates, and does not require high fertilization and irrigation rates.
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High concentrations of dried Sorghum Stalks as a biomass feedstock for single cell oil production by Rhodosporidium toruloides
Biotechnology for Biofuels, 2015Co-Authors: Leonidas Matsakas, Ulrika Rova, Nemailla Bonturi, Everson Alves Miranda, Paul ChristakopoulosAbstract:Background Environmental crisis and concerns for energy security have made the research for renewable fuels that will substitute the usage of fossil fuels an important priority. Biodiesel is a potential substitute for petroleum, but its feasibility is hindered by the utilization of edible vegetable oil as raw material, which is responsible for a large fraction of the production cost and fosters the food versus fuel competition. Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms. Sweet Sorghum is an excellent candidate as substrate for microbial oil production, as it possesses high photosynthetic activity yielding high amounts of soluble and insoluble carbohydrates, and does not require high fertilization and irrigation rates. Results Initially the ability of sweet Sorghum to fully support yeast growth, both as a carbon and nitrogen source was evaluated. It was found that addition of an external nitrogen source had a negative impact on single cell oil (SCO) production yields, which has a positive effect on the process economics. Subsequently the effect of the presence of a distinct saccharification step on SCO was examined. The presence of an enzymatic saccharification step prior to SCO production improved the production of SCO, especially in high solid concentrations. Removal of solids was also investigated and its positive effect on SCO production was also demonstrated. When juice from 20% w/w enzymatically liquefied sweet Sorghum was used as the raw material, SCO production was 13.77 g/L. To the best of our knowledge this is one of the highest SCO titers reported in the literature when renewable raw materials were utilized. Conclusions The use of sweet Sorghum at high solid concentrations as a feedstock for the efficient production of SCO by Rhodosporidium toruloides was demonstrated. Moreover, addition of enzymes not only led to liquefaction of sweet Sorghum and permitted liquid fermentation, but also enhanced lipid production by 85.1% and 15.9% when dried Stalks or stalk juice was used, respectively.
Paul Christakopoulos - One of the best experts on this subject based on the ideXlab platform.
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Direct electricity generation from sweet Sorghum Stalks and anaerobic sludge
Industrial Crops and Products, 2017Co-Authors: Magnus Sjöblom, Leonidas Matsakas, Ulrika Rova, Adolf Krige, Paul ChristakopoulosAbstract:Abstract Dried sweet Sorghum Stalks were valorized as a raw material for electricity generation in a two chamber microbial fuel cell using anaerobic sludge from a biogas plant as inoculum. The maximum voltage obtained on the Sorghum Stalks at an operating temperature of 35 °C was 546 mV with a maximum power- and current density of 131 mW/m2 and 543 mA/m2, respectively. The coulombic efficiency was 2.2%. Polarization data indicated that Ohmic resistances were dominant with an internal resistance of 182 Ω. The total electrical energy per gram of dried Sorghum Stalks was 165 J/g. Enzymatic treatment of the Sorghum Stalks did not improve the total electrical energy obtained. A metabolic study demonstrated that the sugars were quickly fermented to formate, acetate, propionate, lactate and butyrate with acetate and butyrate being the dominant acids during electricity generation.
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high concentrations of dried Sorghum Stalks as a biomass feedstock for single cell oil production by rhodosporidium toruloides
Biotechnology for Biofuels, 2015Co-Authors: Leonidas Matsakas, Ulrika Rova, Nemailla Bonturi, Everson Alves Miranda, Paul ChristakopoulosAbstract:Background Environmental crisis and concerns for energy security have made the research for renewable fuels that will substitute the usage of fossil fuels an important priority. Biodiesel is a potential substitute for petroleum, but its feasibility is hindered by the utilization of edible vegetable oil as raw material, which is responsible for a large fraction of the production cost and fosters the food versus fuel competition. Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms. Sweet Sorghum is an excellent candidate as substrate for microbial oil production, as it possesses high photosynthetic activity yielding high amounts of soluble and insoluble carbohydrates, and does not require high fertilization and irrigation rates.
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High concentrations of dried Sorghum Stalks as a biomass feedstock for single cell oil production by Rhodosporidium toruloides
Biotechnology for Biofuels, 2015Co-Authors: Leonidas Matsakas, Ulrika Rova, Nemailla Bonturi, Everson Alves Miranda, Paul ChristakopoulosAbstract:Background Environmental crisis and concerns for energy security have made the research for renewable fuels that will substitute the usage of fossil fuels an important priority. Biodiesel is a potential substitute for petroleum, but its feasibility is hindered by the utilization of edible vegetable oil as raw material, which is responsible for a large fraction of the production cost and fosters the food versus fuel competition. Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms. Sweet Sorghum is an excellent candidate as substrate for microbial oil production, as it possesses high photosynthetic activity yielding high amounts of soluble and insoluble carbohydrates, and does not require high fertilization and irrigation rates. Results Initially the ability of sweet Sorghum to fully support yeast growth, both as a carbon and nitrogen source was evaluated. It was found that addition of an external nitrogen source had a negative impact on single cell oil (SCO) production yields, which has a positive effect on the process economics. Subsequently the effect of the presence of a distinct saccharification step on SCO was examined. The presence of an enzymatic saccharification step prior to SCO production improved the production of SCO, especially in high solid concentrations. Removal of solids was also investigated and its positive effect on SCO production was also demonstrated. When juice from 20% w/w enzymatically liquefied sweet Sorghum was used as the raw material, SCO production was 13.77 g/L. To the best of our knowledge this is one of the highest SCO titers reported in the literature when renewable raw materials were utilized. Conclusions The use of sweet Sorghum at high solid concentrations as a feedstock for the efficient production of SCO by Rhodosporidium toruloides was demonstrated. Moreover, addition of enzymes not only led to liquefaction of sweet Sorghum and permitted liquid fermentation, but also enhanced lipid production by 85.1% and 15.9% when dried Stalks or stalk juice was used, respectively.
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Production of butyric acid by Clostridium tyrobutyricum (ATCC25755) using sweet Sorghum Stalks and beet molasses
Industrial Crops and Products, 2015Co-Authors: Magnus Sjöblom, Leonidas Matsakas, Paul Christakopoulos, Ulrika RovaAbstract:Enzymatically liquefied sweet Sorghum Stalks and beet molasses were evaluated for butyrate production using Clostridium tyrobutyricum in 1L scale fed-batch fermentations. The hydrolysates used for the fermentations were prepared separately by liquefying the Sorghum Stalks at 50°C, pH 5.0 for 18h, with 30% (w/v) DM content using the enzyme preparation Cellic® CTec2 at an activity of 26.5FPU/gDM. To enhance sucrose consumption, the fermentations were supplemented with invertase at an activity equivalent to 8.3U/gDM. With the hydrolysate as the feedstock, a butyrate concentration of 37.2±0.8g/L, a productivity of 0.86±0.02g/Lh and a yield of 0.39±0.02g/g (p=0.05) consumed sugars were obtained. Finally, a butyrate concentration of 58.8g/L, a productivity of 1.9g/Lh, a butyrate yield of 0.52g/g consumed sugars and a dry cell mass concentration of 15.7g/L were obtained with fed-batch cultivation and a constant feed consisting of 64% Sorghum hydrolysate juice and 36% molasses. Evidence for inducible saccharolytic activity was also proven, as the cellulase activity in the culture supernatant was found more than double during feed with limiting sugar concentrations. The present study clearly demonstrates that combinations of low cost raw materials can be used for efficient butyrate production, also without cell immobilization.
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use of dried sweet Sorghum for the efficient production of lipids by the yeast lipomyces starkeyi cbs 1807
Industrial Crops and Products, 2014Co-Authors: Leonidas Matsakas, Ulrika Rova, Aikateriniaithra Sterioti, Paul ChristakopoulosAbstract:Abstract The ability of the oleaginous yeast Lipomyces starkeyi to efficiently produce lipids when cultivated on saccharified sweet Sorghum Stalks juice was evaluated. Initially the production of lipids using synthetic media mimicking sweet Sorghum Stalks has been studied and optimized concerning the nitrogen source and the C:N ratio. Under optimum conditions (yeast extract as nitrogen source and C:N ratio of 190) the lipid production reached 5.81 g/L with a lipid content of 47.3% (w/w) from a mixture of sucrose, glucose and fructose, mimicking the sugar composition of Sorghum. When cultivated on sweet Sorghum Stalks juice, it was observed that no external nitrogen addition was necessary which could result in substantial decrease of the initial C:N ratio. Moreover a distinct saccharification process prior to yeast cultivation improved the lipid production yield as it resulted in an increase of the C:N ratio. The highest lipid production, which was 6.40 g/L with a lipid content of 29.5% (w/w), was obtained when juice from saccharified sweet Sorghum Stalks at an initial Sorghum content of 12% (w/w) was used as feedstock.
Lei Zhang - One of the best experts on this subject based on the ideXlab platform.
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RNA-Seq-based transcriptomic analysis of Saccharomyces cerevisiae during solid-state fermentation of crushed sweet Sorghum Stalks
Process Biochemistry, 2018Co-Authors: Lei ZhangAbstract:Abstract Bioethanol production based on solid-state fermentation (SSF) of sweet Sorghum Stalks has been demonstrated to have great potential due to the its low pollution and low cost. A novel S. cerevisiae strain TSH3 exhibited better SSF performance compared with BY4743 during SSF of sweet Sorghum Stalks. High-quality total RNA of S. cerevisiae was extracted from SSF mixture and the global gene expression profiles during SSF were studied using RNA-Seq. Compared with BY4743, TSH3’s genes related to ribosome biogenesis, amino acid and coenzyme metabolism during early fermentation stage, secondary metabolite biosynthesis, metabolism in diverse environment during middle fermentation stage, and lipid metabolism during late fermentation stage were up-regulated; while the genes involved in fatty acid metabolism and peroxisome during early fermentation stage, ribosome biogenesis during middle fermentation stage, and mitotic cell cycle during late fermentation stage were down-regulated. Further dynamic analysis of TSH3’s transcriptome reveals its three different metabolic stages: 1) ribosome biogenesis and respiration-fermentation transition; 2) biosynthesis of secondary metabolites and stress resistance; 3) plasma membrane related metabolism for stress resistance. These findings provided insight into the S. cerevisiae transcriptome during SSF of sweet Sorghum Stalks and suggest that TSH3 would be an ideal candidate for SSF-based bioethanol production.
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a novel combined ethanol and power model of microgrid driven by sweet Sorghum Stalks using assf
Energy Procedia, 2016Co-Authors: Lei ZhangAbstract:Abstract In this study, we proposed a novel combined ethanol and power (CEP) model of microgrid driven by sweet Sorghum ethanol using advanced solid-state fermentation (ASSF), during which a great deal of solid vinasse will be generated. In the model, a 10,000-tonne scale ethanol plant with a 2.5 MW biopower plant driving by ASSF technology can support ∼4,000 households of remote area for one-year regular electricity use, denoting that economically viable ethanol production is able to provide a steady biomass supply for combined heat and power generation. Accordingly, the novel CEP microgrid model exhibits much more robust and stable traits compared with conventional microgrids.
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Impact of lignin removal on the enzymatic hydrolysis of fermented sweet Sorghum bagasse.
Applied Energy, 2015Co-Authors: Zhipei Yan, Ting Cui, Yan Jiang, Guangtao Cong, Sandra Chang, Lei ZhangAbstract:The complete utilization of sweet Sorghum Stalks including the fermentable sugars and the lignocellulosic faction is necessary to decrease the bioethanol production cost. Moreover, bioethanol yields from lignocellulosic resources depend on the saccharification efficiency of cellulose. Lignin has been considered as an important factor influencing enzymatic hydrolysis of lignocellulose. In this study, the impact of lignin removal on enzymatic hydrolysis was investigated using fermented sweet Sorghum bagasse (FSSB) delignified by NaOH or Ca(OH)2 pretreatments. For NaOH pretreated samples, a positive correlation between cellulose conversion rate and lignin removal was found when the lignin removal was from 8.96% to 65.61%. Further delignification of FSSB did not increase the efficiency of enzymatic hydrolysis. For Ca(OH)2 pretreatment, there was no obvious correlation between lignin removal and cellulose conversion rate. More interestingly, the cellulose conversion rate of FSSB pretreated with Ca(OH)2 was significantly higher than that of FSSB pretreated with NaOH when the same amount of lignin was removed. The surface lignin coverage of FSSB pretreated with 10% NaOH was 1.52 times higher than that of FSSB pretreated with Ca(OH)2. These results demonstrated that the impact of lignin removal on enzymatic hydrolysis of FSSB pretreated with NaOH and Ca(OH)2 was different. The lignin removal was the main factor influencing the enzymatic hydrolysis of FSSB pretreated with NaOH, while Ca(OH)2 was more capable of removing surface lignin when the lignin content of the samples was similar.
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The application of near infrared spectroscopy in process monitoring of solid-state fermentation of sweet Sorghum Stalks
Journal of Near Infrared Spectroscopy, 2015Co-Authors: Fan Guifang, Yan Jiang, Sandra Chang, Lei Zhang, Gang ZhaoAbstract:Multiple samples (117) of sweet Sorghum stalk particles were analysed qualitatively and quantitatively during solid-state fermentation using near infrared spectroscopy and chemometrics methods. The study indicated that the samples could be identified to the lag phase, exponential phase or stationary phase of the ethanol fermentation process by discriminant analysis of a principal component analysis (PCA) model. The first principal component score of PCA could be used to predict the extent of reaction, regardless of the value of parameters, such as pH value and sugar, ethanol and water content. The r2 values of multivariate regression models for mass fractions of sugar, alcohol and water, and pH were 0.93, 0.94, 0.87 and 0.95, respectively. The root mean standard errors of prediction for mass fractions of sugar, alcohol and water, and pH were 0.013, 0.006, 0.008 w w−1 and 0.15, respectively. The partial least squares regression of the value of pH had the best fit of the four parameters. Near infrared spectroscopy could be used successfully in process monitoring of solid-state fermentation of sweet Sorghum Stalks.
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A novel wild-type Saccharomyces cerevisiae strain TSH1 in scaling-up of solid-state fermentation of ethanol from sweet Sorghum Stalks.
PloS one, 2014Co-Authors: Jianbin Yan, Lei Zhang, Quanzhou Feng, Sandra P. ChangAbstract:The rising demand for bioethanol, the most common alternative to petroleum-derived fuel used worldwide, has encouraged a feedstock shift to non-food crops to reduce the competition for resources between food and energy production. Sweet Sorghum has become one of the most promising non-food energy crops because of its high output and strong adaptive ability. However, the means by which sweet Sorghum Stalks can be cost-effectively utilized for ethanol fermentation in large-scale industrial production and commercialization remains unclear. In this study, we identified a novel Saccharomyces cerevisiae strain, TSH1, from the soil in which sweet Sorghum Stalks were stored. This strain exhibited excellent ethanol fermentative capacity and ability to withstand stressful solid-state fermentation conditions. Furthermore, we gradually scaled up from a 500-mL flask to a 127-m3 rotary-drum fermenter and eventually constructed a 550-m3 rotary-drum fermentation system to establish an efficient industrial fermentation platform based on TSH1. The batch fermentations were completed in less than 20 hours, with up to 96 tons of crushed sweet Sorghum Stalks in the 550-m3 fermenter reaching 88% of relative theoretical ethanol yield (RTEY). These results collectively demonstrate that ethanol solid-state fermentation technology can be a highly efficient and low-cost solution for utilizing sweet Sorghum, providing a feasible and economical means of developing non-food bioethanol.
Lakkana Laopaiboon - One of the best experts on this subject based on the ideXlab platform.
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Kinetic models for batch and continuous ethanol fermentation from sweet Sorghum juice by yeast immobilized on sweet Sorghum Stalks
Journal of the Taiwan Institute of Chemical Engineers, 2016Co-Authors: Pongthep Ariyajaroenwong, Pattana Laopaiboon, Apilak Salakkam, Penjit Srinophakun, Lakkana LaopaiboonAbstract:Kinetic models for batch and continuous ethanol fermentation from sweet Sorghum juice by Saccharomyces cerevisiae NP 01 immobilized on unpeeled sweet Sorghum stalk pieces were developed. The models accounted for substrate limitation, substrate inhibition, ethanol inhibition and cell death. Batch ethanol fermentations were done from juice containing various initial sugar concentrations (120–280 g/L). The estimated values of the maximum specific growth rate (μmax) and Monod constant (Ks) were found to be 0.313 h−1 and 47.51 g/L, respectively, using a Lineweaver–Burk plot. These data were used to develop models for batch and continuous ethanol fermentation. For the batch fermentation, it was found that the models could be used to satisfactorily fit the experimental data for initial sugar concentrations ranging from 130 to 225 g/L. However, for the continuous fermentation, only the data for substrate consumption and ethanol production were well fitted by the developed models.
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capability of sweet Sorghum Stalks as supporting materials for yeast immobilization to produce ethanol under various fermentation processes
Journal of The Taiwan Institute of Chemical Engineers, 2015Co-Authors: Pongthep Ariyajaroenwong, Pattana Laopaiboon, Lakkana LaopaiboonAbstract:Abstract Unpeeled sweet Sorghum stalk (SSS) pieces sizing 6- to 20-mm diameter and 6-mm thick were used as carriers for Saccharomyces cerevisiae NP 01 immobilization to produce ethanol. The diluted sweet Sorghum juice containing 100 g/l of total sugar without nutrient supplementation was a suitable medium for yeast cell immobilization, and 18 h incubation time was sufficient for the immobilization process. In repeated-batch ethanol fermentation from sweet Sorghum juice (240 g/l of total sugar) at 30 °C, the average ethanol concentration (P), productivity (QP) and yield (YP/S) by the immobilized yeast cells were 93.4 g/l, 1.30 g/l h and 0.47 g/g, respectively. When the continuous system was operated in a double-tubular packed-bed bioreactor with 50% bed height, the average P, QP and YP/S were comparable to those of the repeated-batch fermentation. Supplementation the juice with 6 g/l of yeast extract resulted in significant increases in P, QP and YP/S to 105.7 g/l, 2.43 g/l h and 0.48 g/g, respectively at the dilution rate of 0.023/h. These results demonstrated that the unpeeled SSS pieces were successfully used as low-cost carriers for yeast cell immobilization to produce ethanol under both repeated-batch and continuous systems.
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Repeated-Batch Ethanol Production from Sweet Sorghum Juice by Saccharomyces cerevisiae Immobilized on Sweet Sorghum Stalks
Energies, 2012Co-Authors: Pongthep Ariyajaroenwong, Pattana Laopaiboon, Prasit Jaisil, Lakkana LaopaiboonAbstract:Sweet Sorghum Stalks were used as a low cost carrier for immobilization of Saccharomyces cerevisiae NP 01 to produce ethanol from sweet Sorghum juice. The effects on ethanol production of carrier size (6 × 6 × 6 to 20 × 20 × 20 mm3) and initial cell concentrations (5 × 107 to 2 × 108 cells mL−1) for cell immobilization were investigated. The ethanol production medium was the juice containing 230 g L−1 of total sugar without nutrient supplementation. The fermentations were carried out under static conditions in 500-mL air-locked Erlenmeyer flasks at 30 °C. The results showed that the optimum size of Sorghum stalk pieces for repeated-batch ethanol production was 6 × 6 × 6 mm3, while the optimum initial cell concentration for the immobilization was 1.0 × 108 cells mL−1. The immobilized yeast under these conditions could be used for at least eight successive batches without any losses of ethanol production efficiencies. The average ethanol concentration, productivity and yield of the eight successive batches were 99.28 ± 3.53 g L−1, 1.36 ± 0.05 g L−1 h−1 and 0.47 ± 0.03 g g−1, respectively.