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Christopher J. Chuck - One of the best experts on this subject based on the ideXlab platform.

  • variation among Metschnikowia pulcherrima isolates for genetic modification and homologous recombination
    Microorganisms, 2021
    Co-Authors: Mauro Morenobeltran, Christopher J. Chuck, Deborah Gorelloyd, Daniel A Henk
    Abstract:

    Metschnikowia pulcherrima is a non-conventional yeast with the potential to be used in biotechnological processes, especially involving low-cost feedstock exploitation. However, there are a lack of tools for researching it at a molecular level and for producing genetically modified strains. We tested the amenability to genetic modification of ten different strains, establishing a transformation protocol based on LiAc/PEG that allows us to introduce heterologous DNA. Non-homologous integration was broadly successful and homologous recombination was successful in two strains. Chemical inhibition of non-homologous end joining recombination had a modest effect on the improvement of homologous recombination rates. Removal of selective markers via flippase recombinase was successful across integrated loci except for those targeted to the native URA3 locus, suggesting that the genome sequence or structure alters the efficacy of this system.

  • semi continuous pilot scale microbial oil production with Metschnikowia pulcherrima on starch hydrolysate
    Biotechnology for Biofuels, 2020
    Co-Authors: Felix Abeln, Mauro Morenobeltran, Daniel A Henk, Robert H Hicks, Hadiza Auta, Luca Longanesi, Christopher J. Chuck
    Abstract:

    Heterotrophic microbial oils are potentially a more sustainable alternative to vegetable or fossil oils for food and fuel applications. However, as almost all work in the area is conducted on the laboratory scale, such studies carry limited industrial relevance and do not give a clear indication of what is required to produce an actual industrial process. Metschnikowia pulcherrima is a non-pathogenic industrially promising oleaginous yeast which exhibits numerous advantages for cost-effective lipid production, including a wide substrate uptake, antimicrobial activity and fermentation inhibitor tolerance. In this study, M. pulcherrima was fermented in stirred tank reactors of up to 350 L with 250-L working volume in both batch and semi-continuous operation to highlight the potential industrial relevance. Due to being food-grade, suitable for handling at scale and to demonstrate the oligosaccharide uptake capacity of M. pulcherrima, enzyme-hydrolysed starch in the form of glucose syrup was selected as fermentation feedstock. In batch fermentations on the 2-L scale, a lipid concentration of 14.6 g L−1 and productivity of 0.11 g L−1 h−1 were achieved, which was confirmed at 50 L (15.8 g L−1; 0.10 g L−1 h−1). The maximum lipid production rate was 0.33 g L−1 h−1 (daily average), but the substrate uptake rate decreased with oligosaccharide chain length. To produce 1 kg of dry yeast biomass containing up to 43% (w/w) lipids, 5.2 kg of the glucose syrup was required, with a lipid yield of up to 0.21 g g−1 consumed saccharides. In semi-continuous operation, for the first time, an oleaginous yeast was cultured for over 2 months with a relatively stable lipid production rate (around 0.08 g L−1 h−1) and fatty acid profile (degree of fatty acid saturation around 27.6% w/w), and without contamination. On the 250-L scale, comparable results were observed, culminating in the generation of nearly 10 kg lipids with a lipid productivity of 0.10 g L−1 h−1. The results establish the importance of M. pulcherrima for industrial biotechnology and its suitability to commercially produce a food-grade oil. Further improvements in the productivity are required to make M. pulcherrima lipid production industrial reality, particularly when longer-chain saccharides are involved.

  • the role of temperature ph and nutrition in process development of the unique oleaginous yeast Metschnikowia pulcherrima
    Journal of Chemical Technology & Biotechnology, 2019
    Co-Authors: Felix Abeln, Christopher J. Chuck
    Abstract:

    BACKGROUND: Lipids produced from oleaginous yeasts are a promising alternative to terrestrial oils. Despite promising cellular yields of lipid however, an industrial process remains elusive. One key processing bottleneck is the need to provide nutrient‐rich conditions for cellular growth and then extended nutrient‐depleted conditions for lipid accumulation. Surprisingly, investigations detailing process development, particularly with a focus on kinetics, are rare in this field. RESULTS: In this investigation we report on the unique oleaginous yeast Metschnikowia pulcherrima, where lipid accumulation ≥ 29.8% (w/w) was achieved without apparent nutrient limitation. The process was developed in stirred tank reactors through determining the influence of temperature, pH and nutrition on lipid production. A temperature of up to 25 °C and initial pH 5 could be applied to enhance initial reaction kinetics. Through the increased supply of yeast extract of up to 5% (w/w) of glucose, a maximum lipid production rate of 0.60 g L⁻¹ h⁻¹ (4 h‐average), productivity of 0.29 g L⁻¹ h⁻¹, and yield of 0.17 g g⁻¹ glucose were achieved – the highest yet recorded with this yeast. Suitable to combat the excessive secretion of polyols of up to 0.11 g g⁻¹ glucose was an excess nutrient supply as well as a low cultivation temperature of 15 °C and moderate pH 5. CONCLUSIONS: This study demonstrates that the lack of a starvation stage, coupled with effective process development is required for oleaginous yeasts to achieve the yields and productivities required for commercial lipid production. © 2019 Society of Chemical Industry

  • achieving a high density oleaginous yeast culture comparison of four processing strategies using Metschnikowia pulcherrima
    Biotechnology and Bioengineering, 2019
    Co-Authors: Felix Abeln, Christopher J. Chuck
    Abstract:

    Microbial lipids have the potential to displace terrestrial oils for fuel, value chemical, and food production, curbing the growth in tropical oil plantations and helping to reduce deforestation. However, commercialization remains elusive partly due to the lack of suitably robust organisms and their low lipid productivity. Extremely high cell densities in oleaginous cultures are needed to increase reaction rates, reduce reactor volume, and facilitate downstream processing. In this investigation, the oleaginous yeast Metschnikowia pulcherrima, a known antimicrobial producer, was cultured using four different processing strategies to achieve high cell densities and gain suitable lipid productivity. In batch mode, the yeast demonstrated lipid contents more than 40% (w/w) under high osmotic pressure. In fed-batch mode, however, high-lipid titers were prevented through inhibition above 70.0 g L-1 yeast biomass. Highly promising were a semi-continuous and continuous mode with cell recycle where cell densities of up to 122.6 g L-1 and maximum lipid production rates of 0.37 g L-1  h-1 (daily average), a nearly two-fold increase from the batch, were achieved. The findings demonstrate the importance of considering multiple fermentation modes to achieve high-density oleaginous yeast cultures generally and indicate the limitations of processing these organisms under the extreme conditions necessary for economic lipid production.

  • lipid production through the single step microwave hydrolysis of macroalgae using the oleaginous yeast Metschnikowia pulcherrima
    Algal Research-Biomass Biofuels and Bioproducts, 2019
    Co-Authors: Felix Abeln, Daniel A Henk, Jiajun Fan, Vitaliy L Budarin, Hannah Briers, Sophie Parsons, Michael J Allen, James H Clark, Christopher J. Chuck
    Abstract:

    Abstract Macroalgae (seaweeds) represent an emerging resource for food and the production of commodity and specialty chemicals. In this study, a single-step microwave process was used to depolymerise a range of macroalgae native to the United Kingdom, producing a growth medium suitable for microbial fermentation. The medium contained a range of mono- and polysaccharides as well as macro- and micronutrients that could be metabolised by the oleaginous yeast Metschnikowia pulcherrima. Among twelve macroalgae species, the brown seaweeds exhibited the highest fermentation potential, especially the kelp Saccharina latissima. Applying a portfolio of ten native M. pulcherrima strains, yeast growth kinetics, as well as production of lipids and 2-phenylethanol were examined, with productivity and growth rate being strain dependent. On the 2 L scale, 6.9 g L−1 yeast biomass – a yield of 0.14 g g−1 with respect to the supplied macroalgae – containing 37.2% (w/w) lipid was achieved through utilisation of the proteins, mono- and polysaccharides from S. latissima, with no additional enzymes. In addition, the yeast degraded a range of fermentation inhibitors released upon microwave processing at high temperatures and long holding times. As macroalgae can be cultured to food grade, this system offers a novel, potentially low-cost route to edible microbial oils as well as a renewable feedstock for oleochemicals.

Benoit Divol - One of the best experts on this subject based on the ideXlab platform.

  • the expression secretion and activity of the aspartic protease mpapr1 in Metschnikowia pulcherrima iwbt y1123
    Journal of Industrial Microbiology & Biotechnology, 2019
    Co-Authors: C Snyman, Louwrens Wiid Theron, Benoit Divol
    Abstract:

    Protease-secreting yeasts have broad biotechnological potential for application to various industrial processes, including winemaking. However, this activity is influenced by the yeast response to environmental factors such as nitrogen and protein sources, as are found in grape juice. In this study, the wine-relevant yeast Metschnikowia pulcherrima IWBT Y1123, with known protease-secreting ability, was subjected to different nitrogen-containing compounds to monitor their impact on protease secretion and activity. Protease activity increased above basal levels for haemoglobin-containing treatments, indicating an inductive influence of proteins. On the other hand, treatments containing both haemoglobin and assimilable nitrogen sources led to a delayed increase in protease activity and protein degradation, suggesting a nitrogen catabolite repression mechanism at work. Protease activity and expression were furthermore evaluated in grape juice, which revealed increased expression and activity levels over time as promising results for further investigations into the impact of this yeast on wine properties.

  • characterisation of the enzymatic properties of mpapr1 an aspartic protease secreted by the wine yeast Metschnikowia pulcherrima
    Journal of the Science of Food and Agriculture, 2017
    Co-Authors: Louwrens Wiid Theron, Marina Bely, Benoit Divol
    Abstract:

    MpAPr1, encoding an acid protease from the wine yeast Metschnikowia pulcherrima IWBT Y1123, was previously isolated and shown to display potential activity against casein and grape proteins. However, its characterisation remained partial.; Results: MpAPr1 was cloned into the pGAPZαA vector and transformed into Komagataella pastoris X33 for heterologous expression. After verification of activity, the enzyme properties were characterised. Protease activity within the concentrated supernatant was retained over a pH range of 3.0 to 5.0 and between 10 °C and 50 °C. Optimal conditions for protease activity were found at 40 °C and pH 4.5. Activity was mostly unaffected by the presence of metal ions with the exception of Cu2+ and Ni2+ . Furthermore, proteolytic activity was retained in the presence of sugar and ethanol. pH and temperature conditions for MpAPr1 expression in K. pastoris were optimised. Purification was achieved by means of cation exchange chromatography and kinetic parameters (Km and Vmax ) were determined. MpAPr1 activity against grape proteins was confirmed, but the extent of the degradation was dependent on the nature of these proteins and the environmental conditions.; Conclusion: Overall, the results suggest that MpAPr1 could be applied in food biotechnology processes such as winemaking. © 2017 Society of Chemical Industry.; © 2017 Society of Chemical Industry.

  • identification and partial characterization of extracellular aspartic protease genes from Metschnikowia pulcherrima iwbt y1123 and candida apicola iwbt y1384
    Applied and Environmental Microbiology, 2012
    Co-Authors: Vernita J Reid, Louwrens Wiid Theron, Maret Du Toit, Benoit Divol
    Abstract:

    The extracellular acid proteases of non-Saccharomyces wine yeasts may fulfill a number of roles in winemaking, which include increasing the available nitrogen sources for the growth of fermentative microbes, affecting the aroma profile of the wine, and potentially reducing protein haze formation. These proteases, however, remain poorly characterized, especially at genetic level. In this study, two extracellular aspartic protease-encoding genes were identified and sequenced, from two yeast species of enological origin: one gene from Metschnikowia pulcherrima IWBT Y1123, named MpAPr1, and the other gene from Candida apicola IWBT Y1384, named CaAPr1. In silico analysis of these two genes revealed a number of features peculiar to aspartic protease genes, and both the MpAPr1 and CaAPr1 putative proteins showed homology to proteases of yeast genera. Heterologous expression of MpAPr1 in Saccharomyces cerevisiae YHUM272 confirmed that it encodes an aspartic protease. MpAPr1 production, which was shown to be constitutive, and secretion were confirmed in the presence of bovine serum albumin (BSA), casein, and grape juice proteins. The MpAPr1 gene was found to be present in 12 other M. pulcherrima strains; however, plate assays revealed that the intensity of protease activity was strain dependent and unrelated to the gene sequence.

D Spadaro - One of the best experts on this subject based on the ideXlab platform.

  • potential of two Metschnikowia pulcherrima yeast strains for in vitro biodegradation of patulin
    Journal of Food Protection, 2011
    Co-Authors: K R N Reddy, D Spadaro, Maria Lodovica Gullino, Angelo Garibaldi
    Abstract:

    Patulin contamination of apple and other fruit-based foods and beverages is an important food safety issue, as consumption of these commodities throughout the world is great. Studies are therefore necessary to reduce patulin levels to acceptable limits or undetectable levels to minimize toxicity. This study was undertaken to investigate the efficacy of two Metschnikowia pulcherrima strains (MACH1 and GS9) on biodegradation of patulin under in vitro conditions. These yeast strains were tested for their abilities to degrade patulin in liquid medium amended with 5, 7.5, 10, and 15 μg/ml patulin and a yeast cell concentration of 1 × 10(8) cells per ml at 25°C. Of the two strains tested, MACH1 completely (100%) reduced patulin levels within 48 h, and GS9 within 72 h, at all concentrations of patulin. MACH1 effectively degraded the patulin within 24 h by 83 to 87.4%, and GS9 by 73 to 75.6% at 48 h, regardless of concentration. Patulin was not detected in yeast cell walls. This indicates that yeast cell walls did not absorb patulin, and that they completely degraded the toxin. Patulin had no influence on yeast cell concentration during growth. Therefore, these yeast strains could potentially be used for the reduction of patulin in naturally contaminated fruit juices. To our knowledge, this is the first report regarding the potential of M. pulcherrima strains for patulin biodegradation.

  • effect of culture media and ph on the biomass production and biocontrol efficacy of a Metschnikowia pulcherrima strain to be used as a biofungicide for postharvest disease control
    Canadian Journal of Microbiology, 2010
    Co-Authors: D Spadaro, Annalisa Ciavorella, Zhang Dianpeng, A Garibaldi, M L Gullino
    Abstract:

    Few strains of Metschnikowia pulcherrima (Pitt) M.W. Miller are under development for control of postharvest pathogens on fruit. A substrate was developed to optimize the biomass production of M. p...

  • effect of culture media and ph on the biomass production and biocontrol efficacy of a Metschnikowia pulcherrima strain to be used as a biofungicide for postharvest disease control
    Canadian Journal of Microbiology, 2010
    Co-Authors: D Spadaro, Annalisa Ciavorella, Zhang Dianpeng, A Garibaldi, M L Gullino
    Abstract:

    Few strains of Metschnikowia pulcherrima (Pitt) M.W. Miller are under development for control of postharvest pathogens on fruit. A substrate was developed to optimize the biomass production of M. pulcherrima strain BIO126. Different complex nutrient sources, with or without pH control, were tested. Growth in yeast extract provided at concentrations ≥30 g·L–1 yielded the highest biomass. The addition of two carbon sources, d-mannitol and l-sorbose, at 5 g·L–1 each, significantly improved yeast growth. The greatest amount of yeast growth occurred when pH values of the medium ranged from 5.0 to 7.5. A combination of yeast extract, d-mannitol, and l-sorbose (YEMS), probably with diauxic utilization, showed a synergistic effect, widening the exponential phase (maximum specific growth rate of 0.45 h–1) and increasing the final cell number (1.5 × 109 cells·mL–1) and dry biomass (6.0 g·L–1) in well-controlled batch fermentation. In efficacy trials on ‘Golden Delicious’ apples, M. pulcherrima grown in YEMS effecti...

  • use of aflp for differentiation of Metschnikowia pulcherrima strains for postharvest disease biological control
    Microbiological Research, 2008
    Co-Authors: D Spadaro, A Garibaldi, Wilma Sabetta, Alberto Acquadro, Ezio Portis, Maria Lodovica Gullino
    Abstract:

    Metschnikowia pulcherrima occurs naturally on fruits, buds and floral parts of apple trees. Some strains are effective as biocontrol agents against postharvest decay of apples and other fruits. The usefulness of the amplified fragment length polymorphism (AFLP) technique was evaluated for the genetic analysis of 26 strains of M. pulcherrima, isolated from different sources in different geographical regions. With six AFLP primer pairs, 729 polymorphic bands were scored. The technique showed a high discriminatory power. Genetic relationships between strains were also estimated using AFLP. All the isolates from the carposphere of apple, previously tested as biocontrol agents, were grouped in a single cluster with a high bootstrap value (97), indicating robustness and reproducibility. AFLP patterns could clearly distinguish the different strains and research is in progress to use some putative specific bands for single tag sequence (STS) conversion to develop isolate-specific markers.

  • Metschnikowia pulcherrima strain mach1 outcompetes botrytis cinerea alternaria alternata and penicillium expansum in apples through iron depletion
    Postharvest Biology and Technology, 2008
    Co-Authors: D Saravanakumar, Angelo Garibaldi, Annalisa Ciavorella, D Spadaro, Lodovica M Gullino
    Abstract:

    Abstract A new strain of Metschnikowia pulcherrima (MACH1) was studied for its efficacy as a biocontrol agent against Botrytis cinerea, Penicillium expansum and Alternaria alternata on apples stored for 8 months at 1 °C. The results of two semi-commercial trials demonstrated the efficacy of the biocontrol strain MACH1. In order to understand the mechanism of action involved, the yeast strain was investigated for its competitive ability for iron against postharvest pathogens of apple. M. pulcherrima strain MACH1 was cultivated on PDA with different concentrations of iron (supplemented as FeCl3) against A. alternata and B. cinerea. The yeast strain MACH1 produced a wider pigmented inhibition zone against both pathogens in low iron amendments while less inhibition was measured with increased iron concentrations. At the coloured inhibition zone, B. cinerea and A. alternata conidia did not germinate and mycelial degeneration was observed. In addition, a high reduction in infection by both pathogens was recorded in apples treated with M. pulcherrima strain MACH1 supplemented with low iron amendments compared to higher iron concentrations. The same experiments were carried out in vivo and in vitro against P. expansum. M. pulcherrima strain MACH1 amended with low iron concentration (5 μg mL−1 FeCl3), showing modest lesion diameter reduction and no effect on P. expansum under increased iron and without iron amendments. This study illustrated that iron depletion by the yeast strain MACH1 under low iron conditions could reduce the growth of some postharvest pathogens in vitro and in vivo. Although, iron depletion seems to be a primary mode of action against the postharvest pathogens studied, other mechanisms of action cannot be excluded in the biocontrol employed by M. pulcherrima strain MACH1.

Angelo Garibaldi - One of the best experts on this subject based on the ideXlab platform.

  • potential of two Metschnikowia pulcherrima yeast strains for in vitro biodegradation of patulin
    Journal of Food Protection, 2011
    Co-Authors: K R N Reddy, D Spadaro, Maria Lodovica Gullino, Angelo Garibaldi
    Abstract:

    Patulin contamination of apple and other fruit-based foods and beverages is an important food safety issue, as consumption of these commodities throughout the world is great. Studies are therefore necessary to reduce patulin levels to acceptable limits or undetectable levels to minimize toxicity. This study was undertaken to investigate the efficacy of two Metschnikowia pulcherrima strains (MACH1 and GS9) on biodegradation of patulin under in vitro conditions. These yeast strains were tested for their abilities to degrade patulin in liquid medium amended with 5, 7.5, 10, and 15 μg/ml patulin and a yeast cell concentration of 1 × 10(8) cells per ml at 25°C. Of the two strains tested, MACH1 completely (100%) reduced patulin levels within 48 h, and GS9 within 72 h, at all concentrations of patulin. MACH1 effectively degraded the patulin within 24 h by 83 to 87.4%, and GS9 by 73 to 75.6% at 48 h, regardless of concentration. Patulin was not detected in yeast cell walls. This indicates that yeast cell walls did not absorb patulin, and that they completely degraded the toxin. Patulin had no influence on yeast cell concentration during growth. Therefore, these yeast strains could potentially be used for the reduction of patulin in naturally contaminated fruit juices. To our knowledge, this is the first report regarding the potential of M. pulcherrima strains for patulin biodegradation.

  • effect of culture age protectants and initial cell concentration on viability of freeze dried cells of Metschnikowia pulcherrima
    Canadian Journal of Microbiology, 2010
    Co-Authors: Davide Spadaro, Angelo Garibaldi, Annalisa Ciavorella, J G Lopezreyes, Maria Lodovica Gullino
    Abstract:

    The effect of freeze-drying using different lyoprotectants at different concentrations on the viability and biocontrol efficacy of Metschnikowia pulcherrima was evaluated. The effects of initial yeast cell concentration and culture age on viability were also considered. Yeast cells grown for 36 h were more resistant to freeze-drying than were 48 h cells. An initial concentration of 108 cells·mL–1 favoured the highest survival after freeze-drying. When maltose (25%, m/v) was used as protectant, a high cell viability was obtained (64.2%). Cells maintained a high viability after 6 months of storage at 4 °C. The biocontrol efficacy of freeze-dried cells was similar to the activity of fresh cells on ‘Gala’ apples and was slightly lower on ‘Golden Delicious’ apples. After optimizing freeze-drying conditions, the viability of M. pulcherrima cells was similar to that obtained in other studies. The results constitute a first step towards the commercial development of M. pulcherrima as a biocontrol agent.

  • effect of culture age protectants and initial cell concentration on viability of freeze dried cells of Metschnikowia pulcherrima
    Canadian Journal of Microbiology, 2010
    Co-Authors: Davide Spadaro, Angelo Garibaldi, Annalisa Ciavorella, J G Lopezreyes, Maria Lodovica Gullino
    Abstract:

    The effect of freeze-drying using different lyoprotectants at different concentrations on the viability and biocontrol efficacy of Metschnikowia pulcherrima was evaluated. The effects of initial ye...

  • Detection of enzymatic activity and partial sequence of a chitinase gene in Metschnikowia pulcherrima strain MACH1 used as post-harvest biocontrol agent
    European Journal of Plant Pathology, 2009
    Co-Authors: Duraisamy Saravanakumar, Angelo Garibaldi, Davide Spadaro, M. Lodovica Gullino
    Abstract:

    Two antagonistic yeast strains Metschnikowia pulcherrima MACH1 and Rhodotorula sp. PW34 were tested for their efficacy against Botrytis cinerea in vitro and in vivo on apples. Metschnikowia pulcherrima strain MACH1 showed higher inhibition of B. cinerea compared to the strain PW34 in vitro on potato dextrose broth. Further, yeast strain MACH1 showed higher efficacy in reducing grey mould on apples compared to PW34 and the untreated control. In addition, partially purified extracellular proteins from strain MACH1 showed an inhibition to B. cinerea in vitro. The antagonistic yeast strains were tested for their efficacy to produce chitinases in different liquid media, including apple juice, amended with or without cell wall preparations (CWP) of B. cinerea . The study showed a higher production of chitinases from M. pulcherrima strain MACH1 when compared to PW34. Interestingly, the strain MACH1 secreted higher chitinases in the presence of cell wall fractions of B. cinerea . For this reason, the chitinase gene of strain MACH1 was amplified using PCR reactions and the nucleotide sequence data showed high homology to chitinases of other yeast strains. The results of the current study show that M. pulcherrima strain MACH1 has the ability to secrete chitinases in different liquid media including apple juice, and the enzyme could be involved in the post-harvest biological control of B. cinerea .

  • Metschnikowia pulcherrima strain mach1 outcompetes botrytis cinerea alternaria alternata and penicillium expansum in apples through iron depletion
    Postharvest Biology and Technology, 2008
    Co-Authors: D Saravanakumar, Angelo Garibaldi, Annalisa Ciavorella, D Spadaro, Lodovica M Gullino
    Abstract:

    Abstract A new strain of Metschnikowia pulcherrima (MACH1) was studied for its efficacy as a biocontrol agent against Botrytis cinerea, Penicillium expansum and Alternaria alternata on apples stored for 8 months at 1 °C. The results of two semi-commercial trials demonstrated the efficacy of the biocontrol strain MACH1. In order to understand the mechanism of action involved, the yeast strain was investigated for its competitive ability for iron against postharvest pathogens of apple. M. pulcherrima strain MACH1 was cultivated on PDA with different concentrations of iron (supplemented as FeCl3) against A. alternata and B. cinerea. The yeast strain MACH1 produced a wider pigmented inhibition zone against both pathogens in low iron amendments while less inhibition was measured with increased iron concentrations. At the coloured inhibition zone, B. cinerea and A. alternata conidia did not germinate and mycelial degeneration was observed. In addition, a high reduction in infection by both pathogens was recorded in apples treated with M. pulcherrima strain MACH1 supplemented with low iron amendments compared to higher iron concentrations. The same experiments were carried out in vivo and in vitro against P. expansum. M. pulcherrima strain MACH1 amended with low iron concentration (5 μg mL−1 FeCl3), showing modest lesion diameter reduction and no effect on P. expansum under increased iron and without iron amendments. This study illustrated that iron depletion by the yeast strain MACH1 under low iron conditions could reduce the growth of some postharvest pathogens in vitro and in vivo. Although, iron depletion seems to be a primary mode of action against the postharvest pathogens studied, other mechanisms of action cannot be excluded in the biocontrol employed by M. pulcherrima strain MACH1.

Felix Abeln - One of the best experts on this subject based on the ideXlab platform.

  • semi continuous pilot scale microbial oil production with Metschnikowia pulcherrima on starch hydrolysate
    Biotechnology for Biofuels, 2020
    Co-Authors: Felix Abeln, Mauro Morenobeltran, Daniel A Henk, Robert H Hicks, Hadiza Auta, Luca Longanesi, Christopher J. Chuck
    Abstract:

    Heterotrophic microbial oils are potentially a more sustainable alternative to vegetable or fossil oils for food and fuel applications. However, as almost all work in the area is conducted on the laboratory scale, such studies carry limited industrial relevance and do not give a clear indication of what is required to produce an actual industrial process. Metschnikowia pulcherrima is a non-pathogenic industrially promising oleaginous yeast which exhibits numerous advantages for cost-effective lipid production, including a wide substrate uptake, antimicrobial activity and fermentation inhibitor tolerance. In this study, M. pulcherrima was fermented in stirred tank reactors of up to 350 L with 250-L working volume in both batch and semi-continuous operation to highlight the potential industrial relevance. Due to being food-grade, suitable for handling at scale and to demonstrate the oligosaccharide uptake capacity of M. pulcherrima, enzyme-hydrolysed starch in the form of glucose syrup was selected as fermentation feedstock. In batch fermentations on the 2-L scale, a lipid concentration of 14.6 g L−1 and productivity of 0.11 g L−1 h−1 were achieved, which was confirmed at 50 L (15.8 g L−1; 0.10 g L−1 h−1). The maximum lipid production rate was 0.33 g L−1 h−1 (daily average), but the substrate uptake rate decreased with oligosaccharide chain length. To produce 1 kg of dry yeast biomass containing up to 43% (w/w) lipids, 5.2 kg of the glucose syrup was required, with a lipid yield of up to 0.21 g g−1 consumed saccharides. In semi-continuous operation, for the first time, an oleaginous yeast was cultured for over 2 months with a relatively stable lipid production rate (around 0.08 g L−1 h−1) and fatty acid profile (degree of fatty acid saturation around 27.6% w/w), and without contamination. On the 250-L scale, comparable results were observed, culminating in the generation of nearly 10 kg lipids with a lipid productivity of 0.10 g L−1 h−1. The results establish the importance of M. pulcherrima for industrial biotechnology and its suitability to commercially produce a food-grade oil. Further improvements in the productivity are required to make M. pulcherrima lipid production industrial reality, particularly when longer-chain saccharides are involved.

  • the role of temperature ph and nutrition in process development of the unique oleaginous yeast Metschnikowia pulcherrima
    Journal of Chemical Technology & Biotechnology, 2019
    Co-Authors: Felix Abeln, Christopher J. Chuck
    Abstract:

    BACKGROUND: Lipids produced from oleaginous yeasts are a promising alternative to terrestrial oils. Despite promising cellular yields of lipid however, an industrial process remains elusive. One key processing bottleneck is the need to provide nutrient‐rich conditions for cellular growth and then extended nutrient‐depleted conditions for lipid accumulation. Surprisingly, investigations detailing process development, particularly with a focus on kinetics, are rare in this field. RESULTS: In this investigation we report on the unique oleaginous yeast Metschnikowia pulcherrima, where lipid accumulation ≥ 29.8% (w/w) was achieved without apparent nutrient limitation. The process was developed in stirred tank reactors through determining the influence of temperature, pH and nutrition on lipid production. A temperature of up to 25 °C and initial pH 5 could be applied to enhance initial reaction kinetics. Through the increased supply of yeast extract of up to 5% (w/w) of glucose, a maximum lipid production rate of 0.60 g L⁻¹ h⁻¹ (4 h‐average), productivity of 0.29 g L⁻¹ h⁻¹, and yield of 0.17 g g⁻¹ glucose were achieved – the highest yet recorded with this yeast. Suitable to combat the excessive secretion of polyols of up to 0.11 g g⁻¹ glucose was an excess nutrient supply as well as a low cultivation temperature of 15 °C and moderate pH 5. CONCLUSIONS: This study demonstrates that the lack of a starvation stage, coupled with effective process development is required for oleaginous yeasts to achieve the yields and productivities required for commercial lipid production. © 2019 Society of Chemical Industry

  • achieving a high density oleaginous yeast culture comparison of four processing strategies using Metschnikowia pulcherrima
    Biotechnology and Bioengineering, 2019
    Co-Authors: Felix Abeln, Christopher J. Chuck
    Abstract:

    Microbial lipids have the potential to displace terrestrial oils for fuel, value chemical, and food production, curbing the growth in tropical oil plantations and helping to reduce deforestation. However, commercialization remains elusive partly due to the lack of suitably robust organisms and their low lipid productivity. Extremely high cell densities in oleaginous cultures are needed to increase reaction rates, reduce reactor volume, and facilitate downstream processing. In this investigation, the oleaginous yeast Metschnikowia pulcherrima, a known antimicrobial producer, was cultured using four different processing strategies to achieve high cell densities and gain suitable lipid productivity. In batch mode, the yeast demonstrated lipid contents more than 40% (w/w) under high osmotic pressure. In fed-batch mode, however, high-lipid titers were prevented through inhibition above 70.0 g L-1 yeast biomass. Highly promising were a semi-continuous and continuous mode with cell recycle where cell densities of up to 122.6 g L-1 and maximum lipid production rates of 0.37 g L-1  h-1 (daily average), a nearly two-fold increase from the batch, were achieved. The findings demonstrate the importance of considering multiple fermentation modes to achieve high-density oleaginous yeast cultures generally and indicate the limitations of processing these organisms under the extreme conditions necessary for economic lipid production.

  • lipid production through the single step microwave hydrolysis of macroalgae using the oleaginous yeast Metschnikowia pulcherrima
    Algal Research-Biomass Biofuels and Bioproducts, 2019
    Co-Authors: Felix Abeln, Daniel A Henk, Jiajun Fan, Vitaliy L Budarin, Hannah Briers, Sophie Parsons, Michael J Allen, James H Clark, Christopher J. Chuck
    Abstract:

    Abstract Macroalgae (seaweeds) represent an emerging resource for food and the production of commodity and specialty chemicals. In this study, a single-step microwave process was used to depolymerise a range of macroalgae native to the United Kingdom, producing a growth medium suitable for microbial fermentation. The medium contained a range of mono- and polysaccharides as well as macro- and micronutrients that could be metabolised by the oleaginous yeast Metschnikowia pulcherrima. Among twelve macroalgae species, the brown seaweeds exhibited the highest fermentation potential, especially the kelp Saccharina latissima. Applying a portfolio of ten native M. pulcherrima strains, yeast growth kinetics, as well as production of lipids and 2-phenylethanol were examined, with productivity and growth rate being strain dependent. On the 2 L scale, 6.9 g L−1 yeast biomass – a yield of 0.14 g g−1 with respect to the supplied macroalgae – containing 37.2% (w/w) lipid was achieved through utilisation of the proteins, mono- and polysaccharides from S. latissima, with no additional enzymes. In addition, the yeast degraded a range of fermentation inhibitors released upon microwave processing at high temperatures and long holding times. As macroalgae can be cultured to food grade, this system offers a novel, potentially low-cost route to edible microbial oils as well as a renewable feedstock for oleochemicals.