The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Yong Su Jin - One of the best experts on this subject based on the ideXlab platform.
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Enhanced Cellobiose fermentation by engineered Saccharomyces cerevisiae expressing a mutant cellodextrin facilitator and Cellobiose phosphorylase
Journal of biotechnology, 2018Co-Authors: Heejin Kim, Jamie H D Cate, Won-heong Lee, Stephan Lane, Yong Su JinAbstract:Abstract To efficiently ferment intermediate cellodextrins released during cellulose hydrolysis, Saccharomyces cerevisiae has been engineered by introduction of a heterologous cellodextrin utilizing pathway consisting of a cellodextrin transporter and either an intracellular β-glucosidase or a Cellobiose phosphorylase. Among two types of cellodextrin transporters, the passive facilitator CDT-2 has not enabled better Cellobiose fermentation than the active transporter CDT-1, which suggests that the CDT-2 might be engineered to provide energetic benefits over the active transporter in Cellobiose fermentation. We attempted to improve Cellobiose transporting activity of CDT-2 through laboratory evolution. Nine rounds of a serial subculture of S. cerevisiae expressing CDT-2 and Cellobiose phosphorylase on Cellobiose led to the isolation of an evolved strain capable of fermenting Cellobiose to ethanol 10-fold faster than the original strain. After sequence analysis of the isolated CDT-2, a single point mutation on CDT-2 (N306I) was revealed to be responsible for enhanced Cellobiose fermentation. Also, the engineered strain expressing the mutant CDT-2 with Cellobiose phosphorylase showed a higher ethanol yield than the engineered strain expressing CDT-1 and intracellular β-glucosidase under anaerobic conditions, suggesting that CDT-2 coupled with Cellobiose phosphorylase may be better choices for efficient production of cellulosic ethanol with the engineered yeast.
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development and physiological characterization of Cellobiose consuming yarrowia lipolytica
Biotechnology and Bioengineering, 2015Co-Authors: Yong Su Jin, Stephan Lane, Na Wei, Shuyan Zhang, Christopher V. RaoAbstract:Yarrowia lipolytica is a promising production host for a wide range of molecules, but limited sugar consumption abilities prevent utilization of an abundant source of renewable feedstocks. In this study we created a Y. lipolytica strain capable of utilizing Cellobiose as a sole carbon source by using endogenous promoters to express the cellodextrin transporter cdt-1 and intracellular β-glucosidase gh1-1 from Neurospora crassa. The engineered strain was also capable of simultaneous co-consumption of glucose and Cellobiose. Although Cellobiose was consumed slower than glucose when engineered strains were cultured with excess nitrogen, culturing with limited nitrogen led to Cellobiose consumption rates comparable to those of glucose. Under limited nitrogen conditions, the engineered strain produced citric acid as a major product and we observed greater citric acid yields from Cellobiose (0.37 g/g) than glucose (0.28 g/g). Culturing with a sole carbon source of either glucose or Cellobiose induced additional differences on cell physiology and metabolism and a link is suggested to evasion of glucose-sensing mechanisms through intracellular creation and consumption of glucose. We ultimately applied this Cellobiose-utilization system to produce citric acid from bioconversion of crystalline cellulose through simultaneous saccharification and fermentation (SSF).
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Development and physiological characterization of Cellobiose‐consuming Yarrowia lipolytica
Biotechnology and bioengineering, 2015Co-Authors: Stephan Lane, Na Wei, Shuyan Zhang, Christopher V. Rao, Yong Su JinAbstract:Yarrowia lipolytica is a promising production host for a wide range of molecules, but limited sugar consumption abilities prevent utilization of an abundant source of renewable feedstocks. In this study we created a Y. lipolytica strain capable of utilizing Cellobiose as a sole carbon source by using endogenous promoters to express the cellodextrin transporter cdt-1 and intracellular β-glucosidase gh1-1 from Neurospora crassa. The engineered strain was also capable of simultaneous co-consumption of glucose and Cellobiose. Although Cellobiose was consumed slower than glucose when engineered strains were cultured with excess nitrogen, culturing with limited nitrogen led to Cellobiose consumption rates comparable to those of glucose. Under limited nitrogen conditions, the engineered strain produced citric acid as a major product and we observed greater citric acid yields from Cellobiose (0.37 g/g) than glucose (0.28 g/g). Culturing with a sole carbon source of either glucose or Cellobiose induced additional differences on cell physiology and metabolism and a link is suggested to evasion of glucose-sensing mechanisms through intracellular creation and consumption of glucose. We ultimately applied this Cellobiose-utilization system to produce citric acid from bioconversion of crystalline cellulose through simultaneous saccharification and fermentation (SSF).
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Overcoming inefficient Cellobiose fermentation by Cellobiose phosphorylase in the presence of xylose
Biotechnology for biofuels, 2014Co-Authors: Kulika Chomvong, Jonathan M. Galazka, Yong Su Jin, Vesna Kordić, Stefan Bauer, Abigail E. Gillespie, Jamie H D CateAbstract:Cellobiose and xylose co-fermentation holds promise for efficiently producing biofuels from plant biomass. Cellobiose phosphorylase (CBP), an intracellular enzyme generally found in anaerobic bacteria, cleaves Cellobiose to glucose and glucose-1-phosphate, providing energetic advantages under the anaerobic conditions required for large-scale biofuel production. However, the efficiency of CBP to cleave Cellobiose in the presence of xylose is unknown. This study investigated the effect of xylose on anaerobic CBP-mediated Cellobiose fermentation by Saccharomyces cerevisiae. Yeast capable of fermenting Cellobiose by the CBP pathway consumed Cellobiose and produced ethanol at rates 61% and 42% slower, respectively, in the presence of xylose than in its absence. The system generated significant amounts of the byproduct 4-O-β-d-glucopyranosyl-d-xylose (GX), produced by CBP from glucose-1-phosphate and xylose. In vitro competition assays identified xylose as a mixed-inhibitor for Cellobiose phosphorylase activity. The negative effects of xylose were effectively relieved by efficient Cellobiose and xylose co-utilization. GX was also shown to be a substrate for cleavage by an intracellular β-glucosidase. Xylose exerted negative impacts on CBP-mediated Cellobiose fermentation by acting as a substrate for GX byproduct formation and a mixed-inhibitor for Cellobiose phosphorylase activity. Future efforts will require efficient xylose utilization, GX cleavage by a β-glucosidase, and/or a CBP with improved substrate specificity to overcome the negative impacts of xylose on CBP in Cellobiose and xylose co-fermentation.
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Molecular cloning and expression of fungal Cellobiose transporters and β-glucosidases conferring efficient Cellobiose fermentation in Saccharomyces cerevisiae
Journal of biotechnology, 2013Co-Authors: Yi-hyun Bae, Yong Su Jin, Kyeong Hyeon Kang, Jin-ho SeoAbstract:Abstract Cellobiose was once regarded as a byproduct that should be removed from biomass hydrolysates because of its inhibitory activity to cellulases. It was revealed, however, that Cellobiose could serve as a co-substrate for xylose fermentation by engineered Saccharomyces cerevisiae . Despite its advantages, to date, little is known about cellodextrin transporters that endow S. cerevisiae with Cellobiose transporting ability. In this study, engineered S. cerevisiae strains capable of fermenting Cellobiose were constructed by expressing various fungal Cellobiose transporters and intracellular β-glucosidases. Among them, the strain expressing a putative sugar transporter from Penicillium chrysogenum (Pc_ST) and β-glucosidase from Thielavia terrestris (Tt_BG) showed an improved Cellobiose fermentation performance compared to the strain expressing a cellodextrin transporter from Neurospora crassa (Nc_CDT-1) and β-glucosidase from N. crassa (Nc_GH1-1). Cellobiose fermentation by S. cerevisiae Pc_ST/Tt_BG under microaerobic conditions resulted in 14.5 ± 0.5 g/L of final ethanol concentration with a yield of 0.37 ± 0.01 g ethanol/g Cellobiose, which are 22% and 26% higher than the corresponding values of S. cerevisiae Nc_CDT-1/Nc_GH1-1. These results suggest that the yield and rate of Cellobiose fermentation can be improved by adopting optimal pairs of Cellobiose transporters and β-glucosidase.
Robert Landick - One of the best experts on this subject based on the ideXlab platform.
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heterologous expression of a glycosyl hydrolase and cellular reprogramming enable zymomonas mobilis growth on Cellobiose
PLOS ONE, 2020Co-Authors: Nagendra Prasad Kurumbang, Jessica M Vera, Alexander S Hebert, Joshua J Coon, Robert LandickAbstract:Plant-derived fuels and chemicals from renewable biomass have significant potential to replace reliance on petroleum and improve global carbon balance. However, plant biomass contains significant fractions of oligosaccharides that are not usable natively by many industrial microorganisms, including Escherichia coli, Saccharomyces cerevisiae, and Zymomonas mobilis. Even after chemical or enzymatic hydrolysis, some carbohydrate remains as non-metabolizable oligosaccharides (e.g., Cellobiose or longer cellulose-derived oligomers), thus reducing the efficiency of conversion to useful products. To begin to address this problem for Z. mobilis, we engineered a strain (Z. mobilis GH3) that expresses a glycosyl hydrolase (GH) with β-glucosidase activity from a related α-proteobacterial species, Caulobacter crescentus, and subjected it to an adaptation in Cellobiose medium. Growth on Cellobiose was achieved after a prolonged lag phase in Cellobiose medium that induced changes in gene expression and cell composition, including increased expression and extracellular release of GH. These changes were reversible upon growth in glucose-containing medium, meaning they did not result from genetic mutation but could be retained upon transfer of cells to fresh Cellobiose medium. After adaptation to Cellobiose, our GH-expressing strain was able to convert about 50% of Cellobiose to glucose within 24 h and use it for growth and ethanol production. Alternatively, pre-growth of Z. mobilis GH3 in sucrose medium enabled immediate growth on Cellobiose. Proteomic analysis of Cellobiose- and sucrose-adapted strains revealed upregulation of secretion-, transport-, and outer membrane-related proteins, which may aid release or surface display of GHs, entry of Cellobiose into the periplasm, or both. Our two key findings are that Z. mobilis can be reprogrammed to grow on Cellobiose as a sole carbon source and that this reprogramming is related to a natural response of Z. mobilis to sucrose that promotes sucrase production.
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heterologous glycosyl hydrolase expression and cellular reprogramming resembling sucrose induction enable zymomonas mobilis growth on Cellobiose
bioRxiv, 2019Co-Authors: Nagendra Prasad Kurumbang, Jessica M Vera, Alexander S Hebert, Joshua J Coon, Robert LandickAbstract:Plant derived fuels and chemicals from renewable biomass have significant potential to replace reliance on petroleum and improve global carbon balance. However, plant biomass contains significant fractions of oligosaccharides that are not usable natively by many industrial microorganisms, including Escherichia coli, Saccharomyces cerevisiae, and Zymomonas mobilis. Even after chemical or enzymatic hydrolysis, some carbohydrate remains as non-metabolizable oligosaccharides (e.g., Cellobiose or longer cellulose-derived oligomers), thus reducing the efficiency of conversion to useful products. To begin to address this problem for Z. mobilis, we engineered a strain (Z. mobilis GH3) that expresses a glycosyl hydrolase (GH) with β-glucosidase activity from Caulobacter crescentus and subjected it to an adaptation in Cellobiose medium. Growth on Cellobiose was achieved after a prolonged lag phase in Cellobiose medium that induced changes in gene expression and cell composition, including increased expression and secretion of GH. These changes were reversible upon growth in glucose-containing medium, meaning they did not result from genetic mutation but could be retained upon transfer of cells to fresh Cellobiose medium. After adaptation to Cellobiose, our GH-expressing strain was able to convert about 50% of Cellobiose to glucose within 24 hours and use it for growth and ethanol production. Alternatively, pre-growth of Z. mobilis GH3 in sucrose medium enabled immediate growth on Cellobiose. Proteomic analysis of Cellobiose- and sucrose-adapted strains revealed upregulation of secretion-, transport-, and outer membrane-related proteins, which may aid secretion or surface display of GHs, entry of Cellobiose into the periplasm, or both. Our two key findings are that Z. mobilis can be reprogrammed to grow on Cellobiose as a sole carbon source and that this reprogramming is related to a natural response of Z. mobilis to sucrose that enables sucrose secretion.
Jamie H D Cate - One of the best experts on this subject based on the ideXlab platform.
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Enhanced Cellobiose fermentation by engineered Saccharomyces cerevisiae expressing a mutant cellodextrin facilitator and Cellobiose phosphorylase
Journal of biotechnology, 2018Co-Authors: Heejin Kim, Jamie H D Cate, Won-heong Lee, Stephan Lane, Yong Su JinAbstract:Abstract To efficiently ferment intermediate cellodextrins released during cellulose hydrolysis, Saccharomyces cerevisiae has been engineered by introduction of a heterologous cellodextrin utilizing pathway consisting of a cellodextrin transporter and either an intracellular β-glucosidase or a Cellobiose phosphorylase. Among two types of cellodextrin transporters, the passive facilitator CDT-2 has not enabled better Cellobiose fermentation than the active transporter CDT-1, which suggests that the CDT-2 might be engineered to provide energetic benefits over the active transporter in Cellobiose fermentation. We attempted to improve Cellobiose transporting activity of CDT-2 through laboratory evolution. Nine rounds of a serial subculture of S. cerevisiae expressing CDT-2 and Cellobiose phosphorylase on Cellobiose led to the isolation of an evolved strain capable of fermenting Cellobiose to ethanol 10-fold faster than the original strain. After sequence analysis of the isolated CDT-2, a single point mutation on CDT-2 (N306I) was revealed to be responsible for enhanced Cellobiose fermentation. Also, the engineered strain expressing the mutant CDT-2 with Cellobiose phosphorylase showed a higher ethanol yield than the engineered strain expressing CDT-1 and intracellular β-glucosidase under anaerobic conditions, suggesting that CDT-2 coupled with Cellobiose phosphorylase may be better choices for efficient production of cellulosic ethanol with the engineered yeast.
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Overcoming inefficient Cellobiose fermentation by Cellobiose phosphorylase in the presence of xylose
Biotechnology for biofuels, 2014Co-Authors: Kulika Chomvong, Jonathan M. Galazka, Yong Su Jin, Vesna Kordić, Stefan Bauer, Abigail E. Gillespie, Jamie H D CateAbstract:Cellobiose and xylose co-fermentation holds promise for efficiently producing biofuels from plant biomass. Cellobiose phosphorylase (CBP), an intracellular enzyme generally found in anaerobic bacteria, cleaves Cellobiose to glucose and glucose-1-phosphate, providing energetic advantages under the anaerobic conditions required for large-scale biofuel production. However, the efficiency of CBP to cleave Cellobiose in the presence of xylose is unknown. This study investigated the effect of xylose on anaerobic CBP-mediated Cellobiose fermentation by Saccharomyces cerevisiae. Yeast capable of fermenting Cellobiose by the CBP pathway consumed Cellobiose and produced ethanol at rates 61% and 42% slower, respectively, in the presence of xylose than in its absence. The system generated significant amounts of the byproduct 4-O-β-d-glucopyranosyl-d-xylose (GX), produced by CBP from glucose-1-phosphate and xylose. In vitro competition assays identified xylose as a mixed-inhibitor for Cellobiose phosphorylase activity. The negative effects of xylose were effectively relieved by efficient Cellobiose and xylose co-utilization. GX was also shown to be a substrate for cleavage by an intracellular β-glucosidase. Xylose exerted negative impacts on CBP-mediated Cellobiose fermentation by acting as a substrate for GX byproduct formation and a mixed-inhibitor for Cellobiose phosphorylase activity. Future efforts will require efficient xylose utilization, GX cleavage by a β-glucosidase, and/or a CBP with improved substrate specificity to overcome the negative impacts of xylose on CBP in Cellobiose and xylose co-fermentation.
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Single Amino Acid Substitutions in HXT2.4 from Scheffersomyces stipitis Lead to Improved Cellobiose Fermentation by Engineered Saccharomyces cerevisiae
Applied and environmental microbiology, 2012Co-Authors: Heejin Kim, Jamie H D Cate, Jonathan M. Galazka, Yuping Lin, Myoung Uoon Jang, Tae Jip Kim, Yong Su JinAbstract:Saccharomyces cerevisiae cannot utilize Cellobiose, but this yeast can be engineered to ferment Cellobiose by introducing both cellodextrin transporter (cdt-1) and intracellular β-glucosidase (gh1-1) genes from Neurospora crassa. Here, we report that an engineered S. cerevisiae strain expressing the putative hexose transporter gene HXT2.4 from Scheffersomyces stipitis and gh1-1 can also ferment Cellobiose. This result suggests that HXT2.4p may function as a Cellobiose transporter when HXT2.4 is overexpressed in S. cerevisiae. However, Cellobiose fermentation by the engineered strain expressing HXT2.4 and gh1-1 was much slower and less efficient than that by an engineered strain that initially expressed cdt-1 and gh1-1. The rate of Cellobiose fermentation by the HXT2.4-expressing strain increased drastically after serial subcultures on Cellobiose. Sequencing and retransformation of the isolated plasmids from a single colony of the fast Cellobiose-fermenting culture led to the identification of a mutation (A291D) in HXT2.4 that is responsible for improved Cellobiose fermentation by the evolved S. cerevisiae strain. Substitutions for alanine (A291) of negatively charged amino acids (A291E and A291D) or positively charged amino acids (A291K and A291R) significantly improved Cellobiose fermentation. The mutant HXT2.4(A291D) exhibited 1.5-fold higher Km and 4-fold higher Vmax values than those from wild-type HXT2.4, whereas the expression levels were the same. These results suggest that the kinetic properties of wild-type HXT2.4 expressed in S. cerevisiae are suboptimal, and mutations of A291 into bulky charged amino acids might transform HXT2.4p into an efficient transporter, enabling rapid Cellobiose fermentation by engineered S. cerevisiae strains.
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Energetic benefits and rapid Cellobiose fermentation by Saccharomyces cerevisiae expressing Cellobiose phosphorylase and mutant cellodextrin transporters
Metabolic engineering, 2012Co-Authors: Jonathan M. Galazka, Yong Su Jin, Heejin Kim, Vesna Kordić, Jamie H D CateAbstract:Anaerobic bacteria assimilate cellodextrins from plant biomass by using a phosphorolytic pathway to generate glucose intermediates for growth. The yeast Saccharomyces cerevisiae can also be engineered to ferment Cellobiose to ethanol using a cellodextrin transporter and a phosphorolytic pathway. However, strains with an intracellular Cellobiose phosphorylase initially fermented Cellobiose slowly relative to a strain employing an intracellular β-glucosidase. Fermentations by the phosphorolytic strains were greatly improved by using cellodextrin transporters with elevated rates of Cellobiose transport. Furthermore under stress conditions, these phosphorolytic strains had higher biomass and ethanol yields compared to hydrolytic strains. These observations suggest that, although Cellobiose phosphorolysis has energetic advantages, phosphorolytic strains are limited by the thermodynamics of Cellobiose phosphorolysis (ΔG°=+3.6kJmol(-1)). A thermodynamic "push" from the reaction immediately upstream (transport) is therefore likely to be necessary to achieve high fermentation rates and energetic benefits of phosphorolysis pathways in engineered S. cerevisiae.
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Cellobiose dehydrogenase and a copper dependent polysaccharide monooxygenase potentiate cellulose degradation by neurospora crassa
ACS Chemical Biology, 2011Co-Authors: Christopher M Phillips, William T Beeson, Jamie H D Cate, Michael A MarlettaAbstract:The high cost of enzymes for saccharification of lignocellulosic biomass is a major barrier to the production of second generation biofuels. Using a combination of genetic and biochemical techniques, we report that filamentous fungi use oxidative enzymes to cleave glycosidic bonds in cellulose. Deletion of cdh-1, the gene encoding the major Cellobiose dehydrogenase of Neurospora crassa, reduced cellulase activity substantially, and addition of purified Cellobiose dehydrogenases from M. thermophila to the Δcdh-1 strain resulted in a 1.6- to 2.0-fold stimulation in cellulase activity. Addition of Cellobiose dehydrogenase to a mixture of purified cellulases showed no stimulatory effect. We show that Cellobiose dehydrogenase enhances cellulose degradation by coupling the oxidation of Cellobiose to the reductive activation of copper-dependent polysaccharide monooxygenases (PMOs) that catalyze the insertion of oxygen into C–H bonds adjacent to the glycosidic linkage. Three of these PMOs were characterized and s...
Stephan Lane - One of the best experts on this subject based on the ideXlab platform.
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Enhanced Cellobiose fermentation by engineered Saccharomyces cerevisiae expressing a mutant cellodextrin facilitator and Cellobiose phosphorylase
Journal of biotechnology, 2018Co-Authors: Heejin Kim, Jamie H D Cate, Won-heong Lee, Stephan Lane, Yong Su JinAbstract:Abstract To efficiently ferment intermediate cellodextrins released during cellulose hydrolysis, Saccharomyces cerevisiae has been engineered by introduction of a heterologous cellodextrin utilizing pathway consisting of a cellodextrin transporter and either an intracellular β-glucosidase or a Cellobiose phosphorylase. Among two types of cellodextrin transporters, the passive facilitator CDT-2 has not enabled better Cellobiose fermentation than the active transporter CDT-1, which suggests that the CDT-2 might be engineered to provide energetic benefits over the active transporter in Cellobiose fermentation. We attempted to improve Cellobiose transporting activity of CDT-2 through laboratory evolution. Nine rounds of a serial subculture of S. cerevisiae expressing CDT-2 and Cellobiose phosphorylase on Cellobiose led to the isolation of an evolved strain capable of fermenting Cellobiose to ethanol 10-fold faster than the original strain. After sequence analysis of the isolated CDT-2, a single point mutation on CDT-2 (N306I) was revealed to be responsible for enhanced Cellobiose fermentation. Also, the engineered strain expressing the mutant CDT-2 with Cellobiose phosphorylase showed a higher ethanol yield than the engineered strain expressing CDT-1 and intracellular β-glucosidase under anaerobic conditions, suggesting that CDT-2 coupled with Cellobiose phosphorylase may be better choices for efficient production of cellulosic ethanol with the engineered yeast.
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development and physiological characterization of Cellobiose consuming yarrowia lipolytica
Biotechnology and Bioengineering, 2015Co-Authors: Yong Su Jin, Stephan Lane, Na Wei, Shuyan Zhang, Christopher V. RaoAbstract:Yarrowia lipolytica is a promising production host for a wide range of molecules, but limited sugar consumption abilities prevent utilization of an abundant source of renewable feedstocks. In this study we created a Y. lipolytica strain capable of utilizing Cellobiose as a sole carbon source by using endogenous promoters to express the cellodextrin transporter cdt-1 and intracellular β-glucosidase gh1-1 from Neurospora crassa. The engineered strain was also capable of simultaneous co-consumption of glucose and Cellobiose. Although Cellobiose was consumed slower than glucose when engineered strains were cultured with excess nitrogen, culturing with limited nitrogen led to Cellobiose consumption rates comparable to those of glucose. Under limited nitrogen conditions, the engineered strain produced citric acid as a major product and we observed greater citric acid yields from Cellobiose (0.37 g/g) than glucose (0.28 g/g). Culturing with a sole carbon source of either glucose or Cellobiose induced additional differences on cell physiology and metabolism and a link is suggested to evasion of glucose-sensing mechanisms through intracellular creation and consumption of glucose. We ultimately applied this Cellobiose-utilization system to produce citric acid from bioconversion of crystalline cellulose through simultaneous saccharification and fermentation (SSF).
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Development and physiological characterization of Cellobiose‐consuming Yarrowia lipolytica
Biotechnology and bioengineering, 2015Co-Authors: Stephan Lane, Na Wei, Shuyan Zhang, Christopher V. Rao, Yong Su JinAbstract:Yarrowia lipolytica is a promising production host for a wide range of molecules, but limited sugar consumption abilities prevent utilization of an abundant source of renewable feedstocks. In this study we created a Y. lipolytica strain capable of utilizing Cellobiose as a sole carbon source by using endogenous promoters to express the cellodextrin transporter cdt-1 and intracellular β-glucosidase gh1-1 from Neurospora crassa. The engineered strain was also capable of simultaneous co-consumption of glucose and Cellobiose. Although Cellobiose was consumed slower than glucose when engineered strains were cultured with excess nitrogen, culturing with limited nitrogen led to Cellobiose consumption rates comparable to those of glucose. Under limited nitrogen conditions, the engineered strain produced citric acid as a major product and we observed greater citric acid yields from Cellobiose (0.37 g/g) than glucose (0.28 g/g). Culturing with a sole carbon source of either glucose or Cellobiose induced additional differences on cell physiology and metabolism and a link is suggested to evasion of glucose-sensing mechanisms through intracellular creation and consumption of glucose. We ultimately applied this Cellobiose-utilization system to produce citric acid from bioconversion of crystalline cellulose through simultaneous saccharification and fermentation (SSF).
B A White - One of the best experts on this subject based on the ideXlab platform.
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Cellobiose uptake and metabolism by Ruminococcus flavefaciens.
Applied and environmental microbiology, 1991Co-Authors: C T Helaszek, B A WhiteAbstract:The cellulolytic ruminal bacterium Ruminococcus flavefaciens FD-1 utilizes Cellobiose but not glucose as a substrate for growth. Cellobiose uptake by R. flavefaciens FD-1 was measured under anaerobic conditions (N2), using [G-3H]Cellobiose. The rate of Cellobiose uptake for early- or late-log-phase Cellobiose-grown cells was 9 nmol/min per mg of whole-cell protein. Cellobiose uptake was inhibited by electron transport inhibitors, iron-reactive compounds, proton ionophores, sulfhydryl inhibitors, N,N-dicyclohexylcarbodiimide, and NaF, as well as lasalocid and monensin. The results support the existence of an active transport system for Cellobiose. Transport of [U-14C]glucose was not detected with this system. Phosphorylation of Cellobiose was not by a phosphoenolpyruvate-dependent system. Cellobiose phosphorylase activity was detected by both a coupled spectrophotometric assay and a discontinuous assay. The enzyme was produced constitutively in Cellobiose-grown cells at a specific activity of 329 nmol/min per mg of cell-free extract protein.