Propanoic acid accumulated in an ethanol-methane coupled fermentation process affects the ethanol fermentation by Saccharomyces cerevisiae. The effects of propanoic acid on ethanol production were examined in cassava ...Propanoic acid accumulated in an ethanol-methane coupled fermentation process affects the ethanol fermentation by Saccharomyces cerevisiae. The effects of propanoic acid on ethanol production were examined in cassava mash under different pH conditions. Final ethanol concentrations increased when undissociated propanoic acid was <30.0 mmol·L-1 . Propanoic acid, however, stimulated ethanol production, as much as 7.6% under proper conditions, but ethanol fermentation was completely inhibited when undissociated acid was >53.2 mmol·L-1 . Therefore, the potential inhibitory effect of propanoic acid on ethanol fermentation may be avoided by controlling the undissociated acid concentrations through elevated medium pH. Biomass and glycerol production decreased with propanoic acid in the medium, partly contributing to increased ethanol concentration.展开更多
In ethanol fermentation of Saccharomyces cerevisiae （S. cerevisiae）, glycerol is one of the main by-products. The purpose of this investigation was to increase ethanol yield through minimizing glycerol yield by usin...In ethanol fermentation of Saccharomyces cerevisiae （S. cerevisiae）, glycerol is one of the main by-products. The purpose of this investigation was to increase ethanol yield through minimizing glycerol yield by using mutants in which FPS1 encoding a channel protein that mediates glycerol export and GPD2 encoding one of glycerol-3-phosphate dehydrogenase were knocked-out using one-step gene replacement. GLT1 and GLN1 that encode glutamate synthase and glutamine synth.etase, respectively,were overexpressed using two-step gene replacment in fpsl△gpd2△ mutant.The fermentation properties of ZAL69（fpsl△：：LEU2 gpd2△：：URA3） and ZAL808 （fps1△：：LEU2 gpd2△：：URA3 PPGK1-GLT1 PPGK1-GLN1） under microaerobic conditions were investigated and compared with those of wild type（DC124）. Consumption of glucose, yield of ethanol, yield of glycerol, acetic acid, and pyruvic acid were monitored. Compared with wild type, the ethanol yield of ZAL69 and ZAL808 were improved by. 13.17% and 6.66 %, respectively, whereas glycerol yield decreased by 37.4 % and 41.7 %. Meanwhile, acetic acia yield and pyruvic acid yield aecreasea aramatlcally comparea to wild type. Our results indicate that FPS1 and GPD2 deletion of S. cerevisiae resulted in reduced glycerol yield and increased ethanol yield, but simultaneous overexpression of GLT1 and GLN1 infps1△gpd2△ mutant did not have a higher ethanol yield thanfps1△gpd2△ mutant.展开更多
The feasibility of pilot-scale manufacture of defined fungal starter and its application in rice wine production from different local starchy materials were investigated. Starter consisting of Arnylomyces rouxii and S...The feasibility of pilot-scale manufacture of defined fungal starter and its application in rice wine production from different local starchy materials were investigated. Starter consisting of Arnylomyces rouxii and Saccharomyces cerevisiae gave high performance in winemaking when prepared in conditions of rice flour 80% and cassava flour 20% with 4 incubation days. The starter level at 20% was favourably employed for manufacture with the initial amount of I0 kg mixed-flours, Dry starter granules which were vacuum packed could adapt ambient temperature （approx. 28-32℃） during 8 months of storage. The defined starter performed as superior inoculum for winemaking from different agricultural starchy resources. The undesirable bacteria were found at approx. 2 Log CFU/g of dry starter. By morphology, biochemical and physiological growth and the genetic partial 16S analyses, three bacterial isolates were characterized as Bacillus subtilis/amvloliquefaciens which may contaminate tbod but not cause food poisoning and not considered as a human pathogen.展开更多
基金Supported by the National High Technology Research and Development Program of China (2008AA10Z338)
文摘Propanoic acid accumulated in an ethanol-methane coupled fermentation process affects the ethanol fermentation by Saccharomyces cerevisiae. The effects of propanoic acid on ethanol production were examined in cassava mash under different pH conditions. Final ethanol concentrations increased when undissociated propanoic acid was <30.0 mmol·L-1 . Propanoic acid, however, stimulated ethanol production, as much as 7.6% under proper conditions, but ethanol fermentation was completely inhibited when undissociated acid was >53.2 mmol·L-1 . Therefore, the potential inhibitory effect of propanoic acid on ethanol fermentation may be avoided by controlling the undissociated acid concentrations through elevated medium pH. Biomass and glycerol production decreased with propanoic acid in the medium, partly contributing to increased ethanol concentration.
基金the National High Technology Research and Development Program of China(2002AA647040)
文摘In ethanol fermentation of Saccharomyces cerevisiae （S. cerevisiae）, glycerol is one of the main by-products. The purpose of this investigation was to increase ethanol yield through minimizing glycerol yield by using mutants in which FPS1 encoding a channel protein that mediates glycerol export and GPD2 encoding one of glycerol-3-phosphate dehydrogenase were knocked-out using one-step gene replacement. GLT1 and GLN1 that encode glutamate synthase and glutamine synth.etase, respectively,were overexpressed using two-step gene replacment in fpsl△gpd2△ mutant.The fermentation properties of ZAL69（fpsl△：：LEU2 gpd2△：：URA3） and ZAL808 （fps1△：：LEU2 gpd2△：：URA3 PPGK1-GLT1 PPGK1-GLN1） under microaerobic conditions were investigated and compared with those of wild type（DC124）. Consumption of glucose, yield of ethanol, yield of glycerol, acetic acid, and pyruvic acid were monitored. Compared with wild type, the ethanol yield of ZAL69 and ZAL808 were improved by. 13.17% and 6.66 %, respectively, whereas glycerol yield decreased by 37.4 % and 41.7 %. Meanwhile, acetic acia yield and pyruvic acid yield aecreasea aramatlcally comparea to wild type. Our results indicate that FPS1 and GPD2 deletion of S. cerevisiae resulted in reduced glycerol yield and increased ethanol yield, but simultaneous overexpression of GLT1 and GLN1 infps1△gpd2△ mutant did not have a higher ethanol yield thanfps1△gpd2△ mutant.
文摘The feasibility of pilot-scale manufacture of defined fungal starter and its application in rice wine production from different local starchy materials were investigated. Starter consisting of Arnylomyces rouxii and Saccharomyces cerevisiae gave high performance in winemaking when prepared in conditions of rice flour 80% and cassava flour 20% with 4 incubation days. The starter level at 20% was favourably employed for manufacture with the initial amount of I0 kg mixed-flours, Dry starter granules which were vacuum packed could adapt ambient temperature （approx. 28-32℃） during 8 months of storage. The defined starter performed as superior inoculum for winemaking from different agricultural starchy resources. The undesirable bacteria were found at approx. 2 Log CFU/g of dry starter. By morphology, biochemical and physiological growth and the genetic partial 16S analyses, three bacterial isolates were characterized as Bacillus subtilis/amvloliquefaciens which may contaminate tbod but not cause food poisoning and not considered as a human pathogen.
