ln this study, effects of UV irradiation and 60Co-γ irradiation on fermenta-tion of xylose to ethanol by Pichia stipitis were analyzed to investigate the optimal mutagenic conditions. According to the growth curve an...ln this study, effects of UV irradiation and 60Co-γ irradiation on fermenta-tion of xylose to ethanol by Pichia stipitis were analyzed to investigate the optimal mutagenic conditions. According to the growth curve and fermentation curve of P. stipi-tis, the optimal incubation duration and fermentation duration of P. stipitis mutant strain were 18 and 48 h, respectively. The cel concentration of original yeast liquid was 107 cel s/ml. After mutagenesis by UV irradiation and 60Co-γ irradiation, yeast liquid was incubated in 20 g/L xylose media for 48 h. According to the results, after UV irradiation for 45-75 s, transformation efficiency reached 0.3794 g/g, which was 74.39% of the theoretical value; after irradiation with 800-1 000 Gy 60Co-γ, transforma-tion efficiency reached 0.3165 g/g, which was 62.06% of the theoretical value. Therefore, both UV irradiation and 60Co-γ irradiation could improve the efficiency of xylose fermentation to ethanol by P. stipitis under appropriate conditions.展开更多
In this study, the rice straw was hydrolysed by using 3.0% （w/v） H2SO4 followed by enzymatic hydrolysis. The rice straw hydrolysate obtained was treated with charcoal powder and the optimal condition of detoxificati...In this study, the rice straw was hydrolysed by using 3.0% （w/v） H2SO4 followed by enzymatic hydrolysis. The rice straw hydrolysate obtained was treated with charcoal powder and the optimal condition of detoxification with charcoal powder was investigated. The results showed that the optimal condition for detoxification was the use of 2.5 grams of non-sterilized charcoal powder in 100 mL hydrolysate. The mixture was operated at pH 5.0, 30 ℃ and 160 rpm for 5 min. The detoxified hydrolysate was then used for ethanol production using P. stipitis TISTR 5806. The condition of the detoxified hydrolysate fermentation which gave maximum ethanol concentration of 21 g/L was at pH 5.0, 30 ℃ and 160 rpm for 72 h. Without detoxification, the P. stipitis TISTR 5806 could not however utilize the hydrolysate for ethanol production.展开更多
Pichia stipitis CBS 5773 yeast cells were used to ferment the mixed substrates consisted of glucose andxylose to produce ethanol.The effects of aeration rate,initial substrate concentration and pH on substrateutilizat...Pichia stipitis CBS 5773 yeast cells were used to ferment the mixed substrates consisted of glucose andxylose to produce ethanol.The effects of aeration rate,initial substrate concentration and pH on substrateutilization and ethanol yield were evaluated.During batch fermentation,the oscillation phenomena in cell growthwere observed at low aeration rate,whereas the diauxic growth at high aeration rate.The substrate utilizationratio and ethanol yield reached 95％ and 0.46g/g respectively under appropriate operation conditions.Amodified unstructural model was proposed to simulate the diauxic cell growth,substrate consumption andproduct formation.展开更多
Background:The high rate of propagation and easy availability of water hyacinth has made it a renewable carbon source for biofuel production.The present study was undertaken to screen the feasibility of using water hy...Background:The high rate of propagation and easy availability of water hyacinth has made it a renewable carbon source for biofuel production.The present study was undertaken to screen the feasibility of using water hyacinth's hemicelluloses as a substrate for alcohol production by microbial fermentation using mono and co-cultures of Trichoderma reesei and Fusarium oxysporum with Pichia stipitis.Results:In separate hydrolysis and fermentation(SHF),the alkali pretreated water hyacinth biomass was saccharified by crude fungal enzymes of T.reesei,F.oxysporum and then fermented by P.stipitis.In simultaneous saccharification and fermentation(SSF),the saccharification and fermentation was carried out simultaneously at optimized conditions using mono and co-cultures of selected fungal strains.Finally,the ethanol production kinetics were analyzed by appropriate methods.The higher crystalline index(66.7%)and the Fourier transform infrared(FTIR)spectra showed that the lime pretreatment possibly increased the availability of cellulose and hemicelluloses for enzymatic conversion.In SSF,the co-culture fermentation using T.reesei and P.stipitis was found to be promising with a higher yield of ethanol(0.411 g g^(−1))at 60 h.The additional yield comparable with the monocultures was due to the xylanolytic activity of P.stipitis which ferments pentose sugars into ethanol.In SHF,the pretreatment followed by crude enzymatic hydrolysis and fermentation resulted in a significantly lesser yield of ethanol(0.344 g g^(−1))at 96 h.Conclusions:It is evident from the study that the higher ethanol production was attained in a shorter period in the co-culture system containing T.reesei and the xylose fermenting yeast P.stipitis.SSF of pretreated water hyacinth biomass(WHB)with P.stipitis instead of traditional yeast is found to be an effective biofuel production process.展开更多
Microbial production of chemicals and proteins from biomass-derived andwaste sugar streams is a rapidly growing area of research and development.While the model yeast Saccharomyces cerevisiae is an excellent host for ...Microbial production of chemicals and proteins from biomass-derived andwaste sugar streams is a rapidly growing area of research and development.While the model yeast Saccharomyces cerevisiae is an excellent host for the conversion of glucose to ethanol,production of other chemicals from alternative substrates often requires extensive strain engineering.To avoid complex and intensive engineering of S.cerevisiae,other yeasts are often selected as hosts for bioprocessing based on their natural capacity to produce a desired product:for example,the efficient production and secretion of proteins,lipids,and primary metabolites that have value as commodity chemicals.Even when using yeasts with beneficial native phenotypes,metabolic engineering to increase yield,titer,and production rate is essential.The non-conventional yeasts Kluyveromyces lactis,K.marxianus,Scheffersomyces stipitis,Yarrowia lipolytica,Hansenula polymorpha and Pichia pastoris have been developed as eukaryotic hosts because of their desirable phenotypes,including thermotolerance,assimilation of diverse carbon sources,and high protein secretion.However,advanced metabolic engineering in these yeasts has been limited.This review outlines the challenges of using non-conventional yeasts for strain and pathway engineering,and discusses the developed solutions to these problems and the resulting applications in industrial biotechnology.展开更多
文摘ln this study, effects of UV irradiation and 60Co-γ irradiation on fermenta-tion of xylose to ethanol by Pichia stipitis were analyzed to investigate the optimal mutagenic conditions. According to the growth curve and fermentation curve of P. stipi-tis, the optimal incubation duration and fermentation duration of P. stipitis mutant strain were 18 and 48 h, respectively. The cel concentration of original yeast liquid was 107 cel s/ml. After mutagenesis by UV irradiation and 60Co-γ irradiation, yeast liquid was incubated in 20 g/L xylose media for 48 h. According to the results, after UV irradiation for 45-75 s, transformation efficiency reached 0.3794 g/g, which was 74.39% of the theoretical value; after irradiation with 800-1 000 Gy 60Co-γ, transforma-tion efficiency reached 0.3165 g/g, which was 62.06% of the theoretical value. Therefore, both UV irradiation and 60Co-γ irradiation could improve the efficiency of xylose fermentation to ethanol by P. stipitis under appropriate conditions.
文摘In this study, the rice straw was hydrolysed by using 3.0% （w/v） H2SO4 followed by enzymatic hydrolysis. The rice straw hydrolysate obtained was treated with charcoal powder and the optimal condition of detoxification with charcoal powder was investigated. The results showed that the optimal condition for detoxification was the use of 2.5 grams of non-sterilized charcoal powder in 100 mL hydrolysate. The mixture was operated at pH 5.0, 30 ℃ and 160 rpm for 5 min. The detoxified hydrolysate was then used for ethanol production using P. stipitis TISTR 5806. The condition of the detoxified hydrolysate fermentation which gave maximum ethanol concentration of 21 g/L was at pH 5.0, 30 ℃ and 160 rpm for 72 h. Without detoxification, the P. stipitis TISTR 5806 could not however utilize the hydrolysate for ethanol production.
文摘Pichia stipitis CBS 5773 yeast cells were used to ferment the mixed substrates consisted of glucose andxylose to produce ethanol.The effects of aeration rate,initial substrate concentration and pH on substrateutilization and ethanol yield were evaluated.During batch fermentation,the oscillation phenomena in cell growthwere observed at low aeration rate,whereas the diauxic growth at high aeration rate.The substrate utilizationratio and ethanol yield reached 95％ and 0.46g/g respectively under appropriate operation conditions.Amodified unstructural model was proposed to simulate the diauxic cell growth,substrate consumption andproduct formation.
文摘Background:The high rate of propagation and easy availability of water hyacinth has made it a renewable carbon source for biofuel production.The present study was undertaken to screen the feasibility of using water hyacinth's hemicelluloses as a substrate for alcohol production by microbial fermentation using mono and co-cultures of Trichoderma reesei and Fusarium oxysporum with Pichia stipitis.Results:In separate hydrolysis and fermentation(SHF),the alkali pretreated water hyacinth biomass was saccharified by crude fungal enzymes of T.reesei,F.oxysporum and then fermented by P.stipitis.In simultaneous saccharification and fermentation(SSF),the saccharification and fermentation was carried out simultaneously at optimized conditions using mono and co-cultures of selected fungal strains.Finally,the ethanol production kinetics were analyzed by appropriate methods.The higher crystalline index(66.7%)and the Fourier transform infrared(FTIR)spectra showed that the lime pretreatment possibly increased the availability of cellulose and hemicelluloses for enzymatic conversion.In SSF,the co-culture fermentation using T.reesei and P.stipitis was found to be promising with a higher yield of ethanol(0.411 g g^(−1))at 60 h.The additional yield comparable with the monocultures was due to the xylanolytic activity of P.stipitis which ferments pentose sugars into ethanol.In SHF,the pretreatment followed by crude enzymatic hydrolysis and fermentation resulted in a significantly lesser yield of ethanol(0.344 g g^(−1))at 96 h.Conclusions:It is evident from the study that the higher ethanol production was attained in a shorter period in the co-culture system containing T.reesei and the xylose fermenting yeast P.stipitis.SSF of pretreated water hyacinth biomass(WHB)with P.stipitis instead of traditional yeast is found to be an effective biofuel production process.
基金This work was supported by NSF CBET-1510697 and -1403264.
文摘Microbial production of chemicals and proteins from biomass-derived andwaste sugar streams is a rapidly growing area of research and development.While the model yeast Saccharomyces cerevisiae is an excellent host for the conversion of glucose to ethanol,production of other chemicals from alternative substrates often requires extensive strain engineering.To avoid complex and intensive engineering of S.cerevisiae,other yeasts are often selected as hosts for bioprocessing based on their natural capacity to produce a desired product:for example,the efficient production and secretion of proteins,lipids,and primary metabolites that have value as commodity chemicals.Even when using yeasts with beneficial native phenotypes,metabolic engineering to increase yield,titer,and production rate is essential.The non-conventional yeasts Kluyveromyces lactis,K.marxianus,Scheffersomyces stipitis,Yarrowia lipolytica,Hansenula polymorpha and Pichia pastoris have been developed as eukaryotic hosts because of their desirable phenotypes,including thermotolerance,assimilation of diverse carbon sources,and high protein secretion.However,advanced metabolic engineering in these yeasts has been limited.This review outlines the challenges of using non-conventional yeasts for strain and pathway engineering,and discusses the developed solutions to these problems and the resulting applications in industrial biotechnology.
