The shortage of petroleum has resulted in worldwide efforts to produce chemicals from renewable resources. Among these attempts, the possibility of producing acrylic acid from biomass has caught the eye of many resear...The shortage of petroleum has resulted in worldwide efforts to produce chemicals from renewable resources. Among these attempts, the possibility of producing acrylic acid from biomass has caught the eye of many researchers. Converting the carbohydrates first to lactic acid by fermentation and then dehydrating lactic acid to acrylic acid is hitherto the most effective way for producing acrylic acid from biomass. While the lactic acid fer- mentation has been commercialized since longer times, the dehydration process of lactic acid is still under development because of its low yield. Further efforts should be made before this process became economically feasible. Because of the existence of acrylic acid pathways in some microorganisms, strain improvement and metabolic engineering provides also a possibilitv to produce acrylic acid directly from biomass by fermentation.展开更多
Levulinic acid is a kind of new green platform chemical with wide application. The kinetics of levulinic acid formation from glucose decomposition at high temperature was investigated. Glucose containing 1%, 3% or 5% ...Levulinic acid is a kind of new green platform chemical with wide application. The kinetics of levulinic acid formation from glucose decomposition at high temperature was investigated. Glucose containing 1%, 3% or 5% H2SO4 was treated at 170℃ or 190℃. For the various experimental conditions assayed, the time-courses of glucose and glucose degradation products (including 5-hydroxymethylfurfural and levulinic acid) were established. These variables were cor-related with the reaction time based on the equations derived from a pseudo-homogeneous, first-order kinetic model, which provided a satisfactory interpretation of the experimental results. The set of kinetic parameters from regression of experimental data provided useful information for understanding the levulinic acid formation mechanism.展开更多
5-Aminolevulinic acid （ALA） is a common precursor for tetrapyrrole compounds in all kinds of organ isms and has wide applications in agriculture and medicines. In this study, a new strategy, i.e. short-term dissolve...5-Aminolevulinic acid （ALA） is a common precursor for tetrapyrrole compounds in all kinds of organ isms and has wide applications in agriculture and medicines. In this study, a new strategy, i.e. short-term dissolved oxygen （DO） shock during aerobic fermentation, was introduced to produce 5-aminolevulinic acid with a recombi-nant E. coli. Effects of duration time of DO shock operation on plasmid concentration, intracellular ALA synthase （ALAS） activity and ALA production were investigated in Erlenmeyer shake flasks. The results indicated that both ALAS activity and ALA yield were enhanced in an anaerobic operation of 45 rain in the early exponential phase during fermentation, while they decreased when the anaerobic operation time was further increased to 60 rain. The DO shock protocol was confirmed with the fed-batch fermentation in a 15 L fermenter and the ALA production achieved 9.4 g.L-1 （72 mmol.L-1）, which is the highest yield in the fermentation broth reported up to now.展开更多
The feeding method of propionic acid for production ofpoly(3-hydroxybutyrate-co-3-hydro xyvalerate) [P(3HB-co-3HV)] by fed-batch culture of Ralstoniaeutropha was optimized to achieve high cell density and high 3HV yie...The feeding method of propionic acid for production ofpoly(3-hydroxybutyrate-co-3-hydro xyvalerate) [P(3HB-co-3HV)] by fed-batch culture of Ralstoniaeutropha was optimized to achieve high cell density and high 3HV yield. Effects of different feedingstrategies of propionic acid on the production of P(3HB-co-3HV) were investigated. A decline ofspecific synthesis rate of copolymer and the yield of 3HV unit from propionic acid were observed dueto the propionic acid accumulation in culture broth when the feeding solution with highP/G(propionic acid to glucose) ratio was employed. It was further confirmed by controlling propionicacid concentration at a low level in the separate feeding of propionic acid. An optimal feedingstrategy was demonstrated to reduce the propionic acid accumulation. The cell concentration,P(3HB-co-3HV) productivity and 3HV unit fraction reached to 163.9kg·m^(-3), 1.8kg·m^(-3)·h^(-1),and 10.6%(by mass), respectively, resulting in a yield of 0.33g HV per g propionic acid.展开更多
文摘The shortage of petroleum has resulted in worldwide efforts to produce chemicals from renewable resources. Among these attempts, the possibility of producing acrylic acid from biomass has caught the eye of many researchers. Converting the carbohydrates first to lactic acid by fermentation and then dehydrating lactic acid to acrylic acid is hitherto the most effective way for producing acrylic acid from biomass. While the lactic acid fer- mentation has been commercialized since longer times, the dehydration process of lactic acid is still under development because of its low yield. Further efforts should be made before this process became economically feasible. Because of the existence of acrylic acid pathways in some microorganisms, strain improvement and metabolic engineering provides also a possibilitv to produce acrylic acid directly from biomass by fermentation.
基金Supported by the Natural Science Foundation of Henan Educational Committee (No.200510459056).
文摘Levulinic acid is a kind of new green platform chemical with wide application. The kinetics of levulinic acid formation from glucose decomposition at high temperature was investigated. Glucose containing 1%, 3% or 5% H2SO4 was treated at 170℃ or 190℃. For the various experimental conditions assayed, the time-courses of glucose and glucose degradation products (including 5-hydroxymethylfurfural and levulinic acid) were established. These variables were cor-related with the reaction time based on the equations derived from a pseudo-homogeneous, first-order kinetic model, which provided a satisfactory interpretation of the experimental results. The set of kinetic parameters from regression of experimental data provided useful information for understanding the levulinic acid formation mechanism.
基金Supported by the National Natural Science Foundation of China （20306026 and 20876141） and the National Basic Research program of China （2007CB707805）.
文摘5-Aminolevulinic acid （ALA） is a common precursor for tetrapyrrole compounds in all kinds of organ isms and has wide applications in agriculture and medicines. In this study, a new strategy, i.e. short-term dissolved oxygen （DO） shock during aerobic fermentation, was introduced to produce 5-aminolevulinic acid with a recombi-nant E. coli. Effects of duration time of DO shock operation on plasmid concentration, intracellular ALA synthase （ALAS） activity and ALA production were investigated in Erlenmeyer shake flasks. The results indicated that both ALAS activity and ALA yield were enhanced in an anaerobic operation of 45 rain in the early exponential phase during fermentation, while they decreased when the anaerobic operation time was further increased to 60 rain. The DO shock protocol was confirmed with the fed-batch fermentation in a 15 L fermenter and the ALA production achieved 9.4 g.L-1 （72 mmol.L-1）, which is the highest yield in the fermentation broth reported up to now.
文摘The feeding method of propionic acid for production ofpoly(3-hydroxybutyrate-co-3-hydro xyvalerate) [P(3HB-co-3HV)] by fed-batch culture of Ralstoniaeutropha was optimized to achieve high cell density and high 3HV yield. Effects of different feedingstrategies of propionic acid on the production of P(3HB-co-3HV) were investigated. A decline ofspecific synthesis rate of copolymer and the yield of 3HV unit from propionic acid were observed dueto the propionic acid accumulation in culture broth when the feeding solution with highP/G(propionic acid to glucose) ratio was employed. It was further confirmed by controlling propionicacid concentration at a low level in the separate feeding of propionic acid. An optimal feedingstrategy was demonstrated to reduce the propionic acid accumulation. The cell concentration,P(3HB-co-3HV) productivity and 3HV unit fraction reached to 163.9kg·m^(-3), 1.8kg·m^(-3)·h^(-1),and 10.6%(by mass), respectively, resulting in a yield of 0.33g HV per g propionic acid.
