L-(+)-Lactic acid production from corncob hydrolysate as a cheap carbohydrate source by fed-batch fermentation of Rhizopus oryzaeHZS6 was studied. After 96 h of fermentation in a 5 L fermentor, the final concentration...L-(+)-Lactic acid production from corncob hydrolysate as a cheap carbohydrate source by fed-batch fermentation of Rhizopus oryzaeHZS6 was studied. After 96 h of fermentation in a 5 L fermentor, the final concentration of ammonium L-(+)-lactate, average productivity(based on initial xylose concentration) and maximum dry cell weight were 132.4 g/L, 1.38 g/(L·h), and 8.9 g/L respectively. The optical purity of L-(+)-lactate was 98.8%.展开更多
In this paper,a novel fuzzy neural network model,in which an adjustable fuzzy sub-space was designed by uniform design,has been established and used in fed-batch yeast fermentationas an example.A brand-new optimizatio...In this paper,a novel fuzzy neural network model,in which an adjustable fuzzy sub-space was designed by uniform design,has been established and used in fed-batch yeast fermentationas an example.A brand-new optimization sub-network with special structure has been built andgenetic algorithm,guaranteeing the optimization in overall space,is introduced for the feed rateoptimization.On the basis of the model network,the optimal substrate concentration and theoptimal amount of fed-batch at different periods have been studied,aided with the optimizationnetwork and the genetic algorithm separately.The above results can be used as a basis for theestablishment of a fuzzy neural network controller.展开更多
As a kind of aerobic bacteria, Saccharopolyspora spinosa exhibits a high demand for oxygen. In the fermentation process, the methods of increasing ventilation and improving agitation speed are usually adopted to achie...As a kind of aerobic bacteria, Saccharopolyspora spinosa exhibits a high demand for oxygen. In the fermentation process, the methods of increasing ventilation and improving agitation speed are usually adopted to achieve higher values of dissolved oxygen. These methods decrease the efficiency of spinosad biosynthesis.In this study, an improved reactor was designed to solve these problems. The exhaust gas reflux device, impellers,and baffles were improved. Furthermore, we established the kinetic models for the cell growth, substrate consumption and spinosad generation in batch fermentation process. The simulation results were in good agreement with the experimental data. Spinosad production reached 583.86 mg/L after employing the suitable feeding strategy by fed-batch fermentation in the improved reactor, whereas it was only 157.01 mg/L before optimization. The method described can provide insight to strengthen spinosad production and can be extended to the culturing process of filamentous aerobic bacteria.展开更多
An alkalophilc and thermophilic Bacillus sp. BHA that produced a thermostable alkaline protease was isolated from decaying protein substrates. The isolate was found to grow in pH range 7 - 11 with an optimum pH 9.0 an...An alkalophilc and thermophilic Bacillus sp. BHA that produced a thermostable alkaline protease was isolated from decaying protein substrates. The isolate was found to grow in pH range 7 - 11 with an optimum pH 9.0 and temperature up to 55℃. The activity of alkaline protease of Bacillus sp. BHA (68.98 APU/ml) was found higher than the standard strains of Bacillus amyloliquefaciens MTCC 610 (8.98 APU/ml) and Bacillus subtilis MTCC 8349 (12.14 APU/ml, used in this study, and was comparable (68.98 APU/ml, equivalent to 30.38 APU/mg) to the activity of the commercially produced standard protease procured from Novo Nordisk, Denmark (30.35 APU/mg). Hence, the proteolytic activity produced by this isolate was further investigated in batch and fed-batch process. Sucrose was the best carbon source for the production of protease activity by that isolate. Different organic nitrogen sources (casein, peptone and beef extract) at 1% (w/v) with varying levels of sucrose (1% - 4% w/v) initially repress enzyme synthesis. The duration and extent of repression decreased with increased concentration of sucrose. Maximum protease activity was found in basal medium with 4% (w/v) sucrose and 1% (w/v) yeast extract. Yeast-extract was thought to be an inducer of enzyme synthesis. Further, the basal medium was unique with respect to the enzyme production, as protease production was growth associated with the peak enzyme production being detected at the time of maximum growth. Interestingly, a rise in 34.2% (104.86 APU/ml) of protease activity was detected at incubation temperature of 50℃ and when culture filtrate was assayed at 60℃, signifying a high temperature stability of the produced protease by this isolate. Additional studies on the enzyme characterization were resulted in recognition of highly significant properties of the activity towards casein at pH 9.0 and stability at high temperature with retention of 96% the enzyme activity at 60℃. The parametric study under feed intervals had enabled improvement in the maximum protease activities attainable from batch cultures in excess of 21.78% and 26.32% via two feeding strategies. A small continual increase in enzyme activity (132.46 APU/ml during 24 h - 120 h) and enhancement in protease production in excess of 36.84% was observed by fed-batch process than the batch experiment.展开更多
基金Partially suppored by a grant for the U K DTI- China MOST Collaborative Research
文摘L-(+)-Lactic acid production from corncob hydrolysate as a cheap carbohydrate source by fed-batch fermentation of Rhizopus oryzaeHZS6 was studied. After 96 h of fermentation in a 5 L fermentor, the final concentration of ammonium L-(+)-lactate, average productivity(based on initial xylose concentration) and maximum dry cell weight were 132.4 g/L, 1.38 g/(L·h), and 8.9 g/L respectively. The optical purity of L-(+)-lactate was 98.8%.
基金Supported by the National Natural Science Foundation of China,No.29476248 and Trans-Century Training Program Foundation for the Talents by the State Education Commission.
文摘In this paper,a novel fuzzy neural network model,in which an adjustable fuzzy sub-space was designed by uniform design,has been established and used in fed-batch yeast fermentationas an example.A brand-new optimization sub-network with special structure has been built andgenetic algorithm,guaranteeing the optimization in overall space,is introduced for the feed rateoptimization.On the basis of the model network,the optimal substrate concentration and theoptimal amount of fed-batch at different periods have been studied,aided with the optimizationnetwork and the genetic algorithm separately.The above results can be used as a basis for theestablishment of a fuzzy neural network controller.
基金supported by the National Natural Science Foundation of China(No.21076148 and No.31270087)Plan of Tianjin Science and Technology Support(11ZCKFSY0100)
文摘As a kind of aerobic bacteria, Saccharopolyspora spinosa exhibits a high demand for oxygen. In the fermentation process, the methods of increasing ventilation and improving agitation speed are usually adopted to achieve higher values of dissolved oxygen. These methods decrease the efficiency of spinosad biosynthesis.In this study, an improved reactor was designed to solve these problems. The exhaust gas reflux device, impellers,and baffles were improved. Furthermore, we established the kinetic models for the cell growth, substrate consumption and spinosad generation in batch fermentation process. The simulation results were in good agreement with the experimental data. Spinosad production reached 583.86 mg/L after employing the suitable feeding strategy by fed-batch fermentation in the improved reactor, whereas it was only 157.01 mg/L before optimization. The method described can provide insight to strengthen spinosad production and can be extended to the culturing process of filamentous aerobic bacteria.
文摘An alkalophilc and thermophilic Bacillus sp. BHA that produced a thermostable alkaline protease was isolated from decaying protein substrates. The isolate was found to grow in pH range 7 - 11 with an optimum pH 9.0 and temperature up to 55℃. The activity of alkaline protease of Bacillus sp. BHA (68.98 APU/ml) was found higher than the standard strains of Bacillus amyloliquefaciens MTCC 610 (8.98 APU/ml) and Bacillus subtilis MTCC 8349 (12.14 APU/ml, used in this study, and was comparable (68.98 APU/ml, equivalent to 30.38 APU/mg) to the activity of the commercially produced standard protease procured from Novo Nordisk, Denmark (30.35 APU/mg). Hence, the proteolytic activity produced by this isolate was further investigated in batch and fed-batch process. Sucrose was the best carbon source for the production of protease activity by that isolate. Different organic nitrogen sources (casein, peptone and beef extract) at 1% (w/v) with varying levels of sucrose (1% - 4% w/v) initially repress enzyme synthesis. The duration and extent of repression decreased with increased concentration of sucrose. Maximum protease activity was found in basal medium with 4% (w/v) sucrose and 1% (w/v) yeast extract. Yeast-extract was thought to be an inducer of enzyme synthesis. Further, the basal medium was unique with respect to the enzyme production, as protease production was growth associated with the peak enzyme production being detected at the time of maximum growth. Interestingly, a rise in 34.2% (104.86 APU/ml) of protease activity was detected at incubation temperature of 50℃ and when culture filtrate was assayed at 60℃, signifying a high temperature stability of the produced protease by this isolate. Additional studies on the enzyme characterization were resulted in recognition of highly significant properties of the activity towards casein at pH 9.0 and stability at high temperature with retention of 96% the enzyme activity at 60℃. The parametric study under feed intervals had enabled improvement in the maximum protease activities attainable from batch cultures in excess of 21.78% and 26.32% via two feeding strategies. A small continual increase in enzyme activity (132.46 APU/ml during 24 h - 120 h) and enhancement in protease production in excess of 36.84% was observed by fed-batch process than the batch experiment.
