Dry yeast cells （DYC） were used as a cheap nitrogen source to replace expensive yeast extract （YE） for L-lactic acid production by thermophilic Bacillus coagulans. Cassava starch （200 g. L1） was converted to L-l...Dry yeast cells （DYC） were used as a cheap nitrogen source to replace expensive yeast extract （YE） for L-lactic acid production by thermophilic Bacillus coagulans. Cassava starch （200 g. L1） was converted to L-lactic acid by simultaneous saccharification and fermentation using Bacillus coagulans WCP10-4 at 50℃ in the presence of 20g·L-1 of DYC, giving 148.1 g·L-1 of L- lactic acid at 27 h with a productivity of 5.5 g·L-1·h-1 and a yield of 92%. In contrast, 154.4 g·L-1 of lactic acid was produced at 24 h with a productivity of 6.4 g·L-1. hl and a yield of 96% when equal amount of YE was used under the same conditions. Use of pre-autolyzed DYC at 50℃ for overnight slightly improved the lactic acid titer （154.5g·L-1） and productivity （7.7g·L-1·h-1） but gave the same yield （96%）.展开更多
Pseudomonas putida KT217 produces medium-chain-length polyhydroxyalkanoate(mcl-PHA)that is of commercial interest as a biodegradable plastic.To reduce PHA production costs,a less expensive medium to grow P.putida KT21...Pseudomonas putida KT217 produces medium-chain-length polyhydroxyalkanoate(mcl-PHA)that is of commercial interest as a biodegradable plastic.To reduce PHA production costs,a less expensive medium to grow P.putida KT217 to a high cell dry weight(CDW)was developed.P.putida KT217 was grown in aerated shake flasks on a condensed corn solubles(CCS)based medium that provided several organic acids and carbohydrates that were utilized for growth.The medium was prepared by adding various amounts of fresh CCS(100-600 g/L,or 34.9-209.4 g/L dry basis)to water and then centrifuging and filtering.The CCS permeate media contained dry matter levels of 28.8-164.9 g/L.The CCS permeate medium containing 108.4 g/L solids produced approximately 6 g CDW/L,at a growth rate of 1.03 per hour,and maximum cell population of 4×109 CFU/mL.Because CCS is low in nitrogen,ammonium hydroxide was added at a level of 1.73 g/L,and this significantly increased the CDW(>20 g/L)produced in an aerated bioreactor.Therefore,a nitrogen supplemented CCS medium could provide a cheap source of nutrients for production of P.putida KT217 and PHA.展开更多
文摘Dry yeast cells （DYC） were used as a cheap nitrogen source to replace expensive yeast extract （YE） for L-lactic acid production by thermophilic Bacillus coagulans. Cassava starch （200 g. L1） was converted to L-lactic acid by simultaneous saccharification and fermentation using Bacillus coagulans WCP10-4 at 50℃ in the presence of 20g·L-1 of DYC, giving 148.1 g·L-1 of L- lactic acid at 27 h with a productivity of 5.5 g·L-1·h-1 and a yield of 92%. In contrast, 154.4 g·L-1 of lactic acid was produced at 24 h with a productivity of 6.4 g·L-1. hl and a yield of 96% when equal amount of YE was used under the same conditions. Use of pre-autolyzed DYC at 50℃ for overnight slightly improved the lactic acid titer （154.5g·L-1） and productivity （7.7g·L-1·h-1） but gave the same yield （96%）.
基金funding provided by the South Dakota Corn Utilization Council.
文摘Pseudomonas putida KT217 produces medium-chain-length polyhydroxyalkanoate(mcl-PHA)that is of commercial interest as a biodegradable plastic.To reduce PHA production costs,a less expensive medium to grow P.putida KT217 to a high cell dry weight(CDW)was developed.P.putida KT217 was grown in aerated shake flasks on a condensed corn solubles(CCS)based medium that provided several organic acids and carbohydrates that were utilized for growth.The medium was prepared by adding various amounts of fresh CCS(100-600 g/L,or 34.9-209.4 g/L dry basis)to water and then centrifuging and filtering.The CCS permeate media contained dry matter levels of 28.8-164.9 g/L.The CCS permeate medium containing 108.4 g/L solids produced approximately 6 g CDW/L,at a growth rate of 1.03 per hour,and maximum cell population of 4×109 CFU/mL.Because CCS is low in nitrogen,ammonium hydroxide was added at a level of 1.73 g/L,and this significantly increased the CDW(>20 g/L)produced in an aerated bioreactor.Therefore,a nitrogen supplemented CCS medium could provide a cheap source of nutrients for production of P.putida KT217 and PHA.
