| Summary: | 碩士 === 元培科技大學 === 食品科學研究所 === 100 === Abstract
Co-cultures of P. stipitis and S. cerevisiae in the synthetic and cellulosic hydrolysate-based media for the production of bioethanol were studied. Firstly, glucose was used as the sole carbon source for ethanol fermentation in a 5-L fermentor. The ethanol yields were 102 g/l when the initial glucose concentrations in the batch culture were 200 g/l. However, when the initial glucose concentration reached 260 g/l, ethanol yields (115.1 g/l) were not significantly increased, suggesting that a considerable inhibitory effect of substrate had occurred. The initial glucose concentrations in the fed-batch culture were 180 g/l and an addition of 40 g/l glucose after 1 and 2 days of incubation, respectively. The results showed higher concentrations of ethanol (130.1 g/l) were produced. In the second part, the effect of various initial concentrations of glucose and ratio of microbial inoculum in the synthetic media with co-cultures of P. stipitis and S. cerevisiae were investigated. The optimum initial concentrations of glucose and xylose in the media were 40 g/l and 20 g/l, respectively. Additionally, the ethanol yields were increased with the raise of the initial glucose concentration; however xylose consumption rate was not significantly increased. Furthermore, the effect of various ratio of microbial inoculum on the ethanol concentration and xylose consumption rate was not significant. The third part of the study is focused on the bioethanol production using corncob hydrolysate as the substrate in the media. After corncob was pretreated by sulfuric acid and autoclaved, bioethanol production of the batch and fed-batch co-cultures of P. stipitis and S. cerevisiae in the corncob hydrolysate-based media was studied. The yeast biomass, ethanol yields and ethanol conversion rate was 8.7 g/l, 31.2 g/l and 48.1%, respectively, in the batch cultures using the media containing 60 g/l glucose and 8.4 g/l xylose. Furthermore, the fed-batch cultures were performed using the media containing initial 60 g/l glucose and 6.9 g/l xylose and fed with 20 g/l glucose after 2 days of incubation. The yeast biomass, ethanol yields and ethanol conversion rate was increased to 12.1 g/l, 45.2 g/l and 52.3%, respectively. The ethanol yields and ethanol conversion rate of fed-batch cultures in the corncob hydrolysate-based media were higher than those were in batch cultures. The ethanol yields and ethanol conversion rate cultured in the fermentor were also higher than those of the cultures in conical flask. Based on the results, optimization and scale-up of fed-batch fermentation using corncob hydrolysate for the bioethanol production could be developed to make the process industrially feasible.
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