Utilization of renewable and low-cost lignocellulosic wastes has received major focus in industrial lactic acid production. The use of high solid loadings in biomass pretreatment potentially offers advantages over low solid loadings including higher lactic acid concentration with decreased production and capital costs. In this study, an isolated Enterococcus faecalis SI with optimal temperature 42 °C was used to produce optically pure L-lactic acid (> 99%) from enzyme-saccharified hydrolysates of acid-impregnated steam explosion (AISE)-treated plywood chips. The L-lactic acid production increased by 10% at 5 L scale compared to the similar fermentation scheme reported by Wee et al. The fermentation with a high solid loading of 20% and 35% (w/v) AISE-pretreated plywood chips had been successfully scaled up to process development unit scale (100 L) and pilot scale (9 m), respectively. This is the first report of pilot-scale lignocellulosic lactic acid fermentation by E. faecalis with high lactic acid titer (nearly 92 g L) and yield (0.97 kg kg). Therefore, large-scale L-lactic acid production by E. faecalis SI shows the potential application for industries.
BACKGROUND: Bioethanol is an attractive alternative fuel because it is less carbon-intensive than oil and is also a renewable bio-based energy source. The aim of this study is to present a mathematical modeling approach in order to describe the simultaneous saccharification and fermentation process of the yeast Saccharomyces cerevisiae YPB-G for the production of bioethanol using starch.RESULTS: An unstructured model was proposed for model parameters that are independent of initial operating conditions, but have a highly predictive capability that can be used in process optimization and control. The predictions of the proposed models were compared with experimental data and against the results of other models presented in the literature.
CONCLUSION:A technique of gradually expanding the search domain combined with a genetic algorithm was proposed to successfully speed up the optimization computation of parameter estimation. Compared with an earlier model presented in the literature, the proposed model shows more versatility with fewer numbers of parameters and fixed values of parameters, and provides a satisfactory prediction capability. The proposed model was used to investigate the process optimization of batch culture. Numerical results may provide various process alternatives for planning the productivity of bioethanol.Figure 5. Performance curves of batch systems for initial biomass 1.0 g L -1 : (a) ethanol productivity, (b) ethanol concentration at the end time, (c) optimal starch concentration, (d) optimal completion time.wileyonlinelibrary.com/jctb
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