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Sequential acid and enzymatic hydrolysis in situ and bioethanol production from Gracilaria biomass

Wu, Fang-Chen, Wu, Jane-Yii, Liao, Yi-Jyun, Wang, Man-Ying, Shih, Ing-Lung
Bioresource technology 2014 v.156 pp. 123-131
Gracilaria, Saccharomyces cerevisiae, batch fermentation, bioethanol, biomass, biorefining, enzymatic hydrolysis, ethanol, ethanol production, feedstocks, galactose, glucose, hydrolysates, saccharification
Gracilaria sp., a red alga, was used as a feedstock for the production of bioethanol. Saccharification of Gracilaria sp. by sequential acid and enzyme hydrolysis in situ produced a high quality hydrolysate that ensured its fermentability to produce ethanol. The optimal saccharification process resulted in total 11.85g/L (59.26%) of glucose and galactose, Saccharomyces cerevisiae Wu-Y2 showed a good performance on co-fermentability of glucose and galactose released in the hydrolysate from Gracilaria sp. The final ethanol concentrations of 4.72g/L (0.48g/g sugar consumed; 94% conversion efficiency) and the ethanol productivity 4.93g/L/d were achieved. 1g of dry Gracilaria can be converted to 0.236g (23.6%) of bioethanol via the processes developed. Efficient alcohol production by immobilized S. cerevisiae Wu-Y2 in batch and repeated batch fermentation was also demonstrated. The findings of this study revealed that Gracilaria sp. can be a potential feedstock in biorefinery for ethanol production.