Preliminary study of bioethanol production by Saccharomyces cerevisiae BTCC12 utilizing hydrolysis products of Dioscorea hispida tubers

Abstract

Dioscorea hispida is an underutilised plant despite its high carbohydrate content. This study used D. hispida starch as the raw material for bioethanol production by employing Separated Hydrolysis Fermentation (SHF) technique. Initially, the starch was used as the sole carbon source for Aspergillus awamori KT-11 to produce amylases. The optimum enzyme activity (7.4 U/ml) was observed at 96 h fermentation. The enzymes were further used to hydrolyse D. hispida starch. The optimum condition for the hydrolysis was achieved at 6 h when using a mixture of starch and enzyme with a ratio of 1:6 (w/v). Thin-layer chromatography results showed that the main hydrolysis product was glucose. The hydrolysates were then used by Saccharomyces cerevisiae BTCC12 as the medium for bioethanol fermentation. HPLC analysis showed that the optimum ethanol concentration was 0.37 g/L after 6 h fermentation while the reducing sugar concentration was only 2.9% of the initial. The results provide a solid basis for further studies to optimise bioethanol fermentation utilising D. hispida as the substrate.