Statistical optimization of bioethanol production from waste bread hydrolysate

A recent trend in sustainable bioethanol production is the use of agricultural waste or food waste as an inexpensive and the most available feedstock. Bread waste is the major food waste that could be successfully used for the production of bioethanol. The aim of this study was to optimize ethanol production by the response surface methodology (RSM) using waste bread hydrolysate. Waste bread hydrolysate was obtained using crude hydrolytic enzymes that produce bacterial isolate Hymenobacter sp. CKS3. The influence of time of fermentation (24-72 h) and waste brewer's yeast inoculum (1-4 %) on ethanol production was studied. The optimal conditions, obtained by central composite design (CCD), were 48.6 h of fermentation and 2.85 % of inoculum. Under these conditions, a maximum of 2.06 % of ethanol concentration was reached. The obtained ethanol concentration was in good correlation, coefficient of 0.858, with yeast cell yield. The results obtained in this study imply that waste bread hydrolysate could be used as a biomass source for biofuel production with multiple benefits relating to environmental protection, reduction of production costs, and saving fossil fuels