Ethanol Production from Reused Liquid Stillage

Stillage, a liquid waste remaining after ethanol distillation, was collected and characterized. The liquid stillage contained reducing sugars (fructose and glucose) and volatile fatty acids including acetic acid, propionic acid and butyric acid. 1.48 g/L of reducing sugar was found in raw stillage. Therefore, the stillage was able to be utilized as a substrate for ethanol production. The production of ethanol from stillage was done using different glucose concentrations [ 10, 20, 40 and control (raw material, no glucose addition)] and different microorganisms including Saccharomyces cerevisiae and Enterobacter aerogenes. In addition, the mix-culture of S. cerevisiae and E. aerogenes for ethanol production was also evaluated. The process was done under batch fermentation at 35 degrees C, 100 rpm for 96 h. The results showed that mix-culture between S. cerevisiae and E. aerogenes yield the highest ethanol (1.762 g ethanol/g sugar) after 72 h of cultivation using the raw stillage (non-glucose addition) as a substrate. (C) 2015 The Authors. Published by Elsevier Ltd.