Potential use of methane fermentation digested slurry as a low-cost, environmentally-friendly nutrient for bioethanol production from crude glycerol by Klebsiella variicola TB-83D

A methane fermentation digested slurry (MFDS) was evaluated as a substitute for the commercial nutrient, yeast extract (YE), in ethanol production from glycerol by Klebsiella variicola strain TB-83D. In pH-controlled fed-batch cultures, partial replacement of YE by MFDS did not reduce ethanol productivity significantly. However, non-sterilized MFDS had negative effects on glycerol fermentation by this strain. Although ethanol production decreased when YE was completely replaced by sterilized MFDS, the use of crude glycerol and sterilized MFDS achieved a yield of 14.6 g/L ethanol. This is the first study to report the use of MFDS as the sole nutrient for ethanol production from glycerol, which contributes to the development of a low-cost glycerol biorefinery derived from the biodiesel fuel industry.