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.

Improved ethanol tolerance and ethanol production from glycerol in a streptomycin-resistant Klebsiella variicola mutant obtained by ribosome engineering.

To improve the ethanol tolerance of the Klebsiella variicola strain TB-83, we obtained the streptomycin-resistant, ethanol-tolerant mutant strain TB-83D by a ribosome engineering approach. Strain TB-83D was able to grow in the presence of 7% (v/v) ethanol and it showed higher ethanol production than strain TB-83. Examination of various culture conditions revealed that yeast extract was essential for ethanol production and bacterial growth.

Ethanol production from glycerol-containing biodiesel waste by Klebsiella variicola shows maximum productivity under alkaline conditions.

Biodiesel fuel (BDF) waste contains large amounts of crude glycerol as a by-product, and has a high alkaline pH. With regard to microbial conversion of ethanol from BDF-derived glycerol, bacteria that can produce ethanol at alkaline pH have not been reported to date. Isolation of bacteria that shows maximum productivity under alkaline conditions is essential to effective production of ethanol from BDF-derived glycerol.