Efficient production of ethanol from crude glycerol by a Klebsiella pneumoniae mutant strain

A mutant strain of Klebsiella pneumoniae, termed GEM 167, was obtained by gamma irradiation, in which glycerol metabolism was dramatically affected on exposure to gamma rays. Levels of metabolites of the glycerol reductive pathway, 1,3-propanediol (1,3-PD) and 3-hydroxypropionic acid (3-HP), were decreased in the GEM167 strain compared to a control strain, whereas the levels of metabolites derived from the oxidative pathway, 2,3-butanediol (2,3-BD), ethanol, lactate, and succinate, were increased. Notably, ethanol production from glycerol was greatly enhanced upon fermentation by the mutant strain, to a maximum production level of 21.5 g/l, with a productivity of 0.93 g/l/h. Ethanol production level was further improved to 25.0 g/l upon overexpression of Zymomonas mobilis pdc and adhll genes encoding pyruvate decarboxylase (Pdc) and aldehyde dehydrogenase (Adh), respectively in the mutant strain GEM167. (C) 2010 Elsevier Ltd. All rights reserved.