Glycerol has become an inexpensive and abundant carbon source due to its generation as inevitable by-product of biofuels production. Given the high degree of reduction of carbon in glycerol, fuels and reduced chemicals could be produced from glycerol at yields higher than those obtained from common sugars. Fully realizing this potential, however, requires the metabolism of glycerol in the absence of external electron acceptors (i.e., fermentative metabolism). Unfortunately, only a small group of microorganisms, most of which are not amenable to industrial applications, was known to be capable of fermentative utilization of glycerol prior to our work. In these organisms, the ability to synthesize 1,3-propanediol (1,3-PDO) has long been considered the metabolic property that enables to ferment glycerol. For example, Escherichia coli and Saccharomyces cerevisiae, workhorses of modern biotechnology, do not have the capacity to synthesize 1,3-PDO and therefore have been deemed unable to conduct glycerol fermentation.
Following our recent discovery that the previous view was incorrect and that although E. coli cannot synthesize 1,3-PDO it can indeed ferment glycerol in the absence of external electron acceptors, we have engineered this organism for the conversion of glycerol to fuels and chemicals. Several biocatalysts have been developed for the production of ethanol, hydrogen, formate, succinate, lactate, and 3- and 4-carbon diols from glycerol-rich streams generated during biofuels production (e.g. crude glycerol, thin stillage). This paper will include the discussion of our latest work related to the harnessing of microbial glycerol fermentation for the production of fuels and chemicals.