Microbial Conversion of Glycerol Into 1,3-Propanediol by Fermentation: Review of Fundamentals and Operational Strategies.

Over the past decades, biodiesel production has sharply increased worldwide and has led to an overproduction of glycerol, as by-product. Therefore, glycerol is not only produced at low cost with a wide availability but is also a versatile precursor of useful value-added chemicals such as1,3-propanediol. At an industrial scale, glycerol conversion into 1,3-propanediol is almost entirely carried out by fermentation processes as they have shown the best economic and environmental performances. The aim of this article is to provide an up-to-date state of the art on the fundamentals and fermentation process strategies for the microbial conversion of glycerol into 1,3-propanediol. Glycerol fermentation metabolism is detailed and strategies concerning microbial inoculum (i.e., pure cultures of natural or genetically modified strains vs. mixed cultures or artificial consortia), process configuration (i.e., batch, fed-batch and continuous reactors, biomass immobilisation) and related operational parameters (i.e., temperature, pH, oxido-reduction potential) are discussed for the optimisation of 1,3-propanediol production by fermentation.