1,3-propanediol production by fermentation: An interesting way to valorize glycerin from the ester and ethanol industries

Glycerol is the main by-product from the conversion of agricultural crops into non-alimentary products such as ester and bioethanol. Its microbiological transformation to 1,3-propanediol constitutes a recent approach. The bioproduction of 1,3-propanediol by bacterial species Klebsiella pneumoniae, Citrobacter freundii, Enterobacter agglomerans and Clostridium butyricum have been investigated by batch fermentation and compared at low and high glycerol contents. An important metabolic flexibility was observed with the enterobacteria in contrast to C. butyricum. Fermentation of glycerol by the enterobacterial species revealed the occurrence of an inhibitory phenomenon. It was assigned to the accumulation in the fermentation medium of a strongly inhibitory compound, 3-hydroxypropionaldehyde, the only intermediate of the 1,3-propanediol metabolic pathway. This phenomenon was shown to significantly decrease the biological activities and to be dependent on the culture pH conditions. It was not observed with C. butyricum. By comparing the efficiency of the fermentation among the four bacteria, C. butyricum was chosen for an applied study consisting of the bioconversion of glycerol containing industrial wastewaters. With glycerin coming from the ester production and from wine stillage, a high efficiency of conversion to 1,3-propanediol was observed. The 1,3-propanediol produced was purified by liquid/liquid extraction with a recovery yield about 100%. (C) 1998 Elsevier Science B.V.