Screening of New Industrially Important Bacterial Strains for 1,3-Propanediol, 2,3-Butanediol and Ethanol Production through Biodiesel-Derived Glycerol Fermentations.

A study on the ability of new microbial strains to assimilate biodiesel-derived glycerol at low purity (75% w / w ) and produce extra-cellular platform chemical compounds of major interest was carried out. After screening several bacterial strains under different fermentation conditions (e.g., pH, O 2 availability, glycerol purity), three of the screened strains stood out for their high potential to produce valued-added products such as 2,3-butanediol (BDO), 1,3-propanediol (PDO) and ethanol (EtOH). The results indicate that under aerobic conditions, Klebsiella oxytoca ACA-DC 1581 produced BDO in high yield (Y BDO/Gly = 0.46 g/g, corresponding to 94% of the maximum theoretical yield; Y mt ) and titer, while under anaerobic conditions, Citrobacter freundii NRRL-B 2645 and Enterobacter ludwigii FMCC-204 produced PDO (Y PDO/Gly = 0.56 g/g, 93% of Y mt ) and EtOH (Y EtOH/Gly = 0.44 g/g, 88% of Y mt ), respectively. In the case of C. freundii , the regulation of pH proved to be mandatory, due to lactic acid production and a subsequent drop of pH that resulted in fermentation ceasing. In the fed-batch culture of K. oxytoca , the BDO maximum titer reached almost 70 g/L, the Y BDO/Gly and the mean productivity value (Pr BDO ) were 0.47 g/g and 0.4 g/L/h, respectively, while no optimization was imposed. The final BDO production obtained by this wild strain ( K. oxytoca ) is among the highest in the international literature, although the bioprocess requires optimization in terms of productivity and total cost. In addition, for the first time in the literature, a strain from the species Hafnia alvei ( viz ., Hafnia alvei ACA-DC 1196) was reported as a potential BDO producer. The strains as well as the methodology proposed in this study can contribute to the development of a biorefinery that complements the manufacture of biofuels with high-value biobased chemicals.