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

Abstract

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, O2 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 (YBDO/Gly = 0.46 g/g, corresponding to 94% of the maximum theoretical yield; Ymt) and titer, while under anaerobic conditions, Citrobacter freundii NRRL-B 2645 and Enterobacter ludwigii FMCC-204 produced PDO (YPDO/Gly = 0.56 g/g, 93% of Ymt) and EtOH (YEtOH/Gly = 0.44 g/g, 88% of Ymt), 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 YBDO/Gly and the mean productivity value (PrBDO) 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 1596) 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.

Screening Bacterial Strains Capable of Producing 2,3-Butanediol: Process Optimization and High Diol Production by Klebsiella oxytoca FMCC-197

“…This is indeed somehow paradoxical and surprising, given that the fermentation of BDO is practically mostly an anaerobic/microaerophilic process. Nevertheless, in full agreement with many reports that have appeared in the literature [5,6,[11][12][13][14], the current investigation provides sufficient evidence for the biosynthesis and the subsequent remarkable production of BDO under full aerobic conditions, suggesting that a part of the NADH 2 co-enzymes that had been produced through the glycolysis pathway are recycled through the sugar pathway that yields → BDO, while simultaneously another part of the intracellular pool of these NADH 2 co-enzymes is recycled through the oxidative phosphorylation pathway, indicating simultaneous oxidative and fermentative features realized under fully aerobic conditions in the presently used strain. Table 4.…”

“…The microbial species that are predominately referred to in the literature for their ability to produce BDO in significant quantities belong mostly to the bacterial genera Klebsiella, Enterobacter, Bacillus, and Serratia [11][12][13]. Additionally, various strains of the species Lactobacillus and Lactococcus have the potential to produce BDO in remarkable concentrations [14].…”