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Screening of New Industrially Important Bacterial Strains for 1,3-Propanediol, 2,3-Butanediol and Ethanol Production through Biodiesel-Derived Glycerol Fermentations
oleh: Dimitris Karayannis, Gabriel Vasilakis, Ioannis Charisteidis, Alexandros Litinas, Eugenia Manolopoulou, Effie Tsakalidou, Seraphim Papanikolaou
Format: | Article |
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Diterbitkan: | MDPI AG 2023-05-01 |
Deskripsi
A study on the ability of new microbial strains to assimilate biodiesel-derived glycerol at low purity (75% <i>w</i>/<i>w</i>) 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<sub>2</sub> 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, <i>Klebsiella oxytoca</i> ACA-DC 1581 produced BDO in high yield (Y<sub>BDO/Gly</sub> = 0.46 g/g, corresponding to 94% of the maximum theoretical yield; Y<sub>mt</sub>) and titer, while under anaerobic conditions, <i>Citrobacter freundii</i> NRRL-B 2645 and <i>Enterobacter ludwigii</i> FMCC-204 produced PDO (Y<sub>PDO/Gly</sub> = 0.56 g/g, 93% of Y<sub>mt</sub>) and EtOH (Y<sub>EtOH/Gly</sub> = 0.44 g/g, 88% of Y<sub>mt</sub>), respectively. In the case of <i>C. freundii</i>, 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 <i>K. oxytoca</i>, the BDO maximum titer reached almost 70 g/L, the Y<sub>BDO/Gly</sub> and the mean productivity value (Pr<sub>BDO</sub>) 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 (<i>K. oxytoca</i>) 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 <i>Hafnia alvei</i> (<i>viz</i>., <i>Hafnia alvei</i> 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.