Characterization of Hydrogen Production by Escherichia coli Wild-type and Mutants of Hydrogenases Utilizing Xylose as Fermentation Substrate
2019
Poladyan, Anna | Trchounian, Armen
Xylose, one of the most common sugars derived from lignocellulosic material, can be fermented by bacteria. Escherichia coli uses natural sugars to produce biomass and H₂. The latter can be formed from the formate via formate hydrolysis (FHL) during the fermentation of xylose or glucose; [Ni-Fe]-hydrogenase (Hyd) is involved in H₂ formation. The growth, H₂ production characteristics of E. coli BW25113 (wild-type), and ΔhyaB, ΔhybC, ΔhycE, or ΔhyfG mutant strains with deletions of catalytic subunits of Hyd-1 to Hyd-4, respectively, were monitored with addition of 0, 0.5, to 1% xylose on peptone and minimal salt-based mediums, pH 5.5 and pH 7.5. At pH 5.5, with the growth of bacteria on both media, H₂ produced in the early logarithmic phase (1.40–0.02 mmol H₂ L⁻¹), whereas at pH 7.5 it is noticeably delayed. Results showed that during the fermentation of xylose, Hyd-3 and Hyd-4 are important for both bacterial growth and production of H₂, mainly at pH 5.5. In addition, high xylose concentrations can stimulate the activity of the Hyd-1 enzyme during bacterial growth at pH 7.5. These results are new and important for developing advanced H₂ production technologies using xylose as a feedstock.
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