Investigation of Proton-Potassium Exchange During Fermentation of Glycerol by Bacteria Escherichia Coli at Alkaline and Acidic pH

Abstract

Production of molecular hydrogen (H2) by bacteria from a variety of renewable, cheap and abundant carbon sources is a developing new area of technology. Recently it has been shown that bacteria Escherichia coli is able to ferment glycerol and produce H2 via formate hydrogen lyase (FHL) system probably (1). It was demonstrated that in E. coli during fermentation of glucose depending of medium pH H2 produces via two forms of FHL-1 and FHL-2, constituted by formate dehydrogenase H and hydrogenase 3 (H3) or hydrogenase 4 (H4): at alkaline pH FHL-2 was shown to relate with the proton translocating F0F1-ATPase and potassium uptake TrkA system (2).In this study it's shown that at acidic (pH 5.5) and alkaline (pH 7.5) medium in E. coli wild typefermenting glycerol protons expelled via F0F1-ATPase with low rate compared with the glucose fermentation. The potassium uptake was very low. During fermentation of glycerol at alkaline pH H+ extrusion was stimulated in ΔhyfG or ΔfhlA (with defective H4 or activator of FHL, respectively)and not markedly changed in ΔhyaB or ΔhybC mutants (with defective H1 or H2). The H+ extrusion was almost the same in all these mutants at acidic pH. The results indicate that at alkaline pH when F0F1-ATPase activity is low H3 or H4 but not other hydrogenases may participate in the H+ extrusion or have proton translocating ability.1. Dharmadi,Y., Murarka, A. and Gonzalez, R. (2006) Biotechnol. Bioeng. 94, 821-828.2. Poladyan, A. and Trchounian, A. (2009) In Bacterial Membranes. Ed. A. Trchounian, Research Signpost, Kerala (India), pp.197-231.