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Presentation Abstract Abstract Title:

Effect of Different Carbon Sources Mixture on Hydrogen Production by Escherichia coli at Slightly Alkaline pH

Author Block:

K. Trchounian, A. Trchounian; Yerevan State Univ., Yerevan, Armenia

Presentation 239 Number: Poster Board Number:

239

Keywords:

fermentation,H2 production,Escherichia coli

Abstract:

Escherichia coli performs mixed acid fermentation. Among fermentation end products molecular hydrogen (H2) gas is generated. H2 is produced via special enzymes named hydrogenases (Hyd) [1]. E. coli encodes four [Ni-Fe] Hyd enzymes having different role in H2 production and oxidation during sugar (glucose) and/or glycerol fermentation that is dependent on pH [1]. H2 evolving activity by E. coli wild type strain during fermentation in the presence of mixture of different carbon sources (glucose, formate, glycerol) in different assays at pH 7.5 was investigated. H2 was determined using redox potential measurements with a pair of platinum and titanium-silicate electrodes [2]. In glucose supplemented assays H2 producing activity was ~3 fold more than by the cells grown on glucose only as a sole carbon source. Interestingly, when glycerol was supplemented in the assays, H2 evolution was ~2 fold less than by the cells grown on glycerol only. Addition of formate in the assays resulted in increased H2 production: it was ~8 fold higher than by the cells grown on glucose only. Moreover, when the cells were grown in the presence of carbon mixture formate assays resulted in ~2 fold higher H2 production rate even when the cells were grown in the presence of glucose, glycerol and formate. When the cells were grown the presence of glycerol and formate in glycerol supplemented assays at pH 7.5 no difference was detected compared to the wild type cells grown on glycerol only. But in the formate supplemented assays H2 production rate was ~10 fold more compared to

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glycerol assays. Taken together it can be concluded that when the cells were grown in the mixture of glycerol and formate H2 production rate was similar or lower to the cells grown on glycerol or appropriate single carbon source. In addition, when the cells were grown in the presence of glucose, formate and glycerol H2 evolution was increased ~3 fold in glucose supplemented assays compared to the cells grown on glucose. The obtained results suggest using a mixture of carbon sources (glucose, formate and glycerol) or developing multi-stage technology to enhance H2 bio-production. 1. Trchounian K, Poladyan A, Vassilian A and Trchounian A (2012) Crit Rev Biochem Mol Biol 47, 236-249. 2. Trchounian K and Trchounian A (2014) Int J Hydrogen Energy, 39, 16914-16918.

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