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Combined heterogeneous catalysis and dark fermentation systems for the conversion of cellulose into biohydrogen

Abstract:

A two-step combined system consisting of heterogeneous catalysis followed by dark fermentation was investigated for the production of biohydrogen. Cellulose in the aqueous phase was hydrolysed in an autoclave reactor with ZrO<inf>2</inf> catalysts modulated by three different promoters: sulfate, fluoride, and phosphate. The water-soluble fractions (WSFs) resulting from the catalytic cellulose hydrolysis were then submitted to dark fermentation without any additional treatment. The dark fermentation step tested three different microorganisms - Enterobacter spH1, Citrobacter freundii H3 and Ruminococcus albus DMS20455 - for their ability to produce H<inf>2</inf> from cellulose, glucose and the liquid product derived from cellulose hydrolysis. The two enteric bacteria (C. freundii H3 and Enterobacter spH1) effectively fermented the WSFs to produce H<inf>2</inf> and other organic compounds as metabolites. For the WSFs derived from cellulose hydrolysis with ZrO<inf>2</inf>-P and ZrO<inf>2</inf>-S catalysts, the values for Enterobacter spH1 were 1.40 and 1.09molH<inf>2</inf>/molhexose, respectively.