The effect of the surface charge of different immobilizing hydrogels on biohydrogen production in batch cultures was investigated using a novel isolate associated to the genus Thermoanaerobacterium. Two crosslinked polysaccharide-based hydrogels and two acrylic hydrogels were tested as polymeric carriers for cell adsorption. Immobilization improved both substrate conversion and hydrogen cumulative production compared to the suspended culture, and a yield of 1.9 mol H(2)/mol glucose was observed after 24h for alginate-supported cultures. Cationic carriers dramatically increased cell immobilization, leading to markedly faster kinetics of substrate degradation and hydrogen production in batch operation, with a peak of 3.6 mol H(2)/mol glucose for the acrylic hydrogel HM92. Accumulation of gaseous and acidic metabolites inhibited further H(2) production, shifting the carbon flow to reduced end-products and biomass synthesis. Preliminary tests showed that all the tested hydrogels had good durability and allowed hydrogen production on repeated batch runs.
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