Isolation of hydrogen-producing bacteria from granular sludge of an upflow anaerobic sludge blanket reactor

Abstract

H2-producing bacteria were isolated from anaerobic granular sludge. Out of 72 colonies (36 grown under aerobic conditions and 36 under anaerobic conditions) arbitrarily chosen from the agar plate cultures of a suspended sludge, 34 colonies (15 under aerobic conditions and 19 under anaerobic conditions) produced H2 under anaerobic conditions. Based on various biochemical tests and microscopic observations, they were classified into 13 groups and tentatively identified as follows: From aerobic isolates,Aeromonas spp. (7 strains),Pseudomonas spp. (3 strains), andVibrio spp. (5 strains); from anaerobic isolates,Actinomyces spp. (11 strains),Clostridium spp. (7 strains), andPorphyromonas sp. When glucose was used as the carbon substrate, all isolates showed a similar cell density and a H2 production yield in the batch cultivations after 12h (2.24–2.74 OD at 600 nm and 1.02–1.22 mol H2/mol glucose, respectively). The major fermentation by-products were ethanol and acetate for the aerobic isolates, and ethanol, acetate and propionate for the anaerobic isolates. This study demonstrated that several H2 producers in an anaerobic granular sludge exist in large proportions and their performance in terms of H2 production is quite similar.