Microbial community diversity during fermentative hydrogen production inoculating various pretreated cultures

This study adopted five pretreatment means (base, aeration, gamma-radiation, acid and heat-shock) for enriching hydrogen-producing bacteria from anaerobically digested sludge, aiming to investigate the microbial community diversity during fermentative hydrogen production using various pretreatments as inoculum. The experimental results indicated that all five pretreatments could effectively enrich hydrogen-producing bacteria from the seed sludge, while the microbial communities showed a great difference among various pretreated groups. The most three dominant genera were Paraclostridium (28.6%), Clostridium sensu stricto 1 (19.8%) and Terrisporobacter (19.4%) for base pretreated group, Enterococcus (67.2%), Clostridium sensu stricto 1 (10%) and Citrobacter (5.6%) for aeration pretreated group, Clostridium sensu stricto 1 (63.9%), Paeniclostridium (9.3%) and Romboutsia (7%) for gamma-radiation pretreated group, Clostridium sensu stricto 1 (51.9%), Romboutsia (22.4%) and Paeniclostridium (8.2%) for acid pretreated group, and Paraclostridium (61.2%), Exiguobacterium (23.1%) and Clostridium sensu stricto 1 (8.1%) for heat-shock pretreated group, respectively. Different microbial communities resulted in diverse process performance and metabolic pathway. Heat-shock pretreatment achieved the maximum hydrogen yield of 1.58 mol/mol-glucose and maximum hydrogen production rate of 37.65 mL/h. The dominance of genus Paraclostridium was supposed to be responsible for the highest hydrogen production. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.