Advances Towards the Understanding of Microbial Communities in Dark Fermentation of Enzymatic Hydrolysates: Diversity, Structure and Hydrogen Production Performance

Microbial communities involved in hydrogen (H-2') production from enzymatic hydrolysates of agave bagasse were analyzed through 16S rRNA sequencing. Two types of reactor configurations and four different enzymatic hydrolysates were evaluated. Trickling bed reactors led to highly-diverse microbial communities, but low volumetric H-2 production rates (VHPR, maximum: 5.8 L H-2/L-d). On the contrary, well-controlled environments of continuous stirred-tank reactors favored the establishment of low diverse microbial communities composed by Clostridium-Sporolactobacillus leading to high-performance H-2-production (VHPR maximum: 13 L H-2/L-d). Cellulase-Viscozyme and Celluclast-Viscozyme hydrolysates led to the co-dominance of Clostridium and Sporolactobacillus, possibly due to the presence of xylose and hemicellulose-derived carbohydrates. Cellulase hydrolysates were linked to communities dominated by Clostridium, while maintaining low abundance of Sporolactobacillus. Stonezyme hydrolysates favored microbial communities codominated by Clostridium-Lachnoclostridium-Leuconostoc. Moreover, contrary to the prevailing theory, it was demonstrated that H2C production performance was inversely related to microbial diversity. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.