Plant-associated microbial communities converge in fermentative hydrogen production and form a core microbiome

Abstract

This study presents the taxonomic characterization and fermentative activity of bacteria and fungi present in four plant-associated microbial communities: corn stover (CS), wheat straw (WS), sugarcane bagasse (SCB), and agave bagasse (AB). Fiber soaking, fermentation number, and organic loading rate (OLR) were studied in semicontinuous reactors fed with untreated substrates under a consolidated bioprocessing approach. WS, SCB, and AB communities converged to a core microbiome with the predominance of Lactobacillus, Clostridium, Enterobacter, and the fungus Pichia. After the fourth fermentation, hydrogen productivity became stable and similar among microbial communities (1.62 L-H2/kg-day), except for the CS community. The OLR increase promoted the hydrogen production from lactate and acetate. Lactobacillus positively correlated with H2 productivity and polysaccharide degradation, and Clostridium positively correlated only with polysaccharide degradation. Results demonstrated that Lactobacillus played a key role in producing high hydrogen productivities from lignocellulosic substrates. While the OLR increase promoted metabolic pathways that favored fermentative hydrogen production.