Lipopeptide Biosurfactants Enhanced Biohydrogen Evolution from Lignocellulose Biomass and Shaped the Microbial Community and Diversity

Abstract

Biohydrogen is a renewable and clean energy source that can be produced from cheap and abundantly available lignocellulose biomass. However, the complex structure of lignocellulose requires various physicochemical and biological pretreatments, as it exhibits significant resistance to microbial degradation. Biosurfactants can play a vital role in facilitating the microbial degradation of lignocellulose and inducing enzymatic hydrolysis. In addition, they can lower the surface tension to impede lignin-cellulase interactions and alter the lignin characteristics. Indeed, the application of lipopeptide biosurfactants to enhance hydrogen production from lignocellulose biomass is poorly studied. Thus, this study investigates the influence of lipopeptide biosurfactants on biohydrogen enhancement from lignocellulose biomass and their impact on short-chain fatty acid generation during anaerobic dark fermentation. Subsequently, Illumina HiSeq 2500 sequencing was employed to analyze the structure of microbial community and diversity significantly affected by the presence or absence of aided biosurfactants. Results revealed that the lipopeptide biosurfactant significantly improved the cumulative biogas and hydrogen production. The maximum cumulative hydrogen yield was achieved in lipopeptide-assisted bioreactors including BioR_3, BioR_2, and BioR_4 (i.e., 4.68, 4.56, and 4.50 mmol/2 g of substrate, respectively), showing an increase of 30.79% to 36.03% higher than BioR_1 (3.44 mmol). In addition, lipopeptide biosurfactants also impacted the short-chain fatty acid generation, where acetic acid, propionic acid, and isobutyric acid were found as major acids. On the other hand, various bacterial phyla, including Firmicutes, Proteobacteria, Actinobacteria, Chloroflexi, Planctomycetota, and Acidobacteriota, were detected in all bioreactors. Among the phyla, Firmicutes were predominated (54.74% to 86.38%) in lipopeptide-assisted bioreactors, indicating that biosurfactants substantially influenced the microbial community structure during hydrogen production. Besides, Ruminiclostridium and Bacillus were significantly promoted in lipopeptide-assisted bioreactors, representing efficient lignocellulose-degrading and hydrogen-producing genera. Conclusively, this study offers valuable insights into the underlying mechanism through which lipopeptide biosurfactants actively participate in biohydrogen production and illuminates the variations occurring within microbial communities.