Influence of lignin level of raw material on anaerobic digestion process in reorganization and performance of microbial community

Abstract

Huge quantum of agricultural crop residue from agrarian economies like India is disposed of improperly by open land burning contributing to particulate and gaseous pollutants thereby severely impacting the environment and human health. There is an overwhelming need for sustainable utilization of this misplaced resource as feedstock in biofuel production through anaerobic digestion. Substrate composition influences the digestibility of the substrate and underlying microbial plasticity involved in anaerobic digestion. In this study, anaerobic inoculum was subjected to enrichment in the presence of agricultural residues with different lignin content whose influence on biogas production, and differential modulation/ reorganization of microbial communities was explored. BMP assay emphasized the inverse proportionality between lignin content and biogas yield, with highest biogas yield of 622 mL/g VS added in case of rice straw (lowest lignin, 16.9%), followed by wheat straw-556 mL/g VS (18.12% lignin), sugar cane leaves-451 mL/g VS (21.87% lignin), and lowest biogas yield of 411 mL/g VS added in case of cotton crop waste (highest lignin, 23.97%). Biogas production efficiency was correlated with the selection and shift of microbial communities to key hemicellulolytic (Bacteroides, Clostridium, Prevotella, Thermotoga, Cytophaga) and lignocellulolytic (Bacillus, Geobacter, Flavobacterium, Spirochaeta, Klebsiella, Escherichia, Pseudomonas, Burkholderia) genotypes in comparison to initial anaerobic inoculum. Study highlighted that the variable lignin content resulted in genomic reorganization and created a scenario for high biogas production by selectively enriching different methanogenic pathways such as hydrogenotrophic pathways in rice straw metagenome (lowest lignin) and acetoclastic pathways in cotton crop waste metagenome (highest lignin).

Uncovering Microbiome Adaptations in a Full-Scale Biogas Plant: Insights from MAG-Centric Metagenomics and Metaproteomics

“…Interestingly, the high expression of a gentisate 1,2dioxygenase by MAG 267 might be related to the degradation of aromatic compounds (e.g., lignin components and aromatic amino acids). This enzyme was also shown for anaerobic organisms, such as Syntrophus gentianae [120], and as a functional gene of microbial communities involved in the anaerobic digestion of cotton waste and rice straw [121]. MAG 267 also harbors the complete aromatic degradation KEGG Module (M00569, Catechol metacleavage) and several enzymes involved in the degradation of aromatic compounds.…”

New trends in microbial lipid-based biorefinery for fermentative bioenergy production from lignocellulosic biomass

“…Often, selective enzymes are preferred over whole microbial cells to ensure rapid catalysis, swift conversion, and reduced contamination during LCB pretreatment. The systematic application of enzyme cocktails has been proven to catalyze more efficiently than using them individually (Nakhate et al, 2021). Pretreating solid digestate, primarily composed of organic waste like fruit and vegetable residues, with P. sajor-caju has been reported to increase VFA yield by 1.24 and 1.17 folds compared to untreated substrate and substrate treated withautoclaving, respectively (Fang et al, 2018).…”