Microbial lignin degradation in an industrial composting environment
Katharina Duran, Marijn van den Dikkenberg, Gijs van Erven, J.J.P. Baars, Rob N.J. Comans, Thomas W. Kuyper, Mirjam A. Kabel
Abstract
Composting is an essential biochemical process to pre-treat lignocellulosic biomass (e.g., wheat straw) to generate nutritious substrate for industrial Agaricus bisporus production. During composting numerous microbes target (hemi-)cellulose using their enzymatic machinery, while lignin has been assumed to remain unaffected. This research aimed to unravel the chemical and microbial changes during a 4-day industrial composting process with special emphasis on the fate of lignin. A recently developed pyrolysis-GC–MS method using a 13C-lignin isolate as internal standard enabled targeted quantitative lignin analysis. As previously demonstrated, a 40% w/w decrease in (hemi-)cellulose was observed, while unexpectedly lignin decreased by 30% w/w. Increased Cα-oxidized moieties and cleaved interunit linkages substantiated this lignin removal. Simultaneously, a microbial community shift towards Alphaproteobacteria, Gammaproteobacteria, Actinobacteria and Sordariomycetes occurred. Hence, the compost environment provided appropriate conditions to harbor a microbial community to alter and degrade lignin, and this research provides new insights into underlying lignin degradation mechanisms.