Lignocellulosic materials are becoming a sustainable feedstock to produce biofuels and to alleviate a series of environmental pollutions. In order to break down the irregular noncrystalline structure of lignin so as to make the (hemi)cellulosics bioavailable, establishing unique microbial consortia that utilize raw lignocellulosic biomass (especially lignin, synergistically as in nature) is a priority for sustainable and economical biofuel generation. In this study, a microbial consortium (LI3) was obtained from a paddy field sediment with lignin as the sole carbon source under anaerobic conditions. Consortium LI3 produced high amount of methane (up to 3.61 ppm mg-1 lignin) while depolymering lignin structure from high molecular weight to low molecular weight. The combination of lignin depolymerization and methanogenesis can facilitate to convert the greenhouse gas (CO2) to biofuels (CH4) and in the meanwhile to improve the bioavailability of lignocellulosic materials for following hydrolysis. Moreover, results from application on the oil palm empty fruit bunch fiber (OPEFB) model feedstock showed that LI3 can also utilize the OPEFB to produce the methane (up to 4.54 ppm per mg-1 OPEFB), and reducing sugars (24% more) were generated by cellulase hydrolysis from OPEFB with LI3 than that from the autoclaved controls, suggesting that culture LI3 plays a positive role in the lignin destruction to improve the bioavailability of lignocellulosic matters for further application. The analysis of microbial community by denature gradient gel electrophoresis (DGGE) indicates that the dominant methanogens species in culture LI3 is usually uncultivable, which belong to Methanosarcinaceae family, and one of them was identified as Methanomethylovorans species. Further survey with high-density 16S rDNA gene microarray (PhyloChip) exhibited 33 phylotypes from total 2685 operational taxonomic units (OTUs). In all, a microbial consortium with novel microbes demonstrates effective depolymerization of lignin and methane production simultaneously, which has profound application in pretreatment of lignocellulosic materials.

Depolymerization of lignin by anaerobic microbial consortia

243rd National Meeting (2012)

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