Bioconversion of lignin and methane production from Corn cobs (Zea mays) treated by lignin-degrading bacteria

Corn cobs are one of the potential feedstocks consisting of cellulose, hemicellulose and lignin, which provide potential lignocellulose biomass to be converted into renewable energy such as biogas through anaerobic digestion (AD). However, the recalcitrant structure of corn cobs lignocellulose makes it resistant to microbial access to the cell wall, and therefore the effective pre-treatment needs to be conducted. The biological pre-treatment using lignin-degrading bacteria is one of the promising bioconversion processes which will help to break down the lignocellulose structure. This study aims to analyse the ability of bacteria, Agrobacterium sp., Lysinibacillus sphaericus and Paenibacillus sp. in degrading lignin of corn cobs and therefore will enhance the methane released from AD. The ability of bacteria to degrade lignin was observed by analysis of total reducing sugar, total soluble phenols, lignin content, and weight loss, while the methane production was determined by the biochemical methane potential (BMP). The percentage of lignin content of untreated and pre-treated corn cobs with bacteria Agrobacterium sp., L. sphaericus and Paenibacillus sp. is 18.34%; 9.66%; 11.48% and 9.06%, respectively. The methane concentration (specific methane production) produced by using inoculum of Agrobacterium sp., L. sphaericus and Paenibacillus sp. with the addition of pre-treated corn cobs are 1.79%; 1.16% and 2.51%, respectively. These results were higher than the inoculum with the addition of untreated corn cobs.