Enhanced biogas production from rice straw through pretreatment with cellulase producing microbial consortium

Rice straw (RS) is a rich lignocellulosic biomass that can be employed for biogas generation through anaerobic digestion. However, lignin-silica encrustation around the holocellulose complex hinders its digestibility. Therefore, in this present study, RS was biologically pretreated with microbial consortium of Punjab Agricultural University (PAU decomposer), which is composed of Bacillus sp., Delftia sp., Pseudomonas sp., Lysinibacillus fusiform, Arthrobacter nicotianae, Paenibaccilus ehimensis, Aspergillus sp. and Trichoderma sp. Bio-digested slurry, the underutilized spent waste from cattle dung-based biogas plants was used as a growth medium for the mass multiplication of consortium. Soaked and chopped RS was pretreated with consortium and individual cultures in triplicate sets for 5 and 10 d and were analyzed for biochemical parameters along with cellulolytic activity. The pretreated straw was used for biogas production in 2 L capacity anaerobic digesters. Cellulolytic activities i.e., endoglucanase (0.071 IU/mL), exoglucanase (0.027 IU/mL) and β-glucosidase (3.734 IU/mL) of consortium treated RS were higher as compared to untreated RS. Biogas production from consortium pretreated RS was 187.45 L/kg RS which is 45.93% more as compared to untreated RS with 128.45 L/kg RS of biogas. This could be attributed to the synergistic cellulolytic activities of PAU decomposer leading to enhanced biogas production from RS.