Bacterial endophytes-mediated lignin degradation and co-culture fermentation of ryegrass for bioethanol production

Abstract

The recalcitrant nature of lignin hinders the lignocellulosic biomass conversion by inhibiting enzymes access to hemicellulose and cellulose. In the present study, the lignin degradation of ryegrass biomass was enhanced via pretreatment by three selected ligninolytic enzyme producing endophyte bacteria. Spectroscopic analyses clearly displayed disruption and decomposition of the biomass structure after the pretreatments. The optimum sugar utilization efficiency was reached at 93.46 % in Bacillus cereus pretreatment, with the highest bioethanol production of 0.51 g/g and 85.78 % bioethanol yield (P ≤ 0.05) after the co-culture anaerobic fermentation. The initial yeast population of 1.65 × 10⁷ cells mL⁻¹ was decreased to 1.56 × 10⁷ cells mL⁻¹ in co-culture of Saccharomyces cerevisiae YPH499 and Pachysolen tannophilus 32691, presenting the significant consumption of yeast cells. The study revealed that bacterial pretreatment could be a viable strategy for delignification of biomass and co-culture fermentation might enhance bioethanol yield from pretreated ryegrass.