Alkali delignification and Bacillus sp. BMP01 hydrolysis of rice straw for enhancing biofuel yields

Abstract

Lignocellulose biomass such as agricultural residues is increasingly important for biofuel production. Using agricultural residues like rice straw for biofuel production has dual purposes of utilizing the huge waste generated. The abundant availability and high polysaccharide contents are the main reason for biofuel production. However, the use is limited due to the reluctant nature of lignin in the biomass. Therefore, sodium hydroxide was used for solubilizing lignin and preserving the polysaccharides. About 71.29% of lignin (maximum amount of lignin) was removed after 7% sodium hydroxide (NaOH) pretreatment followed by 3% pretreatment (about 67.13%). Also, maximum cellulose (about 71.33%) was preserved after 7% NaOH pretreatment. Results of reducing sugars obtained by spectrophotometric analysis (3,5-dinitrosalycilic acid method) of pretreated rice straw show about 88.27% conversion (753 mg/g) after the 13th day of hydrolysis by bacteria isolated from a termite. FE-SEM, XRD, FTIR, and TGA analyses show a significant amount of lignin was removed which helps in releasing cellulose tangled in lignin. Rice straw pretreatment at 7% NaOH and hydrolysis by Bacillus sp. BMP01 achieved the release of a high yield of fermentable sugars that increased the yield of bioethanol. This study demonstrates the potential of alkali pretreatment coupled with microbial hydrolysis for efficient bioethanol production from agricultural residues like rice straw.