STUDY OF MULTISTAGE CHEMICAL HYDROLYSIS OF WHEAT STRAW AND UTILISATION OF HYDROLYSATES BY Lentibacillus salarius BPIITR

Abstract

Current study investigates the potential of wheat straw (ws) fractionation coupled with valorization through fermentation by the halophilic bacterium Lentibacillus salarius BPIITR. Initially, the chemical composition of untreated wheat straw was analyzed, the total solid content was 92.9 ± 0.07 % comprising 33.01 ± 0.16% cellulose, 23.88 ± 0.13% hemicellulose, 23.47 ± 0.60% acid-insoluble lignin, 1.82 ± 0.04% acid-soluble lignin, 8.40 ± 0.5 % ash, and remaining are extractives. A fractional factorial design followed by a Box-Behnken design was employed to optimize the alkaline wet oxidative pretreatment (AWOP) and acid hydrolysis conditions for maximum sugar release. The optimal conditions were determined to be 0.048 g/g sodium hydroxide, 127 °C acid hydrolysis temperature, 150 min acid hydrolysis time, and 0.1 g/g sulfuric acid. Under these conditions, a total sugar yield of 251.5 ± 6.91 mg/g ws was achieved, comprising 22.93 ± 1.10 mg/g ws hexose sugars and 228.57 ± 7.74 mg/g ws pentose sugars. This resulted in an 84.23% recovery of hemicellulose, significantly higher than previous studies reporting 43.1-57.12% recovery. The study then investigated the potential of artificial seawater for cellulose hydrolysis using a central composite design. Optimal conditions for artificial seawater-based hydrolysis were identified as 169 °C, 61 min reaction time, and 0.131 g/g acid concentration, yielding total sugar of 310.68 ± 1.88 mg/g of cellulose-rich residual ws. This represented a substantial improvement over the distilled water method, which produced total sugar, 139.36 ± 2.58 mg/g of cellulose-rich residual ws under its optimal conditions (148 °C, 126 min, 0.461 g/g acid concentration).