Optimization of microwave-assisted ultrasonication for improved saccharification in the production of bioethanol from ice apple shell (Borassus flabellifer)

Introduction The exploration of lignocellulosic wastes as potential feedstocks for biofuel has been propelled by the growing need for sustainable energy sources. The potential of ice apple shells as a substrate for the synthesis of bioethanol is assessed in this study. Methods The compositional, proximate and ultimate analysis were performed to assess the physicochemical compatibility of ice apple shells as a lignocellulosic feedstock. RSM-based CCD was used to optimize delignification in order to improve cellulose accessibility. The process performance was predicted using an ANN model with 5-fold cross-validation, and GA and PSO algorithms were used to determine the optimum delignification conditions. Structural and morphological analyses were performed to evaluate the changes in the lignocellulosic structure following optimized pretreatment. The acid hydrolysate and fermented broth were qualitatively characterized by UPLC-PDA and GC-MS respectively. Results The compositional analysis of the pretreated sample revealed 9.4% lignin, 53% cellulose, and 11.6% hemicellulose, indicating significant bioconversion capability. The resulting quadratic model demonstrated excellent predictive ability (R 2 = 0.998). A maximum delignification efficiency of 55.2% was attained at 90 °C, 30 min, and 1% NaOH concentration. Using the RSM regression equation together with GA and PSO, the optimum pretreatment conditions for the maximal delignification were found to be about 1% NaOH, 25 min, and 90 °C, with a predicted delignification efficiency of 64.91%. A maximum total sugar content of 52 mg/mL was obtained from subsequent acid hydrolysis, optimized at 1.5 M H 2 SO 4 , and this was effectively fermented into bioethanol with an ethanol concentration of 18 g/L. Discussion Thus, ice apple shells used as a lignocellulosic feedstock show how statistical analysis and machine learning can be combined to improve biofuel production methods.