Valorization of Bombax ceiba Waste into Bioethanol Production through Separate Hydrolysis and Fermentation and Simultaneous Saccharification and Fermentation

Abstract

In this study, Seed pods of B. ceiba were used as a novel, cheap, and sustainable feedstock for second-generation bioethanol production. B. ceiba waste was pretreated with NaOH under different conditions using a Box–Behnken design (BBD) with three factors and three levels. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to investigate the chemical, structural, and morphological modifications made by pretreatment. NaOH pretreatment followed by steam was more effective as it offered 60% cellulose and 9% lignin at 10% substrate loading, 5% NaOH conc., and 4 h residence time. Samples with maximum cellulose were employed for ethanol production by separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) using indigenously produced cellulase as well as commercial cellulase. HPLC analysis revealed the best saccharification (50.9%) at 24 h and the best ethanol yield (54.51 g/L) at 96 h of fermentation in SSF using commercial cellulose by Saccharomyces cerevisiae. SSF offered a better production of bioethanol from seed pods than SHF. The implications of the work support the notion that B. ceiba waste could be utilized for large-scale bioethanol production.