Highly crystalline cotton spinning wastes utilization: Pretreatment, optimized hydrolysis and fermentation using Pleurotus florida for bioethanol production

Due to highly deleterious effects of physico-chemical pretreatment of lignocellulosic biomass to environment, the 2G biofuel production requires more sustainable and eco-friendly approach. During this study, the effect of biological pretreatment on fibrous cotton spinning waste mixture (CSWM) was investigated using solid-state cultivation of white-rot fungi, Pleurotus florida. The pretreatment with P. florida showed significant amount of lignin degradation (similar to 60 %w/w) and similar to 80-85% of cellulose crystallinity reduction with the cellulose content of 80.7%w/w, after 14 days of pretreatment. This was also evidenced by Attenuated Total Resonance - Fourier Transform Infrared (ATR-FTIR) spectroscopy and Scanning Electron Microscopy (SEM). Optimization of hydrolysis conditions using Central Composite Design (CCD) resulted in the R-squared (R-2) value and desirability of 0.97 and 0.95, respectively. The optimized conditions were biomass loading of 0.67%w/v and enzyme loading of 60 FPU/g of cellulose results in hydrolysis efficiency of similar to 70% after 96 h. The hydrolysate, supplemented with mineral salts and 3 %v/v of inoculum, were maintained at anaerobic conditions with 32 +/- 2 degrees C for 72 h. Optimum ethanol yield of 64 % (1.18 g/L) was obtained after 60 h of fermentation. This finding suggests that microbial pretreatment can effectively be employed for the sustainable and green production of bioethanol with more economical value.