Cotton stalks (CS) are considered a good candidate for fuel-ethanol production due to its abundance and high carbohydrate content, but the direct conversion without pretreatment always results in extremely low yields due to the recalcitrant nature of lignocelluloses. The present study was undertaken to investigate the effect of various chemical and physicochemical pretreatment methods, i.e., alkali, microwave-assisted acid, organosolv, hydrothermal treatment, and sequentially organosolv and hydrothermal pretreatment, on chemical composition of CS and subsequent ethanol production applying pre-hydrolysis and simultaneous saccharification and fermentation (PSSF) at high solid loading. The best results in terms of ethanol production were achieved by the sequential combination of organosolv and hydrothermal pretreatment (32.3 g/L, using 15% w/v substrate concentration and 6 h pre-hydrolysis) with an improvement of 32% to 50% in ethanol production compared to the other pretreatments. Extending pre-hydrolysis time to 14 h and increasing substrate concentration to 20% w/v, ethanol production reached 47.0 g/L (corresponding to an ethanol yield of 52%) after 30 h of fermentation.

Waste management and production of clean and affordable energy are two main challenges that our societies face. Food waste (FW), in particular, can be used as a feedstock for the production of ethanol because of its composition which is rich in cellulose, hemicellulose and starch. However, the cost of the necessary enzymes used to convert FW to ethanol remains an obstacle. The on-site production of the necessary enzymes could be a possible solution. In the present study, the multienzyme production by the fungus Fusarium oxysporum F3 under solid state cultivation using different agroindustrial residues was explored. Maximum amylase, glucoamylase, endoglucanase, b-glucosidase, cellobiohydrolase, xylanase, b-xylosidase and total cellulase titers on wheat bran (WB) were 17.8, 0.1, 65.2, 27.4, 3.5, 221.5, 0.7, 0.052 and 1.5 U/g WB respectively. F. oxysporum was used for the hydrolysis of FW and the subsequent ethanol production. To boost ethanol production, mixed F. oxysporum and S. cerevisiae cultures were also used. Bioethanol production by F. oxysporum monoculture reached 16.3 g/L (productivity 0.17 g/L/h), while that of the mixed culture was 20.6 g/L (productivity 1.0 g/L/h). Supplementation of the mixed culture with glucoamylase resulted in 30.3 g/L ethanol with a volumetric productivity of 1.4 g/L/h.