Ethanol Production from Corncob Assisted by Polyethylene Glycol and Conversion of Lignin-Rich Residue into Lignosulfonate and Phenolic Acids

The economic competitiveness of 2G-bioethanol technology should improve through the improvement of the sugar release and the valorization of by-products, especially lignin. Thus, an integrated scheme with corncob was developed to produce ethanol using low dosages of cellulases and value-added products from the semi-simultaneous saccharification and fermentation (SSSF) residue. Enzymatic hydrolysis and SSSF of acid pretreated corncob (< 20 mesh and > 20 mesh) were carried out under cellulase dosages of 5, 10, and 15 FPU/g in the absence and presence of polyethylene glycol 1500 (PEG 1500). The SSSF residue was used to obtain lignosulfonate via sulfomethylation reaction and phenolic acids via alkaline hydrolysis using 4% (w/v) sodium hydroxide and 0–5% (v/v) hydrogen peroxide. Pretreated corncob < 20 mesh allowed the reduction of cellulase dosage to 5 FPU/g without compromising sugar release. The addition of PEG 1500 boosted sugar release, reaching 56.73 g/L glucose under 20% (w/v) solids. The maximum ethanol production of 31.64 g/L was obtained using 5 FPU/g cellulases, 2% (w/w) PEG 1500, and 20% (w/v) solids (gradual addition). FTIR confirmed the preparation of lignosulfonate from SSSF residue, and the surfactant showed good stabilization performance in oil/water systems (emulsification index≈30%). High yields of p-coumaric acid (8045.3 mg/100 g) and ferulic acid (1429.4 mg/100 g) were obtained in alkaline hydrolysis with 5% (v/v) hydrogen peroxide. Based on these findings, corncob is versatile and can create a biorefinery with high economic potential.