Synthesis of Hydroxycinnamic Acid Esters Integrated with Aqueous Two-Phase System and Production of Fermentable Sugars from Corncobs

The fractionation of lignocellulosic biomasses has been widely reported as a way to establish biorefineries. However, more efforts are needed to valorize lignin and its phenolic derivatives in the production chain. Thus, the present study investigated the production of hydroxycinnamic acid esters and monosaccharides from an integrated scheme using corncob as raw material. After alkaline pretreatment, p-coumaric acid and ferulic acid were released in the liquid fraction (1.91 and 0.81 mg/mL), and they were isolated/concentrated in an aqueous two-phase system (ATPS) ethanol/ammonium sulfate. The best ATPS led to a high recovery in the top phase, corresponding to 89.7% for p-coumaric acid and 90.5% for ferulic acid. Direct esterification of the ATPS top phase with 20% (v/v) sulfuric acid guaranteed 1.60 mg/mL ethyl p-coumarate and 0.67 mg/mL ethyl ferulate, both products with potential application in cosmetics. Xylan was recovered in the ATPS and was successfully converted into xylose via acid hydrolysis (yield of 69% under 10% solids). The pretreated corncob was digested to obtain 99.6 g/L glucose under 30% solids in fed-batch mode using cellulase loading of 5 FPU/g and 2% (w/w) Tween 80. These results are in line with the idea of ​​comprehensive use of lignocellulosic biomass, especially in the development of lignin-derived products with high added value.