Optimization of enzymatic hydrolysis for acid pretreated date seeds into fermentable sugars

Abstract One of the issues in the Middle East is that tons of date palm fruit waste are discarded by the date processing industries daily. Open burning to dispose agricultural residues can create environmental problems. To mitigate this issue, it is desirable to evaluate the potentials of the date palm wastes, such as date seeds, to be converted into value-added products. Date seeds were found to contain 27.34% lignin, 20.63% cellulose and 13.49% hemicellulose which can be hydrolysed into fermentable sugars. In this project, acid hydrolysis at 70 °C coupled with enzymatic hydrolysis proved to be able to deteriorate the lignin and cellulose in date seeds based on the physical changes observed with FESEM. Response surface methodology was used to determine the optimum condition; 120 FPU/g of cellulase for 6 h, at 45 °C. Under this condition, the maximum concentration of reducing sugars obtained from enzymatic hydrolysis is 31 g/L, making a total of 0.3 g/g of fermentable sugar obtained when combined with acid hydrolysis, equivalent to 81% from the theoretical value. Validation of the model indicated that there was no variance between the predicted (32.5 g/L) and observed values (31 g/L). This is the first work done on optimization of dates seeds into fermentable sugar under mild conditions.