Two stage pretreatment of dates seeds for fermentable sugar production

Currently, date seeds are considered as waste and contribute to the waste disposal problem. To mitigate this issue, it is desirable to impart an economic value on date seeds so that they can be utilized instead of going to waste. The lignocellulosic part of date seeds are composed mainly of hemicellulose, cellulose and lignin. Hemicellulose and cellulose can be hydrolyzed into sugars which can then be fermented into ethanol. Thus, the objective of this research is to evaluate the effect of temperature, reaction time and agitation speed on the acid hydrolysis using the one factor at a time (OF AT) method. For the enzymatic hydrolysis using cellulase, the optimization was done using OFAT and CCRD. In the OFAT method, three factors were applied, cellulase concentration, temperature and time of reaction. A two variable Central Composite Rotatable Design (CCRD) for response surface methodology (RSM) was employed to evaluate the simultaneous effect of enzyme concentration and reaction time on the obtained total reducing sugar concentration after hydrolysis. It was found that the date seeds contain 27.34% lignin, 20.63% cellulose and 13.49% hemicellulose. The optimal condition for acid hydrolysis using OF AT was found to be at 1% sulphuric acid concentration, 70°C for 2 hours, and agitation speed of 200 rpm. Under these conditions, the maximum concentration of reducing sugars obtained was 29.81 giL. The second stage uses cellulase enzyme to hydrolyse the cellulose content in powdered date seeds into fermentable sugars. A validated quadratic statistical model was developed to relate the hydrolysis variables to the total sugar concentration. The optimal conditions of enzymatic hydrolysis as obtained from OF AT was when the activity of cellulose enzyme was at 90 FPU/g for 10 hours at 40°C. While for CCRD, the optimum condition was obtained by 120 FPU/g for 6 hours at 45°C. Under the optimum condition, the maximum concentration of reducing sugars obtained was 31 g/L. Validation of the model indicated that there was no variance between the observed and predicted values. The total sugar content obtained from the two stage process altogether was 60.8 g/L, 80% from the theoretical value.