Alkaline hydrolysis for yield of glucose and kraft lignin from de-oiled Jatropha curcas waste: multiresponse optimization using response surface methodology

In this study, an attempt has been made to recover the lignin and enhance the sugar yield from the de-oiled Jatropha curcas waste (DJW) through alkaline hydrolysis and saccharification. The alkaline hydrolysis process was performed using sodium hydroxide (NaOH) for a solid loading rate of 10% w/v. The process parameters considered for the optimization study using RSM were — time (6.36–73.63 min), NaOH concentration (0.6137–12.38%), and temperature (85.68–156.3°C). The maximum kraft lignin (KL) recovered at the optimum conditions for the response was found to be 93.4%. The functional groups in the treated and untreated Jatropha curcas seed cake and the recovered lignin were studied using FTIR. The recovered kraft lignin has been characterized using 1H-NMR and FTIR. The enzymatic saccharification efficiency was estimated based on the release of glucose. Maximum glucose yield (%) was found to be 92.45% for NaOH pretreated DJW compared to the untreated biomass, for which the glucose yield was only 46.64%.