Effect of Microwave Treatment on Acid and Enzymes Susceptibilities of Sago Pith

Sago palm is considered to be an ideal crop for starch-based sweetener and alcohol fuel feedstock since there is negligible competition between food and fuel in Indonesia and land resources were under-utilized. Starch accumulates in the pith of the sago trunk. Composition of dried sago pith is mainly starch and fiber components. Direct conversion of sago pith into fermentable sugar will reserve the water and save the energy for starch extraction and drying. This research investigated the effects of sago pith pretreatment as heating in water and in dilute sulfuric acid using microwave heating and autoclaving. Liquefaction of starch was conducted using alpha-amylase on 95 degrees C, and enzyme consortium between dextrozyme (amyloglucosidase and pullunase), cellulase dan xylanase on 50 degrees C for saccharification process. Changes on structures were monitored by microscopy examination, and filtrate characteristics. Conversion process which included the pretreatment was carried out by microwave heating in water or in dilute acid, starch, and fiber hydrolysis into fermentable sugar. The results shows that direct heating of sago pith in water by microwave treatment can swell and gelatinize the starch, make the fiber more amorphous and more susceptible for enzyme reaction. Heating in dilute acid directly converted the starch and fiber into depolymerized products and gave more simple sugars (DP of 1.11-2.56) compared to autoclaved heating of sago pith (DP of 2.00-2.11). Microwaved-treatment produced lower DP of sugars during liquefaction (DP of 3.8-13.3) compared to autoclaved heating (DP of 7.3), but expressed some higher DP of sugar during saccharification (DP 3.1-3.8) compared to autoclaved heating (DP of 3.0). (C) 2012 Published by Elsevier Ltd.