Rice straw is one of the most abundant agricultural by-products in Thailand. It generally contains
approximately 39% cellulose, 27% hemicellulose and 12% lignin. Cellulose and hemicellulose, when hydrolyzed
by chemical or enzymatic hydrolysis, are converted into glucose and other fermentable sugars for ethanol
production. In this study, screening of cellulolytic microorganisms for degrading rice straw has been investigated.
Twenty nine bacterial isolates and the 30 fungal isolates were selected for further study on their cellulolytic activity.
All isolates were assayed for exoglucanase, endoglucanase and β-glucosidase specific activities, by which
following substrates were used: filter paper (Whatman No.1), carboxymethyl cellulose and cellobiose, respectively.
Specific activities of those enzymes were determined by measuring reducing sugar released from substrates.
From the results, the following isolates showed the highest specific activity of each catagory of cellulases; FR14
for Filter paper cellulase (FPase) (0.032 unit/ mg protein), FR4 for CMCase (0.5 unit/ mg protein) and FC1 for
cellobiase (0.6 unit/ mg protein). Two isolates showed nearly equal activitiy of CMCase and cellobiase. The
isolate FR3 had 0.22 unit/ mg protein CMCase specific activity and 0.23 unit/ mg protein cellobiase specific
activity, while the isolate FR18 showed CMCase specific activity with 0.25 unit/ mg protein and cellobiase specific
activity with 0.30 unit/ mg protein.