Effects of Enzyme Loading, Incubation Time and Incubation Temperature on Sawdust Hydrolysis by Locally Produced Bacterial Xylanase
The present study aims to investigate the enzymatic hydrolysis conditions of bacterial xylanase on alternative cheaper substrate which is hardwood sawdust (SD) in order to produce reducing sugars (xylose). The bacterial xylanase was produced and secreted from the Bacillus sp. The wood industry in Malaysia has become a major source of foreign exchange across the globe for developing the countries. Therefore, more wood residues (sawdust) are produced during the logging and processing of wood. Most of the sawdust will be disposed into the landfills. In actual, the sawdust can be utilised into more valuable products such as in producing reducing sugars. Thus, previous researches have studied on xylose production from wooden sawdust using commercial xylanases, but only few with the bacterial xylanase. Therefore, a study on the best conditions of enzymatic hydrolysis in producing xylose from sawdust using bacterial xylanase is essential. Prior to the enzymatic hydrolysis, the hardwood sawdust was pre-treated by autoclave at 121°C for 20 min in order to breakdown the lignin linkage and obtain the hemicellulosic xylan (delignification). The enzymatic hydrolysis conditions such as enzyme loading, incubation time and incubation temperature were experimented by One-Factor-At-Time (OFAT) method. Based on the experiment, the fifth cycle pre-treated autoclaved sawdust showed 5.5-fold higher than the untreated sawdust. The best enzymatic hydrolysis conditions for xylose production were enzyme loading of 1.4%, incubation time of 30 min, and incubation temperature of 56.9 °C. These conditions also succeeded in producing 2.5-fold higher xylose than the one without the enzymatic hydrolysis.