Optimisation of SSF Parameters for Cellulase Production by Aspergillus niger via Solid-state Fermentation using Rice Husk as Substrate

Cellulase enzyme comprises of endoglucanase or carboxymethyl cellulase (CMCase), exoglucanases or cellobiohydrolase and cellobiases or β-D-glucoside glucohydrolase (β-glucosidase). For economical bioconversion of rice husk into cellulase production, it requires high efficient hydrolysis of cellulose to glucose and cellulase via optimisation of solid-state fermentation parameters. This study looks at the optimal initial moisture content, incubation temperature and period for cellulase production by Aspergillus niger via SSF using rice husk as substrate. Ground rice husks were pretreated with 2.5 % (w/v) sodium hydroxide solution. A. niger was sub-cultured on potato dextrose agar and then incubated at room temperature until fully grown. Solid-state fermentation was carried out with incubation of 5 g of substrate with three plugs of A. niger at 25 °C – 40 °C for two to eight days at 60 % (v/w) to 75 % (v/w) initial moisture content under static condition. Supernatant or crude enzyme extract was successfully obtained and then, the cellulase activity of the crude enzyme was determined using filter paper assay and dinitrosalicylic acid method. Fermented rice husk with A. niger recorded the highest cellulase activity at 0.3202 ± 0.0179 U/ml with the optimal condition at 25 °C, 2 days and 65 % (v/w). These results indicate that rice husk can serve as a cheap and environmentally friendly cellulose source in solving economic issues and enhancing the industrial potential of cellulase production by A. niger under solid-state fermentation