ศักยภาพของวัสดุเหลือทิ้งทางอุตสาหกรรมเกษตรในการเป็นสับสเตรตสำหรับผลิตเซลลูเลสจากเชื้อราภายใต้การหมักสภาพอาหารแข็ง

Abstract

Four agro-industrial by-products, including corn-cobs, coconut hulls, corn-husks and peanut hulls, were selected as substrates in the production of cellulase enzymes. These biomass substances were ground and pretreated with diluted acid and alkali. The cellulose content was found to be the highest in the peanut hulls (33.82 percent), followed by corn husks, coconut hulls and corn-cobs which were 22.94, 26.29 and 13.87 percent, respectively. In this study, 5 white-rot fungi, Pycnoporus coccineus, Pycnoporus sanguineus, Trametes pavonia, Ganoderma australe and Ganoderma mastoporum, which exhibited potential for carboxymethyl cellulose degradation on CMC agar were cultured by solid state fermentation using corn-cobs, coconut hulls, corn husks and peanut hulls as substrates for cellulase production. The cellulase activity, filter paper activity (FPase), carboxymethyl cellulase (CMCase) and cellobiase activities were analyzed after solid state fermentation (SSF) under static conditions at 25°C for 12 days with an initial moisture content of 60-90% and an initial pH value of 5.5. The results showed that P. coccineus and P.sanguineus provided the highest enzyme activity over 9 days of fermentation when using corn-cobs and peanut hulls as substrates at 70 percent initial moisture content. Therefore, the optimal conditions (initial pH value, incubation temperature, nitrogen sources and inducer) for cellulase production from P. coccineus and P. sanguineus using corn-cobs and peanut hulls as substrates were evaluated. The results showed that the optimal conditions to produce cellulase included a 9-day fermentation period, an initial pH value of 6.0 at 30°C, a medium containing yeast extract as the nitrogen source. The inducer consisted of lactose or veratryl alcohol as the inducer. These conditions resulted in the highest level of enzyme activity. The production of cellulase was successfully achieved from P. sanguineus under optimal conditions (using corn-cobs as substrate, incubation at 30°C for 9 days with an initial pH value of 6.0, and containing yeast extract and veratryl alcohol). The results presented that FPase, CMCase and cellobiase activities of the crude enzyme were 8.492±0.702, 14.141±1.177 and 4.255±0.405 units per gram of substrate (U/gds), respectively. The crude enzyme was used to hydrolyze corn-cobs, coconut hulls, corn husks and peanut hulls (1.50 grams) by monitoring the decay at various times (0-96 h) using an enzyme volume of 10 ml (11.326 FPU/g substrate) in a solution of citrate buffer, a pH value of 4.8 at 50°C, a rate of shaking 160 rpm. Consequently, the amount of reducing sugars from the peanut hulls was highest (11.68±0.37 grams per liter), followed by corn cobs (10.15±0.43 g per liter) corn husks (8.35±0.12 g per liter) and coconut hulls, which displayed the lowest amount (5.45±0.47 g per liter), respectively, at 96 hours.