Suitable conditions for xylanases activities from Bacillus sp. GA2(1) and Bacillus sp. GA1(6) and their properties for agricultural residues hydrolysis

Bacillus sp. GA2(1) and Bacillus sp. GA1(6) were isolated from soybean field in Khon Kaen province, Thailand. Crude enzymes from both isolates showed the activities of cellulase, xylanase, and mannanase at 37°C for 24 h. The highest xylanase activities of Bacillus sp. GA2(1) and Bacillus sp. GA1(6) were 1.58±0.25 and 0.82±0.16 U/ml, respectively. The relative xylanase activities from both strains were more than 60% at pH 5.0 to 8.0. The optimum temperature of xylanases was 50°C in both strains. The residual xylanase activities from both strains were more than 70% at 60°C for 60 min. Five agricultural wastes (AWs), namely coffee residue, soybean meal, potato peel, sugarcane bagasse, and corn cobs, were used as substrates for hydrolysis properties. The highest reducing sugar content of 101±1.32 µg/ml was obtained from soybean meal hydrolysate produced by Bacillus sp. GA2(1) xylanase.