Improved mannan-degrading enzymes' production by Aspergillus niger through medium optimization

The effect of different carbon and nitrogen sources on the production of mannan-degrading enzymes, focussing on beta-mannanase, by Aspergillus niger was investigated using shake flask culture. The beta-mannanase activity obtained during growth of A. niger on guar gum (GG, 1495 nkat mL(-1)) was much higher than those observed on other carbon substrates, locust bean gum (1148 nkat mL(-1)), alpha-cellulose (10.7 nkat mL(-1)), glucose (8.8 nkat mL(-1)) and carboxymethylcellulose (4.6 nkat mL(-1)). For fermentation using GG as a carbon source, bacteriological peptone gave the highest beta-mannanase activity (1744 nkat mL(-1)) followed by peptone from meat (1168 nkat mL(-1)), yeast extract (817 nkat mL(-1)), ammonium sulphate (241 nkat mL(-1)), ammonium nitrate (113 nkat mL(-1)) and ammonium chloride (99 nkat mL(-1)) when used as a nitrogen source. The composition of bacteriological peptone and initial pH of the medium were further optimized using response surface methodology (RSM). Medium consisted of 21.3 g L-1 GG and 57 g L-1 peptone with initial culture pH of 5.5 was optimum for beta-mannanase production (2063 nkat mL(-1)) by A. niger. The beta-mannanase production obtained in this study using A. niger was significantly higher than those reported in the literature.