Abstract

Corn cobs, an indigenous carbon source, were tested as substrate by Aspergillus niger for optimum synthesis of xylanase using the submerged fermentation technique. The trials for xylanase production were conducted at three concentration levels (2.5, 3.0 and 3.5%) of corn cobs, four different fermentation temperatures (25.0, 27.5, 30.0 and 32.5°C) and four various initial pH levels (5.0, 5.5, 6.0 and 6.5) of the culture medium for a period of 96 h. It was deduced from the study that the organism exhibited maximum enzyme activity (60.03 ± 1.83) at 3.0% corn cobs concentration, followed by 52.03 ± 1.21 and 50.07 ± 2.14 at 2.5 and 3.5% concentration, respectively at 30°C and 5.5 pH after a period 72 h of incubation. The comparison of the effect of various pH levels of culture medium showed that pH 5.5 had enhanced role in xylanase synthesis, as compared to other pH levels investigated in the study. Time scale analysis also revealed that a fermentation period of 72 h was best suitable for obtaining maximum yields of xylanase. Moreover, a temperature of 30°C was found to be optimum for higher yields of xylanase exhibiting the mesophillic behavior of the organism.

Key words: Xylanase, Aspergillus niger, corn cobs, mesophillic, biosynthesis, enzyme.