Optimization of production conditions for xylanase production by newly isolated strain Aspergillus niger through solid state fermentation of oil palm empty fruit bunches

•Novel Aspergillus strain was identified as A. niger USMSD2 (GenBank acc. no-KU882054).•Parametric optimization of cultural terms improved xylanase production by 160%.•RSM cultural optimization without considering incubation period was validated.•Organic nitrogen sources enhanced xylanase production better than inorganic sources.•High conc. of N2 makes xylanase production by A. niger independent of its growth rate.

Response surface (RSM) optimization of selected cultural parameters and the effect of various nitrogen sources on xylanase production by novel strain of Aspergillus niger via solid state fermentation of oil-palm-empty-bunches (OPEFB) were assessed. The newly isolated oil-palm-field-domiciled strain of Aspergillus niger was identified based on rRNA analysis as Aspergillus niger USM SD2 (GenBank accession no. KU882054). RSM was used to generate regression model for xylanase activity by this organism; while the effect of non-inclusion of incubation period among selected cultural conditions was assessed based on the xylanase production profile of the organism after optimization. Results showed that optimization model terms were significant with regression coefficient (R2) value of 0.95. Xylanase activity was optimum at 25 °C, initial moisture-substrate ratio 4:1; pH 6.3 and total inoculums size, 2 × 106 spores/ml. At optimum production period, xylanase production was enhanced by more than 100% of its value prior optimization. Moreover, the use of yeast extract (Y/E) enhanced xylanase production better than any other nitrogen sources evaluated. Consequently, at its optimum concentration (15 g/l), the addition of Y/E enhanced xylanase production such that final activity (3246 IU/gds) was 160% and 29% higher than activities (1250 IU/gds) prior to and after (2512 IU/gds) parametric optimization respectively. Further analyses also showed that xylanase production by A. niger USM SD2 was independent of period of incubation and, hence, its growth rate.