Optimizing culture conditions for production of intra and extracellular inulinase and invertase from Aspergillus niger ATCC 20611 by response surface methodology (RSM)

Abstract The aim of this study was obtain a model that maximizes growth and production of inulinase and invertase by Aspergillus niger ATCC 20611, employing response surface methodology (RSM). The RSM with a five-variable and three-level central composite design (CCD) was employed to optimize the medium composition. Results showed that the experimental data could be appropriately fitted into a second-order polynomial model with a coefficient of determination (R2) more than 0.90 for all responses. This model adequately explained the data variation and represented the actual relationships between the parameters and responses. The pH and temperature value of the cultivation medium were the most significant variables and the effects of inoculum size and agitation speed were slightly lower. The intra-extracellular inulinase, invertase production and biomass content increased 10-32 fold in the optimized medium condition (pH 6.5, temperature 30 °C, 6% (v/v), inoculum size and 150 rpm agitation speed) by RSM compared with medium optimized through the one-factor-at-a-time method. The process development and intensification for simultaneous production of intra-extracellular inulinase (exo and endo inulinase) and invertase from A. niger could be used for industrial applications.

Effect of extrinsic and intrinsic parameters on inulinase production by Aspergillus niger ATCC 20611

Background: Inulinase is a versatile enzyme from glycoside hydrolase family which targets the beta-2, 1 linkage of fructopolymers. In the present study, the effect of medium composition and culture conditions on inulinase production by Aspergillus niger ATCC 20611 was investigated in shake-flasks. Results: The highest extracellular inulinase (3199 U/ ml) was obtained in the presence of 25 percent (w/v) sucrose, 0.5 percent (w/v) meat extract, 1.5 percent (w/v) NaNO3 and 2.5 mM (v/v) Zn2+, at initial pH of 6.5, temperature 35ºC and 6 percent (v/v) of spores suspension in the agitation speed of 100 rpm. Surfactants showed an inhibitory effect on enzyme production. The optimum temperature for inulinase activity was found to be 50ºC. TLC analysis showed the presence of both exo- and endo-inulinase. Conclusion: Sucrose, Zn2+, and aeration were found to be the most effective elements in inulinase production by A. niger ATCC 20611. TLC analysis also showed that the crude enzyme contained both endo and exo-inulinases. The strain is suggested as a potential candidate for industrial enzymatic production of fructose from inulin.