Studies of the Nutritional, Environmental Effects and Repressive Nature of Simple Sugars on the Production of endo-β-mannanase by Aspergillus flavus PT7 on Solid State Fermentation

Abstract

Aims: The importance of nutritional and environmental factors in the production of microbial enzymes cannot be overemphasized. Hence, endo-β-mannanase production was systematically studied in a step-wise approach of building up on the experimentally observed conditions favouring the production of this enzyme in Aspergillus flavus PT7. Place and Duration of Study: Department of Microbiology, University of Ibadan, Nigeria, between January 2018 and December 2018. Methodology: Thirty-eight (38) fungal isolates obtained were screened for mannolytic ability using standard method. The highest producer of endo-β-mannasase was subjected to various production conditions by adjusting the nutritional and environmental factors in view of optimizing the production of this enzyme in the isolate Aspergillus flavus PT7. Results: Copra meal was the highest inducer of mannanase production in the isolate at enzyme activity of 85.86±3.93 U/gds. Production increased to 94.54±0.42 when all forms of extraneous nitrogen sources were excluded from the production medium. pH 5.0, temperature 30°C, moisture content at 100% v/w and inoculum size of 8.0% v/w led to the increase in production by 44% (enzyme activity of 153.24±5.69 U/gds) in 5 days of incubation. Allowing the production set up additional two (2) days led to production increase with a recorded enzyme activity of 170.34±4.35 U/gds. Production of endo-β-mannanase in A. flavus PT7 was observed to be inductive as the presence of simple sugars like glucose, galactose, arabinose and xylose led to extended lag period in the production of the enzymes by the isolate. Conclusion: Production of endo-β-mannanase by Aspergillus flavus PT7 was successfully optimized in a step-wise and systematic experimental study of the nutritional and environmental growth conditions of the isolate.