Volume 15, Issue 1: 2025 - Article 173

Abstract
Amylase enzymes play a crucial role in starch processing industries as they break down polysaccharides to simple sugars. Amylases are produced by microbial organisms for industrial use. The use of microorganisms, especially fungal species, and the employment of low cost substrates such as agricultural products for amylase production serves as an economical means for obtaining the enzymes. Glucoamylase (C3009H4570N782O1012S13) is an exoenzyme that removes glucose units sequentially from the non-reducing ends of starch and oligosaccharides. Glucoamylase also cleaves the α-1, 6- and α-1, 3-bonds, although at a slower rate. Glucoamylase is used in the processed-food industry, fermentation technology, textile and paper industries. In the present study, Aspergillus niger was isolated and sub-cultured for the production of glucoamylase, using submerged fermentation process. An eleven-day experimental study was carried out to determine the day of peak glucoamylase activity and protein production. Glucoamylase activity was assayed using Bernfeld’s or 3, 5- dinitrosalicyclic acid (DNSA) method, while protein was determined using the Lowry’s method. Peak glucoamylase activity was obtained on the 6^th day of the submerged fermentation using guinea corn starch as a carbon source. The crude glucoamylase harvested on day six had an enzyme activity of 208.5459 μmol/min with a total protein estimation of 214.95 mg in 150 ml. The crude enzyme was subjected to ammonium sulphate precipitation using 70% ammonium sulphate saturation to precipitate protein with the highest glucoamylase activity, and gel filtration chromatography was then used to further purify the precipitate obtained from the ammonium sulphate precipitation, which gave activities of 125.82 μmol/min and 83.09038 μmol/min, respectively. The optimum pH for glucoamylase activity was 5.0. The high glucoamylase activity and optimum pH presents this enzyme as a potential alternative for industrial application.

Keywords: Aspergillus niger; Activity; Glucoamylase; pH; Specific activity.

How to cite this article:
Onunwa GE, Ezugwu AL, Chilaka F, David SC, Ike NM, Charles P and Nwachukwu AG (2025). Effects of pH on the activity of glucoamylase obtained from Aspergillus niger in a submerged fermentation process using guinea corn starch as carbon source. Journal of Veterinary and Applied Sciences, 15(1): 885 – 892.

*Correspondence: E-mail:     ebubechi.onunwa.235572@unn.edu.ng      Phone: +2348184391147

Effects of pH on the activity of glucoamylase obtained from Aspergillus niger in a submerged fermentation process using guinea corn starch as carbon source

Gideon E. Onunwa ¹ *, Arinze L. Ezugwu ^{1, 2}, Ferdinand Chilaka ¹, Solomon C. David ³, Nmesoma M. Ike ¹, Precious Charles ¹, Amarachi G. Nwachukwu <sup>4

1</sup> Department of Biochemistry, Faculty of Biological Sciences, University of Nigeria, Nsukka, Enugu State, Nigeria.
² Department of Genetics and Biotechnology, Faculty of Biological Sciences, University of Nigeria, Nsukka, Enugu State, Nigeria.
³ Department of Veterinary Physiology and Pharmacology, Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Enugu State, Nigeria.
⁴ Department of Microbiology, Faculty of Biological Sciences, University of Nigeria, Nsukka, Enugu State, Nigeria.

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