PRODUCTION OF KOJIC ACID FROM LEMON (Citrus limon) PEEL USING Aspergillus niger (PQ585363) AND Aspergillus flavus (PQ585407) IN SUBMERGED FERMENTATION

Document Type : Research article

Authors

1 Department of Microbiology, Faculty of Pure and Applied Sciences, Kwara State University Malete, Nigeria

2 Department of microbiology, pure and applied sciences, Kwara State University, Malete, Nigeria

Abstract

Kojic acid, valued for its antioxidant and antimicrobial properties, can be produced using lemon peels as a sustainable substrate. This study isolated and characterized fungi from lemon peels, identifying Aspergillus niger (PQ585363) and Aspergillus flavus (PQ585407) as kojic acid producers. The proximate composition of lemon peels revealed moisture (9.12%), protein (11.46%), fat (2.79%), and high carbohydrate content (55.61%). Fungi were isolated using standard procedures and characterized morphologically and molecularly. The isolates were screened for kojic acid production using 1% Ferric chloride solution. Aspergillus niger and Aspergillus flavus were positive, while Fusarium sp. screened negative.
Submerged fermentation was optimized using Response Surface Methodology (RSM), varying pH, incubation period, glucose, yeast extract, and substrate concentrations. Co-cultures of Aspergillus spp. yielded higher kojic acid concentrations (7.50 g/L) than single cultures of A. niger (6.99 g/L). Optimal fermentation conditions were determined as 150 g/L glucose, 6 g/L yeast extract, 96-hour incubation, and pH 5.0. Under these conditions, co-cultures produced 7.80 g/L kojic acid, while single cultures produced 7.40 g/L. Kojic acid was extracted using ethyl acetate, and its purity was assessed through FTIR spectroscopy, revealing a purity of 97.00%. This study demonstrates the potential of lemon peels as a viable substrate for kojic acid production through submerged fermentation with Aspergillus species.

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