Improvement of Kojic Acid Production by a Mutant strain of Aspergillus flavus

Abstract

The ability of 58 different strains of Aspergillus, Mucor, and Penicillium to form kojic acid has been studied. Four Aspergillus species and Penicillium cryzogenum local isolates with high activity of kojic acid synthesis were screened for kojic acid production on five proposed kojic acid producing synthetic medium. Aspergillus flavus (AF) was found to be the highly active one for kojic acid production. The highest level of kojic acid productivity (0.234 g/ l.h) obtained by A. flavus using fermentation medium of 100g/l glucose, and 5.0 g/l yeast extract, and incubated at 30°C and 180rpm for 9 days. The study implicated the optimization of different carbon and nitrogen source of fermentation medium. Among the carbon sources tested, glucose gave the highest kojic acid yield (50.27 g/l) followed by sucrose (48.95 g/l). The use of 5g/l yeast extract resulted in the highest kojic acid production (50.21g/l) compared with the other nitrogen sources. Improvement of Aspergillus flavus by natural selection and random mutagenesis by using UV (for 5, 10, 20, 40 and 60 min) and various doses of gamma irradiation (20, 40, 60, 80, 100, 120, 140 and 160 Gy) has been done to obtain a potential mutant which produce kojic acid higher than its parent strain. Some of wastes hydrolyzates were used as carbon and nitrogen source, potato starch, and rice bran hydrolyzates were the best carbon and nitrogen source, respectively.

Key words: Kojic acid, Aspergillus flavus, mutation, UV, Gamma radiation