Optimization of physiological growth conditions for maximal production of l-asparaginase by fusarium species

Author(s): Anil Kumar Megavarnam, Savitha Janakiraman

Abstract

L-asparaginase is an enzyme which catalyzes the hydrolysis of amino acid L-asparagine to L-aspartic acid and ammonia. Due to its utility in pharmaceutical as well as food industries, there has been a paramount interest on the production of this enzyme using microbial sources. We have screened three hundred and sixty four soil fungi for L-asparaginase production utilizing a relatively simple and reliable dye based rapid screening method. Our screening yielded two Fusarium species which showed appreciable amount of enzyme activity which were identified as Fusarium culmorum and Fusarium brachygibbosum by 18s rRNA coding nucleotide sequences. The physiological parameters for these two isolates were optimized for maximal production of the enzyme under laboratory culture conditions. The results revealed that Fusarium culmorum and Fusarium brachygibbosum showed maximum production of enzyme at shaking condition at 120rpm; temperature 30ºC and at 1% substrate concentration. Fusarium culmorum showed maximal enzyme activity at pH 7.5 whereas, Fusarium brachygibbosum showed maximal enzyme activity at pH 6.0.Citric acid, ammonium chloride, CaCl2 and glutamine enhanced the production of L-asparaginase in Fusarium culmorum, whereas, sucrose, FeS04 and arginine enhanced the activity of L-asparaginase in Fusarium brachygibbosum. However, sorbitol, yeast extract, casein, lysine and glycine repressed the production of L-asparaginase in both species of Fusarium.

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