Optimization of Cultural Parameters for Cost Effective Production of Kojic Acid by Fungal Species Isolated from Soil

Abstract

A novel isolate capable of producing opulent yields of kojic acid with surface fermentation was screened from ten different isolated soil fungi. The organism was confirmed as Aspergillus flavus FJ537130 strain using 18SrRNA based molecular analysis and it was identified as a negative producer of aflatoxin. Though twelve different carbon sources were used, significant yields of kojic acid crystals was noticed with Sago starch. The optimized conditions established were substrate concentration 1000 ml (100 g of starch powder in 1000 ml of H2O), pH 6.0, Time 28 d, Temperature 28°C, Peptone concentration 4 g/l, KH2PO4 concentration 1 g/l, MgSO4 concentration 0.5 g/l and the yield achieved was 28.5 g/l. The resulted fermentation broth was subjected to solvent extraction followed by gel filtration for the separation of kojic acid and crystallization. The structural characterization of purified kojic acid was confirmed by Proton NMR, FTIR and XRD. The molecular weight and purity of kojic acid was confirmed by LC/MS and HPLC. The isolated kojic acid crystals shows high antimicrobial activity against pathogenic bacteria Staphylococcus aureus and Escherichia coli and maximum zone of inhibition was 9 mm. The inhibitory effect of kojic acid was more on the cell line K562 (Leukemia) when compared to the MDAMB435S (Breast cancer) cell line.