Characterization of antifungal metabolites produced by Lactobacillus plantarum and Lactobacillus coryniformis isolated from rice rinsed water

Abstract

A recent spike in demand for chemical preservative free food has derived the scientific community to develop natural ways of food preservation. Therefore, bio-preservation could be considered as the great alternative over chemical ones owing to its potential to increase shelf-life and nutritional values of foodstuffs. In the present study, lactic acid producing bacterial species were isolated from rice rinsed water and identified by 16S rRNA gene sequencing as Lactobacillus plantarum BCH-1 (KX388380) and Lactobacillus coryniformis BCH-4 (KX388387). Antifungal metabolites from both Lactobacillus species were extracted by polarity-based solvents in which ethyl acetate showed remarkable antifungal activity against Aspergillus flavus and Aspergillus fumigatus by disc diffusion assay. Different organic acids and fatty acids have been identified by reversed-phase high-performance liquid chromatography (RP-HPLC) and gas chromatography-mass spectrometry (GC-MS) analysis, respectively. Lactic acid and citric acid were the major organic acids found in ethyl acetate fractions of L. plantarum and L. coryniformis, respectively. Similarly, 9,12-otadecadienoic acid (Z,Z)-methyl ester and hexadecanoic acid, methyl ester were the major fatty acids found in n-hexane fractions of L. plantarum and L. coryniformis respectively. Moreover, the isolation of novel antifungal metabolites from locally isolated Lactobacillus species was focused and it was revealed that organic acids are important contributors towards antifungal potential. A novel fatty acid (i.e. 12-hydroxydodecanoic acid) has also been explored and found as potential metabolite against filamentous fungi. Conclusively, various metabolites isolated from non-dairy source showed antifungal activity especially against Aspergillus species. Hence, these metabolites have been considered as a good choice for bio-preservation.

Keywords: 12-Hydroxydodecanoic acid; Aantifungal activity; Fatty acids; GC–MS; HPLC; Lactic acid bacteria; Organic acids.