Bioactive exopolysaccharide from endophytic Bacillus thuringiensis SMJR inhibits food borne pathogens and enhances the shelf life of foods

Abstract

In recent times, the use of microbial exopolysaccharides as food preservative has gained significant industrial applications. Accordingly, in this study, EPS producing bacteria was isolated from mango leaf. The isolated bacteria were identified as B. thuringiensis strain SMJR by morphological characteristics and 16s rDNA sequencing. The 16s rDNA gene sequences were submitted to GenBank database under accession number MZ049561. The isolated B. thuringiensis strain SMJR strain was subjected to EPS production using basal salt medium. EPS was recovered and purified by ethanol precipitation. The anthrone test showed that EPS is a polysaccharide composed mainly of glucose. EPS was characterized by UV–Vis spectra and FTIR. UV–Vis spectra showed an absorbance peak at 230 nm indicating the presence of polysaccharides. FTIR revealed the presence of various functional groups stretching between 4000 and 200 cm-1. The antibacterial activity demonstrates that both the crude EPS and pellet possessed inhibitory activities against the tested food borne pathogens (E. coli and K. pneumoniae). The crude EPS showed greater antibacterial effects against the tested food borne bacteria when compared to the pellet. Furthermore, EPS has enhanced the shelf life of grape juice by preventing the growth of pathogenic bacteria. This study concludes that the EPS from B. thuringiensis strain SMJR could be used as a potential preservative to prevent the spoilage of food and emergence of food borne diseases.