ISOLATION AND CHARACTERIZATION OF ANTIMICROBIAL BACTERIAL ENDOPHYTES AGAINST FOODBORNE PATHOGENS FROM COFFEA ARABICA & COFFEA ROBUSTA FROM CHIKMAGALUR

Abstract

Endophytes are microorganisms that reside within plant tissues without causing any harm to the host. These non-pathogenic symbionts are known to produce various bioactive compounds, including antibiotics. Recent studies have emphasized the potential of endophytic bacteria in addressing the escalating threat of antibiotic resistance among pathogenic microorganisms. Chikmagalur, widely recognized as the birthplace of Indian coffee and known as the "Coffee Land of Karnataka," is renowned for the cultivation of Coffea arabica and Coffea robusta. In the present study sixteen bacterial endophytic isolates were obtained from different parts including root, stem, leaves and bark of Coffea arabica & Coffea robusta from Chikmagalur. The antimicrobial screening of the ethyl acetate extract of the isolates against foodborne pathogens, such as Salmonella typhi, Shigella, E. coli & Enterococcus faecalis was done using agar diffusion method. Eight out of sixteen endophytic bacterial isolates exhibited antimicrobial activity against the tested foodborne pathogens. Among them, two isolates CCRBI and CCRB2, both obtained from the bark of Coffea robusta demonstrated notably higher antimicrobial activity, showing larger zones of inhibition against Salmonella typhi, Shigella spp., and Escherichia coli. Consequently, these two potent isolates were selected for detailed morphological, biochemical, and phytochemical characterization.

Bioactive compounds were extracted from the liquid cultures of CCRBI and CCRB2 using ethyl acetate, and the resulting crude extracts were subjected to phytochemical analysis to identify the secondary metabolites. The ethyl acetate extract of CCRBI exhibited inhibition zones of 20.5 mm against S. typhi, 26.5 mm against Shigella, and 24 mm against E. coli. Similarly, CCRB2 showed inhibition zones of 20.5 mm, 21.5 mm, and 27 mm against the same pathogens, respectively. Phytochemical screening revealed the presence of alkaloids and saponins in the crude extracts, indicating their potential role in the observed antimicrobial activity.