Effect of Rhamnolipids on Pathogenicity Characteristics of Microorganisms in Organic Compost

Rhamnolipids are hydrophilic glycolipids, often classified as biosurfactants. They are produced by different bacterial species. Rhamnolipids are extensively studied in biological research because of their interesting features like antimicrobial, antifungal, and antiviral activities.

To study the antimicrobial effect of rhamnolipid, we conducted a crosssectional study on the eight different pathogenic bacterial strains from November 2019 to June 2020. These bacterial strains were isolated from the organic compost. Both disk diffusion and broth microdilution methods were used to evaluate the inhibitory effects of rhamnolipids on these pathogenic bacteria. Also, protease and amylase enzyme activities were evaluated in these eight bacterial isolates.

For Bacillus stearothermophilus, within the area of 31.5 mm, no growth was observed, hence proving the inhibitory effect of rhamnolipid. After calculating the minimum inhibitory (MIC) and minimum lethal concentrations (MLC) for each bacterial strain, it has been found that the studied bacteria were more susceptible to rhamnolipids than most of the antibiotics. Strains were also quantified for their enzymatic activity of proteases and amylases. The bacterial strains of Bacillus stearothermophilus, Brevibacillus brevis, Bacillus licheniformis, and Bordetella petrii showed maximum protease activity. Whereas Escherichia coli, Enterococcus faecalis, Enterobacter aerogenes, and Pseudomonas aeruginosa showed high amylase activity.

Rhamnolipids can be used as a potential antimicrobial agent for treatment of infections.