Evaluation of the production of biosurfactant from halophilic bacteria isolated from salt pans in Hambantota, Sri Lanka

Abstract

Halophilic bacteria are salt-loving and, therefore, can thrive in high-salt environments. They have evolved physiologically and biochemically to survive in these extreme conditions. Recently, halophilic bacteria have gained attention due to their potential for producing biosurfactant—surface-active compounds with applications in environmental remediation, agriculture, and the pharmaceutical industry. This study evaluates the biosurfactant-producing ability of the halophilic bacteria isolated from saltpans in Hambantota, Sri Lanka. Sediment samples were collected from six Maha Lewaya salt pan ponds in Hambantota, Sri Lanka, each pond having different salt densities. Halophilic bacteria were isolated on halophilic agar and incubated for 48 hours at 30 °C. Morphologically and biochemically identified bacteria were named HA I, HA II, HA III, HA IV, and HA V. Biosurfactant-producing ability of the isolates was evaluated using different screening methods, i.e., cetyltrimethylammonium bromide agar (CTAB) assay, oil-displacement assay, foam formation, and estimation of emulsion index. In the CTAB assay, all five isolates produced blue halos while only four isolates showed stable foam formation. The oil displacement assay showed positive results for all five isolates, with different oil displacement capacities ranging from 0.60 to 7.33 cm clear zone diameter. Emulsification activity varied among the strains, where HA IV showed the lowest (10.33 %), and HA I showed the highest (46.43 %) emulsion index. According to these results, halophilic bacteria isolated in this study showed significant biosurfactant production abilities, with potential applications in bioremediation, oil recovery, and other industrial processes.