Comparative Evaluation of Rapid Screening Assays for Biosurfactant‐Producing Bacteria From Diverse Environments
TL;DR
ODA is highlighted as a more reliable and functionally relevant primary screening tool for identifying potent biosurfactant producers from both polluted and pristine environments.
Abstract
Biosurfactants are surface‐active compounds synthesized by microorganisms that serve as eco‐friendly alternatives to synthetic surfactants in industrial and environmental applications. This study compared four common screening assays—hemolysis, oil displacement (ODA), drop collapse, and emulsification index (E24)—to evaluate biosurfactant‐producing bacteria from diverse habitats. A total of 154 morphologically distinct isolates were obtained from oil‐contaminated soil, kitchen chimney soot, Himalayan alpine soil, and Southern Ocean sediments. Contaminated samples showed higher microbial loads (up to 2.64 × 10 8 CFU/g) and a greater frequency of positive strains. Hemolysis yielded the highest positives (56.4%), followed by ODA (26%), drop collapse (22.7%), and E24 (19.5%). Fifteen isolates (9.7%) were positive across all tests, with four strains (HUS20, BS108, SOE17, and KC15) exhibiting strong emulsification activity (53%–60%). 16S rRNA gene analysis identified these key producers as members of the genera Pseudomonas , Cytobacillus , and Streptomyces , underscoring the taxonomic diversity of efficient biosurfactant‐producing bacteria. Statistical analysis indicated a positive but statistically non‐significant correlation between microbial abundance and biosurfactant activity ( r = 0.69, p = 0.31). The findings highlight ODA as a more reliable and functionally relevant primary screening tool for identifying potent biosurfactant producers from both polluted and pristine environments.