Drop collapse assay on lotus leaf (Nelumbo nucifera): a simple and cost effective method for rapid detection of biosurfactants

Abstract

An alternative technique to perform drop collapse assay for rapid detection of surface active agents produced by microorganisms is described. The method is rapid, simple, economical and sensitive as it can detect the biosurfactant even in low concentrations. The limit of detection for Triton-X 100:0.01 mM (6.25 µg mL -1 ), CTAB: 0.1 mM (36.44 µg mL -1 ) and SDS: 0.001 mM (0.288 µg mL -1 ) using lotus leaf assay. This method uses Lotus (Nelumbo nucifera) leaf as the surface for performing drop collapse studies and can be useful as an initial step for screening microorganisms for biosurfactant production and for detection of surfactant activity. The underline principle was that the leaves of lotus are super hydrophobic, i.e. drops of water roll off free of residue. The lotus leaf has surface roughness and posses water-repellent wax crystals which attribute towards super hydrophobic properties. Hence, if surface active agent capable of reducing surface and interfacial tension acting as wetting agent is produced by the Microbispora sp. V2 even in low concentrations, the drop collapse will occur on lotus leaf and wetting of leaf can occur. Lotus leaf can be a better alternative to microtitre plates as due to its rapidity, sensitivity, simplicity, ease, cost effectiveness and reproducibility. The simplicity of this technique makes it suitable in rapid screening of large number of surfactant producing microbes without the need of expensive high throughput systems.

Bioremediation and Biodegrdation of Oil by Biosurfactants

“…Only biosurfactants producing organisms, form micro emulsion in this specific screening test. Meghamala et al [12] , used lotus leaf for the rapid detection of biosurfactants in drop collapse assay. Lotus leaf is different because of its surface roughness and the presence of the water repellent wax crystals exhibits the super hydrophobic nature of the leaf.…”

“…They also noticed the biosurfactant withstand at 120 0 c for 1 hour and resisted at 15% NaCl concentration. Luna et al [33] , reported Candida sphareica in the cell free broth stable at wide range of pH (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), stable 1 hour at extreme temperature 120 0 c and withstand at NaCl concentration of 10 %. In the present study, the biosurfactant produced by the isolate have the capability to withstand at wide elevated pH ranges, and not in acidic condition, because in acidic condition the biosurfactant can normally precipitated.…”

“…Surface roughness and water repellant wax crystals confer hydrophobic properties of leaf. [12] . A surface-active agent will reduce the surface and interfacial tension then eventually the drop is collapsed.…”

Biosurfactants from renewable sources - A review

“…If the drop of oil is found to rupture in 1 min, it indicates production of biosurfactant by microorganism. There is a report on the study of rapid detection of biosurfactants by drop collapse assay on lotus leaf (Nelumbo nucifera) (Waghmode et al, 2016).…”