Microbial Surfactants and Their Significance in Agriculture
Plant health and crop productivity need to be monitored to maintain the quality and availability of food to meet the growing demands of the population worldwide. Continuous efforts by researchers and scientists have explored novel bacteria and their metabolites (green compounds) to achieve sustainability in agriculture. Green surfactants produced by bacteria, actinomycetes, yeast, and fungi are less toxic and eco-friendly and have significant application in agriculture. Both epiphytic and endophytic plant-associated microbes are known to produce biosurfactants and have a vital role in motility, signaling, and biofilm formation. Biosurfactants aid in seed germination, inhibit phytopathogens and act as biocontrol agents used for bioremediation of contaminated soils, mobilize nutrients and enhance plant-microbe interactions. Based on their physicochemical properties, biosurfactants are glycolipids, lipopeptides, phospholipids, and polymeric. These biosurfactants are produced from renewable resources and exhibit excellent surface activity, possess high specificity, and are effective under extreme conditions. Here we report the isolation of bacteria from different rhizosphere samples and their screening for plant growth-promoting (PGP) traits and antifungal activity. Ten bacterial isolates exhibited PGP traits, antifungal activity, and biosurfactant activity. Two potential isolates (Pseudomonas aeruginosa DR 1 and Bacillus amyloliquefaciens RHNK 22) were selected for production of biosurfactant using synthetic media (nutrient broth, Bushnell has broth and mineral salt). Characterization of biosurfactant revealed it as rhamnolipid by DR 1 and surfactin and iturin by RHNK 22. Extracted biosurfactants (rhamnolipid and iturin) were evaluated for antifungal studies against Fusarium oxysporum f. sp. ricini, and fungistatic activity was around 40 μgmL−1 (with iturin) and 600 μgmL−1 (with rhamnolipid) and hence can be recommended toward their application as biocontrol agents.
KeywordsBiosurfactant Plant growth promotion Antifungal activity
Author (MYK) acknowledges the financial assistance received from the Department of Science and Technology, Government of India, for Project No. SR/FT/LS-17/2011.
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