Biosurfactants in agriculture.

Agricultural productivity to meet growing demands of human population is a matter of great concern for all countries. Use of green compounds to achieve the sustainable agriculture is the present necessity. This review highlights the enormous use of harsh surfactants in agricultural soil and agrochemical industries. Biosurfactants which are reported to be produced by bacteria, yeasts, and fungi can serve as green surfactants. Biosurfactants are considered to be less toxic and eco-friendly and thus several types of biosurfactants have the potential to be commercially produced for extensive applications in pharmaceutical, cosmetics, and food industries. The biosurfactants synthesized by environmental isolates also has promising role in the agricultural industry. Many rhizosphere and plant associated microbes produce biosurfactant; these biomolecules play vital role in motility, signaling, and biofilm formation, indicating that biosurfactant governs plant-microbe interaction. In agriculture, biosurfactants can be used for plant pathogen elimination and for increasing the bioavailability of nutrient for beneficial plant associated microbes. Biosurfactants can widely be applied for improving the agricultural soil quality by soil remediation. These biomolecules can replace the harsh surfactant presently being used in million dollar pesticide industries. Thus, exploring biosurfactants from environmental isolates for investigating their potential role in plant growth promotion and other related agricultural applications warrants details research. Conventional methods are followed for screening the microbial population for production of biosurfactant. However, molecular methods are fewer in reaching biosurfactants from diverse microbial population and there is need to explore novel biosurfactant from uncultured microbes in soil biosphere by using advanced methodologies like functional metagenomics.

Isolation and characterization of indole acetic acid (IAA) producing Klebsiella pneumoniae strains from rhizosphere of wheat (Triticum aestivum) and their effect on plant growth.

The present study was undertaken for isolation of Klebsiella strains from rhizosphere of wheat (T. aestivum), screening and characterization of these strains for in vitro indole acetic acid (IAA) production and studying the effect of these strains on plant growth under gnotobiotic conditions. Nine strains of Klebsiella were isolated from rhizosphere of wheat (var. Lokwan) and identified as K. pneumoniae by 16S rRNA gene sequencing. Six K. pneumoniae strains showed in vitro IAA production. Colorimetric analysis showed that K8 produced maximum IAA (27.5 mg l(-1)) in the presence of tryptophan (1 mg ml(-1)) at 72 h of incubation with optimum conditions as pH 8.0, 37 degrees C and 0.5% (w/v) NaCl concentration. GC-MS analysis and IR studies confirmed presence of IAA in the cell filtrates of strain K8. Effect of six IAA producing Klebsiella strains on plant growth was studied by performing series of seed germination tests using moth bean seeds under axenic conditions and pot experiments using sterilized soil and wheat seeds (var. Lokwan). Strain K11 and K42 demonstrated increase in root length of inoculated moth beans (approximately 92.71% over the control). Results of pot experiments indicated that almost all the six IAA producing Klebsiella strains significantly increased the root length and shoot height of inoculated wheat seedlings over the control. The results suggest that these are promising isolates from wheat rhizosphere and merits research on appliance of these strains in agriculture.