Surfactants are widely used in modern industry, agriculture, environmental restoration, medicine, however, synthetic surfactants are environmentally hazardous substances. Advantages of products of microbial synthesis (biosurfactants) – high efficiency, stability in various temperatures and pH, biological activity, as well as biodegradability and low toxicity.
The strain R. erythropolis Au-1 (R. erythropolis UCM Ac-603) is a promising producer of cell-bound and extracellular trehalose lipid surfactants, exopolysacharides, cell polymers. The rational composition of the nutrient medium has been determined: hexadecane – 20 g/dm3, sodium nitrate – 3 g/dm3. The cultivation of bacteria R. erythropolis Au-1 for trehalose lipid surfactants synthesis has been carried out in a bioreactor with vortex aeration system (the yield of the target products increased by 41-50%).The possibility of waste vegetable oil using (phosphatide concentrate, oil sludge, waste frying sunflower oil) for the synthesis of trehalose lipid surfactants of R. erythropolis Au-1 has been established.
New approaches of extracellular trehalose lipids isolation with adsorbents were developed: sodium alginate or multilayer metal oxides based composite adsorbents (MnO, CoO, CuO). The use of ethanol for extraction of cell-bound trehalose lipid surfactants was justified (yield 0.29 g from 1 g biomass).
Physico-chemical and biological properties of the metabolites of Rhodococcus erythropolis strain Au-1 were established: high surface activity, emulsification of hydrophobic substances, wetting of surfaces as well as the influence on the permeability of cell membranes of microorganisms and plants, on the auxin phytohormones activity. The antimicrobial activity of surfactants against phytopathogen bacteria and fungi was shown. The highly effective formulations of trehalose lipid surfactants with thiosulfonates-biocides were designed. The biological properties of trehalosе lipid surfactants were established: increase the permeability of bacteria cell membranes (by 6-18%), adsorption of mineral elements by plants (by 27-48%), stimulate plant growth (by 20-36%). It has been shown that trehalose lipid surfactants promote the action of other biologically active substances, in particular, biocide-thiosulfonates (by 20-50%) and phytohormones – indolyl-acetic acid (almost 10 times). It was found, that trehalose lipid surfactants are less toxic than synthetic and some biogenic surfactants.
It have been substantiated that the cultural liquid supernatant (CLS) of R. erythropolis Au-1 is an effective and economically available plant growth regulater. Using the trehalose lipid surfactants increase the yield of legumes and cereals by an average of 20%. So, the possibility of practical use of metabolites in crop production has been proved.
