Gabi-Mirela Matei, Sorin Matei, Elena Maria Drăghici and Marian Stoian
The presence of oil hydrocarbons and salts in soils has as consequence the poor growth of plants due to the low availability of nutrients caused by unappropriate water regime, increased soil toxicity and the deterioration of soil structure. The present research has as main purpose the improvement of the bean plants (cultivar UNIDOR) growth and to stimulate microbial activity in rhizosphere using various natural stimulators and fertilizers (AMALGEROL,VERMIPLANT, POCO, IGUANA and FORMULEX) in greenhouse experiments on oil-polluted soil from Icoana farm, Olt county. The total counts of microorganisms (heterotrophic aerobic bacteria and filamentous fungi) were estimated by dilution plate method. The global microbial activity was measured as soil respiration by substrate-induced respiration method. Total bean plants biomass accumulation significantly increased under the influence of natural stimulators and fertilizers added (excepting IGUANA) when compared to untreated control. The best results were recorded for VERMIPLANT. Natural products induced activation of physiological activities of soil microbiota reflected in increased values of CO2 released by respiration, lower levels of colonization with phytopathogenic species, the domination of fluorescent pseudomonads, actinomycetes and cellulolytic fungi, too. The particular aspect of paper circular chromatograms reflected qualitative differences between rhizosphere soils determined by the effect of treatments with natural stimulators and fertilizers.
Gabi Mirela Matei, Sorin Matei, Adrian Matei and Elena Draghici
Lactic acid bacteria are frequently utilized in food industry and they are also recognized as antimicrobial agents due to their capability to produce metabolites such as: organic acids, biosurfactants, bacteriocins, hydrogen peroxide, cyclic dipeptides, exopolysaccharides. The main goal of this paper was to present the results of the research carried out on the strain LCM2 of lactic acid bacteria isolated from brined cucumbers, for production of biosurfactants and to assess its antifungal properties. The emulsification capacity of biosurfactant was measured using kerosene as the hydrophobic substrate. The value of emulsification index E24 was 89.04% showing a high emulsification activity of the biosurfactant. The structural characterization of biosurfactant by TLC revealed its glycolipidic nature. Assay of the ionic charge established the anionic charge of the biosurfactant revealed by the presence of precipitation lines towards the cationic surfactant dodecyl-dimethyl-ammonium chloride. The biosurfactant presented antibiofilm activity with low adherence capacity, structural damages of the hyphal net, conidiophores and delays or lack of sporulation and decreased biomass accumulation in four mycotoxigenic Penicillium and Aspergillus isolates. Results of in vitro assays recommend the biosurfactant produced by the new lactic acid bacteria strain LCM2 for biotechnological purposes, as alternative antifungal agent in food industry.