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  • Author: Adrian Matei x
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Abstract

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.

Preliminary case study on the environmental quality and life quality in the Romanian rural rudimentary communities

In the present study, our intention is to reveal the positive and negative aspects of living, in the rural communities appearing in Romania in the last 5-6 decades; often, these have occupied territories with astonishing natural landscapes, situated close to large rural settlements with a century-old history. If, from the perspective of the quality of the natural components of the environment, inside the perimeter of these settlements we can talk about extremely favorable habitat conditions, from the perspective of the access to utilities and technical facilities, we can identify a primitive, rudimentary lifestyle, whose only goal is most oftenly, the access of the minimum resources for subsistence. This case study has been made on two communities, situated at the contact between the Subcarpathians of Arges and the Iezer-Papusa and Leaota Mountains, respectively: the Gura Pravat village, a formal settlement, which extends along the left bank of the Argesel river, north of Namaiesti tourist village and an informal village situated on the left bank of the Dambovita river, inside the Complexe Reserve Cheile de la Cetateni.

Abstract

Silver nanoparticles (AgNPs) are nanomaterials obtained by nanotechnology and due to their antimicrobial properties have a major importance in the control of various species of bacteria, fungi and viruses, with applications in medicine, cosmetics or food industry. The goal of the paper was to present the results of the research carried out on rapid extracellular biosynthesis of silver nanoparticles mediated by culture filtrate of lactic acid bacteria Lactobacillus sp. strain LCM5 and to assess the antimicrobial activity. Analysis of transmission electron microscopy (TEM) micrographs evidenced that the size of AgNPs synthesized using culture filtrates of lactic acid bacteria strain LCM5 ranged between 3 and 35 nm diameter, with an average particle size of 13.84±4.56 nm. AgNPs presented a good dispersion, approximately spherical shape, with parallel stripes certifying crystal structure. Frequency distribution revealed that preponderant dimensions of biosynthesized AgNPs were below 20 nm (94%). Antimicrobial activity of AgNPs was variable depending on both species and group of test microorganisms (bacteria or fungi) involved. Diameter of growth inhibition zone of Aspergillus flavus and Aspergillus ochraceus caused by silver nanoparticles synthesized by lactic acid bacteria strain LCM5 were similar (12.39 ± 0.61mm and 12.86 ± 0.78 mm) but significant stronger inhibition was registered against Penicillium expansum (15.87 ± 1.01mm). The effectiveness of biosynthesized silver nanoparticles was more pronounced against Gram-negative bacteria Chromobacterium violaceum with larger zone of inhibition (18 ± 0.69 mm diameter) when compared to those from fungi. Results recommend the silver nanoparticles biosynthesized using culture filtrate of the lactic acid bacteria Lactobacillus sp. strain LCM5 for biotechnological purposes, as promising antimicrobial agents.