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Milk and milk products have been used by human population since ancient ages and have been a well known source of Lactobacilli. The beneficial effects of viable probiotic bacteria as dietary supplements have gained huge research interest, Lactobacillus spp. with probiotic characteristics are widely used to prepare fermented dairy products such as yoghurts, milk-shakes etc. The goal of the present study was to examine Lactobacillus species with potential activities, total four different companies of Yoghurt samples were collected from City market of Gulbarga region for isolation of probiotic Lactobacillus species. Among the samples, 32 lactic acid bacteria strains were isolated, thirteen (13/32) best Lactobacillus isolates were selected by preliminary screening as potential probiotics with antimicrobial activity against pathogenic bacteria. All the Lactobacillus isolates were then characterized in vitro for their probiotic characteristics and antimicrobial activities against pathogens. The isolates were resistant to NaCl (1–6%), bile salt (0.5–3%) and showed good growth in the acidic condition, while maximum growth was observed at pH around 6.0. All the isolates were susceptible to clinical antibiotics; also the isolates were exhibited effective aggregation and hydrophobicity studies. Based on the results, selected Lactobacillus isolates were considered as novel and potential probiotic bacteria. Thus, further extensive research on isolation and characterization of probiotic bacteria from local dairy products and their growth optimization might be necessity for development of probiotic enriched food supplement and human health benefits through prevention and controlling of bacterial infections. Keywords: Lactic acid bacteria, Lactobacilli, Yoghurt, Antimicrobial activity and dairy products, Bacteriocin

In the present investigation we report unique biological green synthesis of nanoparticles (AgNPs) by secondary metabolites of Streptomyces supernatant extract acting as reducing agents in hydrothermal process. Various divergent techniques like sonication, microven, heating and hydrothermal (autoclaving) techniques were employed to produce silver nanoparticles through microbe-mediated assistance. The Streptomyces sp. GUT 21 was isolated from the field soil sampled neighbouring the campus of Gulbarga University. Morphological and biochemical characterization of the strain was performed and its taxonomical genus identification was determined by 16s rDNA technique. The formation of nanoparticles was first monitored by measuring the surface plasmon resonance (SPR) band at 410 nm through UV–Visible absorption spectroscopy. FTIR analysis revealed that many efficient clusters of functional bio-molecules are playing significant role in capping and synthesis process during hydrothermal method. The crystalline structure of the AgNPs and the presence of elemental silver nanoparticles were confirmed by powder X-ray diffraction (PXRD) and scanning electron microscopy. Our results indicated that, nanoparticles are spherical in shape with an average of 23–48 nm in size. The biosynthesized AgNPs exhibited significant antibacterial activity against Escherichia coli (MTCC 9537), Klebsiella pneumoniae (MTCC 109), Pseudomonas aeruginosa (MTCC1688) and Staphylococcus aureus (MTCC 96). This biotechnological development of synthesis of nanoparticles can further be exploited as “new-generation of antimicrobials” against multi-drug resistant bacteria (MDR) for various medical diagnostic applications.

Multi drug resistant Klebsiella pneumoniae showed stepwise adaptation when grown in increasing concentration of Cefotaxime eventually reaching a maximum of 2 mg/ml. The resultant Cefotaxime resistant mutant strain was stable and did not revert to susceptibility on frequent subculturing. The response of the cells to different concentration of Cefotaxime was examined by scanning electron microscope which showed that the size of the bacterium increased with increasing concentration of Cefotaxime.