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Exopolysaccharides (EPS) of microbial origin is a promising alternative to chemical flocculants due to their sustainability and eco-friendly nature. In the present study, EPS produced by Bacillus cereus SK was studied and their flocculating activity was investigated. On incubation for 48 h, B. cereus SK produced 0.919 6 0.022 g/L of EPS from a cell mass of 3.59 6 0.06 g/L. The isolated EPS was identified as glycoprotein and chemical characterization by FTIR spectroscopic analysis suggested the presence of hydroxyl, amino and carboxyl groups. The kaolin clay flocculating activity of 83.4% was obtained on treatment with 12 mg/L of EPS. At 30% (v/v) of EPS 31.22 6 4.71 mL/g of Sludge volume index (SVI) and 34.44 6 1.51 mL/g of algal flocculation was observed. The EPS produced by B. cereus SK was non-toxic and did not exert any adverse effect on Danio rerio even at a concentration of 800 mg/mL.

Pink pigmented facultative methylotrophs (PPFMs) are diversified group of microorganisms that promote plant growth by producing indole acetic acid (IAA) and cytokinins. The objective of the present study is to isolate and characterize methylotrophic bacteria from the phyllosphere of mustard plant (Brassica niagra) and to study their plant growth promotion in tomato (Lycopersicon esculentum L.). Bacteria were isolated from the phyllosphere and the conserved mxaF gene sequence was amplified. Production of IAA was determined by High Performance Thin Layer Chromatography (HPTLC) and further quantified by spectrophotometric analysis. Effect of seed bacterization with the bacterial isolate MM2 was studied for percentage seed germination, root and shoot length. Based on NCBI BLAST search of the mxaF sequence obtained, the bacterial isolate was identified as Methylobacterium extorquens MM2. The amount of IAA produced by M. extorquens MM2 was 6.16 μg/ml. M. extorquens MM2 significantly increased seed vigour index (SVI) in tomato plants. The SVI of the treated plant was 1462.56 ± 83.96 as compared to the control, 1019.94 ± 113.61. Foliar application of M. extorquens MM2 also contributed a substantial impact on growth of tomato plant. The bacterial isolate M. extorquens MM2 thus can be employed in the crops for sustainable agriculture.

The present study focuses on the microbial synthesis of zinc oxide nanoparticles (ZnO NPs) and evaluating the antimicrobial property on foodborne pathogens. The bacterial strain, Acinetobacter schindleri SIZ7 was isolated from the waste filling area of Sivakasi, Tamil Nadu, India. The biogenic synthesis of ZnO NPs was carried out at room temperature and under suitable, eco-friendly environment using culture supernatant of A. schindleri. The physico-chemical properties exhibited by the biogenic ZnO NPs were characterised using UV-Visible Spectrophotometry, Energy dispersive X-ray spectroscopy (EDS), High Resolution Transmission Electron Microscopy (HRTEM), Fourier Transformed Infrared spectroscopy (FTIR) and Thermogravitometric Analysis (TGA). The synthesized ZnO NPs are polydispersed and spherical in shape. The antimicrobial activity of ZnO NPs was investigated against foodborne pathogens, Staphylococcus aureus (MTCC 96), Escherichia coli (MTCC 739), Vibrio parahaemolyticus (MTCC 451) and Salmonella enterica (MTCC 9844). The prepared ZnO NPs exhibited strong antimicrobial activity against E. coli and S. enterica with a minimum inhibitory concentration of 100µg ml-1. Thus, the bacterial strain Acinetobacter schindleri SIZ7 could be used for simple, extracellular, non-hazardous and efficient synthesis of antimicrobial ZnO NPs.

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