EXTRACELLULAR POLYMERIC SUBSTANCE (EPS) FROM KOCURIA SP. BRI 36: A KEY COMPONENT IN HEAVY METAL RESISTANCE

Objective: Evaluation of Extracellular Polymeric Substance (EPS) induced heavy metal tolerance in Kocuria sp. BRI 36.Methods: Initially, the effect of different concentrations of glucose (1-10 %) on EPS production by BRI 36 was examined. At optimum glucose concentrations, EPS levels were measured by varying heavy metal concentrations (10-50 ppm) of Pb2+, Cd 2+and Cr3+. Maximum tolerable concentration (MTC) and survival percentage of BRI 36 were determined under conditions that support EPS synthesis. Comparative analysis of extracted crude EPS was performed by Fourier Transform Infrared Spectroscopy (FTIR) to establish functional groups involved in the metal interaction. Results: Kocuriasp. BRI 36 produced maximum EPS (1g/l) at 5% glucose. Increase in EPS production up to 89% (considering 1g/l as 100%) with an increase in concentrations of heavy metals up to 40 ppm. MTC levels of BRI 36 for heavy metals increased up to 700 ppm when it was cultivated in presence of 5% glucose indicating a major role of surface polymer in metal adsorption. The function of EPS as a protective cover was also evident from an increase in survival percentage of BRI 36 up to 39.4 at MTC. Comparative analysis of extracted crude EPS by FTIR revealed the involvement of O-H, C=O, and C-O-C groups in metal adsorptionConclusion: Antarctic oceanic isolate Kocuria sp. BRI 36 has an ability to produced EPS under stress conditions of heavy metals. Simultaneously, its MTC values increased due to increase in EPS levels. These observations suggest the possibility to develop gentle, environmentally safe and cost-effective method for heavy metal removal

PRODUCTION AND CHARACTERIZATION OF EXOPOLYSACCHARIDE FROM MARINE MODERATELY HALOPHILIC BACTERIUM HALOMONAS SMYRNENSIS SVD III

Objective: To study 1) Optimization of nutritional and environmental parameters to enhance the yield of EPS by Halomonas smyrnensis SVD III isolated from seawater, West Coast of Maharashtra, India and 2) Purification and characterization of the EPS produced.Methods: The isolate was grown in Sehgal and Gibbons (SG) medium broth supplemented with 3% glucose, at 37 °C, 120 rpm for 7 d. Optimization of different parameters was carried out with one factor at a time approach. EPS was isolated from cell-free supernatant of the culture broth by centrifugation and precipitation using chilled ethanol, after removal of proteins by trichloroacetic acid (TCA) treatment. Characterization of the purified EPS was carried out with respect to fourier-transform infrared (FTIR) spectrum, 1H nuclear magnetic resonance (NMR) spectrum and mass spectrometry (MS) analysis.Results: Two-fold increase in the yield of EPS (23 g/l) by the selected isolate was obtained by using culture conditions as 10% inoculum size having cell density of 107 cells/ml, pH 6, incubation temperature 45 °C, 3% carbohydrate, 0.5% yeast extract as nitrogen source, 20% salt concentration and 7 d of incubation period. Characterization of the purified EPS suggested the presence of dominated glycosidic linkages and heptasaccharide nature of the molecule. As the present strain is halophilic, 20% NaCl was found to be optimum.Conclusion: Optimization studies resulted in two-fold increase in the yield of EPS which is of heptasaccharide nature

Short Circuit Current calculation in Distribution Networks with Connected Photovoltaic Plants

U ovome radu obrađena je problematika proračuna struja kratkoga spoja u distributivnim mrežama s priključenim fotonaponskim elektranama. U prvome dijelu rada napravljen je teorijski opis proizvodnje električne energije pomoću tradicionalnih sinkronih generatora i pomoću fotonaponskih modula. U drugome poglavlju detaljno je obrađen proračun struja kratkog spoja prema normi IEC 60909. Nakon teorijskog uvoda u prvome poglavlju, u trećem poglavlju glavnog dijela rada opisano je ponašanje sinkronih generatora i FN elektrana prilikom kratkih spojeva u mreži. U posljednjem poglavlju napravljene su simulacije trofaznih i jednofaznih kratkih spojeva u simulacijskom softveru DIGsilent PowerFactory, na ucrtanoj testnoj mreži. Rezultati simulacija prikazani su u tablicama i s prikladnim grafovima. Rezultati simulacija su očekivani i potvrđuju da fotonaponske elektrane ne pridonose značajno strujama kratkog spoja u distributivnim mrežamaIn this study has been proceeded the problem of calculating fault currents in distribution grids with photovoltaic units connected. In first part of this study, the theoretical explanation of producing electrical energy with traditional syncronous machines and photovoltaics was made. In second part, the calculating of fault currents with IEC 60909 norm was proceeded. After the theoretical explanations in first part, in third part of study, the behavior of syncronous machines and photovoltaics during the faults in grid was theoreticaly explained. In the last part of study, there were made a different simulations of 3-phase and 1-phase faults in distribution test grid, simulated with DIGsilent PowerFactory simulation software. The results of simulations have been shown in tables and graphs. Results of simulations are as expected, and they confirm that photovoltaics don't have a large contribution in distribution fault currents

Invitro synergistic activity of lactic acid bacteria against multi-drug resistant staphylococci

Abstract Background Multi-drug resistance in microorganisms is a serious problem at national as well as at a global level. Many researches have suggested alternatives to antibiotics with minimal or no major side effects. LAB is one of the most human-friendly probiotic strains known to mankind from times immemorial. With the objective to deal with progressing antibiotic resistance among microorganisms, the present work demonstrates the inhibitory activity of LAB consortium against MDR clinical isolates. Methods Total of nine hospital isolates of staphylococci were obtained and distinguished as S.aureus and coagulase-negative Staphylococcus (CoNS) based on their ability to ferment mannitol and form clumping with citrated plasma. All the test organisms were tested for antibiotic sensitivity with HiMedia (India) Octadisc Combi 92. Sets of L .plantarum, L .acidophilus and L.casei var. rhamnosus were prepared and tested against a standard culture of S.aureus NCIM 2129 by agar well diffusion method. To identify the primary source of substances responsible for inhibitory action, whole broth, cell-free supernatant, and cell lysate was prepared from the above-mentioned set. These were tested for their inhibitory action initially against standard S.aureus NCIM 2127, followed by clinical isolates. Results The antibiotic sensitivity profile revealed that all clinical isolates were multi-drug resistant. The maximum inhibitory potential was seen in a combination of the three LAB in the ratio 1:1:1. Highest antagonistic activity was observed with whole broth and cell lysate of LAB consortium. In liquid broth assay, the cell lysate of LAB consortium astoundingly exhibited up to 85% inhibition of multi-drug resistant Staphylococcus isolates. Conclusions Our results suggest antagonistic role of LAB metabolites against methicillin resistant staphylococci

Increase in production of biosurfactant from Oceanobacillus sp. BRI 10 using low cost substrates

The Antarctic isolate Oceanobacillus sp. BRI10 producing biosurfactant(BS) was cultivated in media containing different low cost carbon and nitrogen sources. Initially glucose in basal salt medium was replaced individually with sugarcane juice, whey and local commercial table sugar. Maximum emulsification index (E24) of 67.4% was obtained with sugarcane juice. Further, effect of various nitrogen sources was examined on BS production. Among them sodium nitrate was found to be the most suitable compound. E24 increased to 68.74% in the presence of sugarcane juice and sodium nitrate. The yield of biosurfactant in this medium was 14.25g l-1. The chemical characterization of biosurfactant revealed its glycolipoprotein nature consisting of lipids, carbohydrates, and proteins in the ratio of 4:94:2. Our results indicate a 14-fold increase in the yield and eight times decrease in the cost of production without major difference in the chemical nature of the biosurfactant, with respect to control. This is a significant result with regards to scale-up studies, recovery, and application

PRODUCTION AND PARTIAL CHARACTERIZATION OF PIGMENTS PRODUCED BY KOCURIA SP BRI 36: INFLUENCE OF HEAVY METALS

Objective: To study the production of pigments by Kocuria sp. BRI 36, their characteristics and influence of heavy metals on pigments.Methods: The effects of various physical and chemical parameters on pigments production by Kocuria sp. BRI 36 were examined. Pigments were extracted and partially characterised by Thin Layer Chromatography (TLC) and Fourier Transform Infrared Spectroscopy (FTIR). The effects of heavy metals such as Pb2+, Cd 2+, Ni2+ and Cr3+ were studied on pigment production. Antimicrobial activity and stability studies of crude pigment were also conducted.Results: Kocuria sp. BRI 36 isolated from cold oceanic region maximally produced red-orange pigment in presence of glucose (5% w/v) and protease peptone (0.2% w/v) at pH 7.5, 10±1 °C. Thin layer chromatography (TLC) analysis revealed the occurrence of three different compounds in the crude pigment belonging to carotenoid and xanthophyll group. Metals like Ni2+ and Cr3+ adversely affected pigment production while Pb2+and Cd2+enhanced the yield. The significant features of Kocuria sp. BRI 36 pigment are i) antimicrobial activity against Gram-positive and Gram-negative bacteria, ii) maximum stability at pH 7.5 and 10±1 °C and iii) ~38% color loss at 50±1 °C in 5 h.Conclusion: Our results suggest application potential of Kocuria sp. BRI 36 pigments in various biotechnological fields

Characterization of novel extracellular protease produced by marine bacterial isolate from the Indian Ocean

Out of the vast pool of enzymes, proteolytic enzymes from microorganisms are the most widely used in different industries such as detergent, food, peptide production etc. Several marine microorganisms are known to produce proteases with commercially desirable characteristics. We have isolated nine different cultures from marine samples of the Indian Ocean. All of them were i) motile ii) rod shaped iii) non spore forming iv) catalase and amylase positive v) able to grow in presence of 10 % NaCl. They produced acid from glucose, fructose and maltose and grew optimally at 30 0C temperature and pH 7.0-8.0. None of them could grow above 45 0C and below 15 0C. Only one of them (MBRI 7) exhibited extracellular protease activity on skim milk agar plates. Based on 16S rDNA sequencing, it belonged to the genus Marinobacter (98% sequence similarity, 1201 bp). The cell free extract was used to study effects of temperature and pH on protease activity. The optimum temperature and pH for activity were found to be 40 0C and 7.0 respectively. The crude enzyme was stable at temperature range of 30-80 0C and pH 5.0-9.0. It retained 60 % activity at 80 0C after 4 h and more than 70 % activity at 70 0C after 1 h. D value was found to be 342 minutes and 78 minutes for 40 0C and 80 0C respectively. Interestingly the enzyme remained 50 % active at pH 9.0 after 1 h. Comparison with other proteases from different microbial sources indicated that the neutral protease from the halotolerant marine isolate MBRI 7 is a novel enzyme with high thermostability

Isolation and cellular fatty acid composition of psychrotrophic Halomonas strains from Antarctic sea water

Microorganisms from extreme environments such as Arctic, Antarctic and Polar regions modulate their membrane fatty acids to survive in such habitats. Characterization of such microorganisms helps in understanding their physiological behavior. In view of this, the present article describes isolation, characterization and cellular fatty acid composition of three bacterial isolates from Antarctic sea water samples. All the three isolates (BRI 6, 29 and 31) were psychrotrophic Gram negative rods. Their 16S rRNA sequencing (around 1200 bp) revealed that all three of them belong to genus Halomonas. Each of them showed 99% sequence similarity to Halomonas neptunia Eplume1 (NR 027218), H. boliviensis LC1 (NR 029080) and H. variabilis DSM 3051 (NR 042068). The fatty acid analysis of our isolates indicated i) predominance of C 18:1, C 16:0 and C16:1 fatty acids and absence of trans fatty acids in all of them and ii) higher percentage of anteiso fatty acids than of iso fatty acids in BRI 6. These characteristic features may contribute to their adaptation to the Antarctic habitat