Tellurite resistance and reduction during aerobic and anaerobic growth of bacteria isolated from sarcheshme copper mine

Tellurium compounds can be found in high concentrations in land and water near sites of waste discharge of industrial manufacturing processes and anodic sludge of copper mine. Potassium tellurite [K2TeO3] is toxic to many microorganisms at concentrations >1mg/mL. In this research, some species of facultative anaerobic bacteria [Bacillus sp.] were isolated from Sarcheshme copper mine[Kerman, Iran] which demonstrated high-level-resistance to tellurite and accumulation of metallic tellurium crystals. High-level-resistance was observed for Bacilli and cocci grown with certain organic carbon sources, implying that tellurite reduction is not essential to confer tellurite resistance. Level of adsorption was determined by inductively coupled plasma and spectrophotometer [Diethyldithiocarbamate method]. The level of tellurite concentration in the bacteria cell and the formation of tellurium nanocrystals were illuminated by transmission electron microscope and scanning electron microscope. The Te[0] crystals occur internally and each microorganism forms a distinctly different structure [for example Bacillus selenitreducens make tellurium nano rod]. In this study it was found that microorganism can grow 3.in 1500mg/L-2000mg/L and higher tellurite concentrations. The use of microorganisms to generate Te nanomaterials may be an alternative for bench-scale syntheses. Additionally, they may also generate products with unique properties unattainable by conventional physical/chemical methods. This study is important because native bacteria from Sarcheshme [Kerman, Iran] that may show high-level-resistance to tellurite, were isolated

Alginate biopolymer production by Azotobacter chroococcum from whey degradation

The potential of three Azotobacter chroococcum strains for whey degradation and alginate production were investigated. After dilution, samples were spread plated on isolation agar and Manitol agar and incubated at 30 °C for 24 h. Microorganisms were screened for their ability to whey degradation and alginate production based on colony morphology, negative and capsule staining, ability to decrease the apparent turbidity of the fermentation broths in batch and semi continuous culture by spectrophotometer assay at 400 nanometer and tensiometer assay. Of the three strains tested for whey degradation, only Azotobacter chroococcum 1723 produced significant apparent growth on whey broth and could decrease about 70% of turbidity in fermentation broth during 6 days in batch culture. Colonies of this strain was characteristically yellow, large, moucoid and slimy on whey agar than Manitol agar after 24 h at 30 °C. Transmission electron microscopy assay and Carbazole reagent were used to recognize the alginate biopolymer. After optimizing environmental factors such as pH, salt concentration and temperature, this strain was able to produce exopolysaccharide greater than 5 mg/mL. Optimum results were obtained when using whey broth as a fermentation medium without extra salt, temperature at 35 °C and pH 7. Increasing inorganic and organic nitrogen sources [yeast extract and NH[4]NO[3]] reduced whey degradation at least 30%. Transmission electron microscopy assay showed a net-structured polysaccharide capsule around the cells. Semi-continuous culture results demonstrated that, alginate production as well as whey degradation was decreased [1 mg/mL and 30%]

Production and recovery of poly- beta -hydroxybutyrate from whey degradation by azotobacter

Three strains of Azotobacter chroococcum were studied to produce poly- beta hydroxybutyrate as a inclusion body by whey degradation. Optimum degradation whey results were obtained when using whey broth as a fermentation medium without extra salt, temperature at 35°C and pH 7 [P<0.05]. Lambda max for whey broth medium was determined probably about 400 nm. The effect of different nitrogenous rich compounds [NH[4]NO[3], Bactopeptone, Casein, Yeast extract, Meat extract, Protease peptone and Tryptone] on whey degradation showed that incorporation of nitrogenous compounds into the medium did not increase whey degradation by Azotobacter chroococcum 1723 [P<0.05]. But poly- beta hydroxyl-butyrate production was increased in presence Meat extract up to 75% of the cell dry weight after 48h. The addition of nitrogenous sourced [except ammonium nitrate] had a positive effect on poly- beta hydroxyl-butyrate production as it peaked in the presence of Meat extract and 4.43 g/L was accumulated in comparison to 0.5g at diazotrophically growing cells. Increasing the O[2] values resulted by shaking at 122 rpm in decreased poly- beta hydroxyl-butyrate yield form 4.43 to 0.04 g/L. The results show that this medium supports the growth of strain 1735 and also that this waste could be utilized as a carbon and nitrogen source. Production of poly- beta hydroxyl-butyrate by using whey as a medium looks promising, since the use of inexpensive feed-stocks for poly- beta hydroxyl-butyrate is essential if bioplastics are to become competitive products