Cadmium resisting bacteria in Alexandria Eastern Harbor (Egypt) and optimization of cadmium bioaccumulation by Vibrio harveyi

Cadmium resisting bacteria (CRB) were present in all water and sediments (samples) collected from Alexandria Eastern Harbor, Egypt. The occurrences of CRB in sediments samples were higher than in water samples and reached up to 77.22% of total counts. Five isolates were selected to be the most resistant to cadmium with minimal inhibitory concentration of 60 ppm. The most potent isolate that accumulates a maximum Cd2+ concentration of 23.3 mg Cd2+/ g dry cells was identified as Vibrio harveyi. Medium components affecting metal removal by V. harveyi were explored based on the application of Plackett-Burman design. The growth of V. harveyi in the optimized culture conditions, recorded cadmium biosorption of 1.52 fold increase. Immobilized living cells of V. harveyi on hazelnut shells increased the uptake of cadmium to 49.35 mg Cd2+/g dry cells and removal efficiency up to 84%. Transmission electron microscope study confirmed the accumulation of Cd2+ by V. harveyi cells.Key words: Cadmium resisting bacteria, Vibrio harveyi, bioaccumulation, Plackett-Burman design

Optimization, economization and characterization of cellulase produced by marine Streptomyces ruber

Cellulase is a very important enzyme due to its great industrial applications. Six marine strains of actinomycetes were screened for their carboxymethyl cellulase (CMCase) productivity. Streptomyces ruber was chosen to be the best producing strain. The highest enzyme production (25.6 U/ml) was detected at pH 6 and 40°C after 7 days of incubation. Plackett-Burman design was applied to optimize the different culture conditions affecting enzyme production. Results showed that a high concentration of KH2PO4, and a low concentration of MgSO4 had a significant effect on enzyme production. Rice straw was used as a low cost source of cellulose. It was found that 30 g/l rice straw was the suitable concentration for maximum enzyme production. Partial purification of cellulase enzyme using an anionexchange chromatography resulted in the detection of two different types of CMCases, type I and II, with specific activity of 4239.697 and 846.752 U/mg, respectively. Moreover, estimation of their molecular weight revealed 27.0 kDa for cellulase type I and 24.0 kDa for cellulase type II. It could be concluded that S. ruber is a powerful cellulase producer strain under our tested experimental conditions.Key words: Cellulase production, Streptomyces ruber, Plackett-Burman design, rice straw, enzyme characterization

Bioremediation of acid fast red dye by Streptomyces globosus under static and shake conditions

Two different azo dyes known as acid fast red (AFR) and Congo red (CR) were examined for their decolorization by five strains of actinomycetes (Streptomyces globosus, Streptomyces alanosinicus, Streptomyces ruber, Streptomyces gancidicus, and Nocardiopsis aegyptia) under shake and static conditions. Streptomyces globosus decolorized AFR by 81.6% under static condition while 70.2% dye removal was achieved under shake conditions. Application of Plackett-Burman statistical design revealed that the main factors that affected biosorption capacity were the starch concentration and the inoculum size. Under static conditions, increasing the inoculum size and decreasing starch concentration increased the biosorption % up to 1.14 fold with time reduction, while increasing both the inoculum size and starch concentration under shake conditions increased the biosorption % up to 1.09 fold only. A trial for the use of potato peel for more economic biomass production of S. globous was carried out and (2 g/50 ml) and dried potato peel had the optimum concentration for maximum biomass production (0.3 g/50 ml) which led to considerable biosorption capacity (89.4%). Electron microscopy studies confirmed the dye removal.Key words: Azo dyes, Biosorption, Streptomyces globosus, Plackett-Burman design