@article { ISI:000255190300006, title = {Hexavalent chromate reduction by immobilized streptomyces griseus}, journal = {Biotechnology Letters}, volume = {30}, number = {6}, year = {2008}, month = {JUN}, pages = {1005-1010}, publisher = {SPRINGER}, type = {Article}, address = {VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS}, abstract = {

Hexavalent chromium, which is a mutagen and carcinogen, was efficiently reduced by Streptomyces griseus. This activity was associated with the cell. Cr6+ reduction by free as well as immobilized cells was studied: cells in PVA- alginate had the highest ( 100\%) Cr6+ removal efficiency in 24 h with reduction rates similar to free cells. Immobilized cells completely reduced 25 mg Cr6+ l(-1) in 24 h. PVA- alginate immobilized cells could be reused four times to completely reduce 25 mg Cr6+ l(-1) in 24 h each time. Chromate in a simulated effluent containing Cu2+, Mg2+, Mn2+ and Zn2+ was completely reduced by PVA- alginate immobilized cells within 9 h.

}, keywords = {Chromate reduction, Immobilized cells, polyvinyl alcohol, Streptomyces griseus}, issn = {0141-5492}, doi = {10.1007/s10529-008-9662-0}, author = {Poopal, Ashwini C. and Laxman, Ryali Seeta} } @article { ISI:000262966200010, title = {Chromate reduction by PVA-alginate immobilized streptomyces griseus in a bioreactor}, journal = {Biotechnology Letters}, volume = {31}, number = {1}, year = {2009}, month = {JAN}, pages = {71-76}, publisher = {SPRINGER}, address = {VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS}, abstract = {

Microbial reduction of toxic Cr(6+) to the less toxic Cr(3+) is potentially a useful bioremediation process. Among the matrices tested for whole cell immobilization of an efficient chromate-reducing Streptomyces griseus strain, PVA-alginate was the most effective and was used for reduction of Cr(VI) in a bioreactor. Cr(6+) reduction efficiency decreased as Cr(6+) was increased from 2 to 12 mg l(-1) but increased with an increase in biomass concentration. However, increasing the flow rate from 2 to 8 ml h(-1) did not significantly affect Cr(6+) reduction. The reduction was faster in simulated effluent than in synthetic medium and complete removal of 8 mg Cr(6+) l(-1) from effluent and synthetic medium occurred in 2 and 12 h, respectively. Our results indicate that immobilized S. griseus cells could be applied for the large-scale bioremediation of chromate-containing effluents and wastewaters.

}, keywords = {Bioremediation, Chromate reduction, Immobilized cells, Polyvinyl alcohol-alginate, Streptomyces griseus}, issn = {0141-5492}, doi = {10.1007/s10529-008-9829-8}, author = {Poopal, Ashwini C. and Laxman, Ryali Seeta} } @article { ISI:000268967200075, title = {Studies on biological reduction of chromate by Streptomyces griseus}, journal = {Journal of Hazardous Materials}, volume = {169}, number = {1-3}, year = {2009}, month = {SEP}, pages = {539-545}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Chromium is a toxic heavy metal used in various industries and leads to environmental pollution due to improper handling. The most toxic form of chromium Cr(VI) can be converted to less toxic Cr(III) by reduction. Among the actinomycetes tested for chromate reduction, thirteen strains reduced Cr(VI) to Cr(III), of which one strain of Streptomyces griseus (NCIM 2020) was most efficient showing complete reduction within 24h. The organism was able to use a number of carbon sources as electron donors. Sulphate, nitrate, chloride and carbonate had no effect on chromate reduction during growth while cations such as Cd, Ni, Co and Cu were inhibitory to varying degrees. Chromate reduction was associated with the bacterial cells and sonication was the best method of cell breakage to release the enzyme. The enzyme was constitutive and did not require presence of chromate during growth for expression of activity. Chromate reduction with cell free extract (CFE) was observed without added NADH. However, addition of NAD(P)H resulted in 2-3-fold increase in activity. Chromate reductase showed optimum activity at 28 degrees C and pH 7 (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {Bioreduction, Chromate reductase, Hexavalent chromium, Streptomyces griseus}, issn = {0304-3894}, doi = {10.1016/j.jhazmat.2009.03.126}, author = {Poopal, Ashwini C. and Laxman, Ryali Seeta} }