title: Optimization of cultural conditions of Arthrobacter sp. Sphe3 for growth-associated chromate(VI) reduction in free and immobilized cell systems.
abstract: The current study aimed to characterize Arthrobacter sp. Sphe3 ability to reduce Cr(VI) in suspended cell cultures as well as in immobilized form using Ca-alginate beads. Adaptation studies in the presence of 5 mg L(-1) Cr(VI) showed a significant increase in specific growth rate from 0.25 to 0.3 h(-1) and bioremoval percentage from 64% to 94% (p<0.05), whereas Arthrobacter sp. Sphe3 could tolerate up to 50 mg L(-1) Cr(VI). Optimization of culture conditions resulted in complete reduction of 45 mg L(-1) Cr(VI) at 30 °C, pH 8 and 10 g L(-1) of glucose. High glucose concentrations helped at reducing (80±2.4)% of initial 100 mg L(-1) Cr(VI), whereas the bacterial strain could tolerate 850 mg L(-1) Cr(VI). Cr(III) formation was first evidenced by the appearance of a green insoluble precipitate in the medium. Cell biomass was successfully immobilized in Ca-alginate beads that were evaluated for their stability. Cell release was sharply decreased when 4% Na-alginate was used under non-shaking conditions. Biotransformation efficiency was enhanced when 25-50 mg cells mL(-1) Na-alginate from the exponential growth phase were collected and co-encapsulated with either 1% glucose and 0.5% (NH4)2SO4, or 1% LB medium. Immobilized biocatalyst could be reused up to 6 continuous cycles in the presence of 10 mg L(-1) Cr(VI), but its performance was lowered at higher metal concentrations comparing with free cells that significantly maintained their reducing ability up to 300 mg L(-1) Cr(VI).
authors.affiliation: Department of Chemical Engineering, Section of Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
authors.forename: M G
authors.initials: MG
authors.lastname: Ziagova
authors.forename: A I
authors.initials: AI
authors.lastname: Koukkou
authors.forename: M
authors.initials: M
authors.lastname: Liakopoulou-Kyriakides
mesh_terms: D000464:Alginates; D001173:Arthrobacter / Q000254:growth & development / Q000378:metabolism*; D018533:Biomass; D001711:Biotransformation; D018914:Cells, Immobilized / Q000378:metabolism; D002840:Chromates / Q000378:metabolism*; D002857:Chromium / Q000378:metabolism; D003470:Culture Media; D020723:Glucuronic Acid; D006603:Hexuronic Acids
chemical_list: D000464:Alginates; D002840:Chromates; D003470:Culture Media; D006603:Hexuronic Acids; D002857:Chromium; D020723:Glucuronic Acid
keywords: Alginate; Arthrobacter; Bioreduction; Chromium; Immobilization