Characteristics and Kinetic Study of 2-Hydroxypyridine Degradation by a Novel Bacterium Arthrobacter sp.2PR / 中国生物工程杂志

A novel strain,which could use 2-hydroxypyridine (2HP) as the sole source of carbon,nitrogen,and energy,was isolated from petroleum-contaminated soil at the Liaohe estuarine wetland.Strain 2PR was identified as Arthrobacter based on the morphology and 16S rRNA gene sequence.The optimum growth and degradation condition upon 2PR is 30℃ and pH 7.0,respectively.Under this condition,2HP degradation rate were 97.34％,94.95％,94.48％ and 89.21％ with 2,4,6 and 8 mg/ml initial concentration of 2HP at 42,96,120 and 156 h,respectively.Strain growth and 2HP degradation kinetics studies indicated that the strain followed Logisitic model,which could provide a theoretical and technical reference for the biodegradation of 2HP.The color of strain 2PR culture upon 2HP-MSN changed from colorless to blue,and then turned to brown.The blue pigment,which was observed at the culture of strain 2PR,was identified as 4,5,4',5'-tetrahydroxy-3,3'-diazadiphenoquinone-(2,2') by high performance liquid chromatography (HPLC) and high-performance liquid chromatography-mass spectrometry (LC-MS) analysis.The LC-MS signal with m/z =249.1 was observed in resting cells reaction sample with 2HP as the substrate.The degradation of 2HP might be achieved by a dioxygenase to produce 2,3,6-trihydroxypyridine,which could transformed to the blue pigment spontaneously,and then 2,3,6-trihydroxypyridine was converted with an pyridine-ring cleavage reaction.Among all the reported strains,strain 2PR has the strongest tolerance and the highest 2HP degradation efficiency at present.The strain has a promising application potential for 2HP waste treatment.

Evaluation of in vitro Reduction of Hexavalent Chromium by Cell-Free Extract of Arthrobacter sp. SUK 1201.

Aims: This study aims at to evaluate the hexavalent chromium [Cr(VI)] reduction potential of crude cell-free extracts of chromium resistant and reducing bacterium Arthrobacter sp. SUK 1201 and determination of optimum conditions for Cr(VI) reduction for possible bioremediation of Cr pollutants. Place and Duration of Study: Chromium reduction studies with Arthrobacter sp. SUK 1201, was undertaken in the Microbiology Laboratory, Department of Botany, University of Calcutta, Kolkata during 2010-2012. Methodology: Cell-free extract was prepared from freshly grown cell mass of Arthrobacter sp. SUK 1201 following the standard procedure. Cell mass suspended in Tris-HCl was sonicated (120 KHz for 30 min), centrifuged (12,000×g at 4ºC for 10 min) and the supernatant (S12) was used as the cell- free extract (CFE). Chromate reductase activity of the CFE was assayed colorimetrically using 1, 5-diphenylcarbazide as the complexing reagent. Results: Chromate reductase activity of CFE of Arthrobacter sp. SUK 1201 was constitutive in nature and reduced Cr(VI) with decreasing efficiency as the concentration of Cr(VI) was increased. Its Km and Vmax were 263.45 M Cr(VI) and 17.5 U mg-1 protein respectively. Reduction of Cr(VI) was optimal at pH 7 and 32ºC but was extremely thermolabile. NADH was the most suitable electron donor, and the chromate reduction was enhanced by Cu(II) and Fe(III), but inhibited by Hg(II). Among the different inhibitors tested, 2, 4-dinitrophenol (DNP) restored nearly 96.4% reductase activity, while carbonyl cyanidem- chloro phenyl hydrazone (CCCP) was most inhibitory to the process. Conclusion: It has been established that the Cr(VI) reduction potential of the cell-free extract of Arthrobacter sp. SUK 1201 is promising and could be exploited in the bioremediation of toxic hexavalent chromium.

Optimization of physical parameters for lipase production from Arthrobacter sp. BGCC#490.

The physical parameters for the production of thermostable, alkaline lipase from Arthrobacter sp. BGCC# 490 were optimized using response surface methodology (RSM), employing face centered central composite design (FCCCD). The design was employed by selecting pH, temperature and incubation period as the model factors and to achieve maximum yield, interaction of these factors was studied by RSM. A second-order quadratic model and response surface method showed that the optimum conditions for lipase production (pH 10.0, temperature 40oC and incubation period 48 h) resulted in 1.6-fold increase in lipase production (13.75 EUml-1), as compared to the initial level (8.6 EUml-1) after 48 h of incubation, whereas its value predicted by the quadratic model was 12.8 EUml-1. Lipase showed stability in the pH range 8-10 and temperature range 40-60oC, with maximum activity at pH 9.0 and temperature 50oC. Lipase activity was enhanced in the presence of K+, Ca2+ and Mg2+ ions, but inhibited by Hg2+ ions. The enzyme exhibited high activity in the presence of acetone, isopropanol and ethanol, but was unaffected by methanol. These properties suggest that the lipase may find potential applications in the detergent industry. The present work also demonstrated the feasibility of using experimental design tools to optimize physical parameters for lipase production by an indigenous Arthrobacter sp.

Isolation and Characterization of Atrazine-degrading Strains and Biotreatment Experiment of Industrial Wastewater / 微生物学通报

By using enrichment culture in liquid minimal medium or direct culture on minimal medium plates, thirteen bacterial strains (AD27-AD39) capable of utilizing atrazine as a sole nitrogen source for growth were isolated from a mixture of industrial wastewater and sludge from an atrazine manufacturing plant. Based on 16S rRNA gene sequencing, eleven strains were identified as Arthrobacter spp. and two strans were identified as Pseudomonas spp.. We further studied in detail the composition of atrazine-degrading genes and degradation characteristics of Arthrobacter sp. AD30 and Pseudomonas sp. AD39 that have high degradative activity. From PCR assays, it was indicated that both AD30 and AD39 strains contained atrazine-degrading genes trzN and atzBC and was capable of degrading toxic atrazine to nontoxic cyanuric acid. The biodegradation experiments showed that the percentage of atrazine removal were 92.5%,were 92.5%, 97.9% and 99.6% respectively after AD30, AD39 or the mixture of the two strains were inocu- lated and incubated at 30?C for 48 hours in minimal media containing 200 mg/L atrazine, indicating that atrazine degradation by the mixed bacteria was more effective than the single strain. In addition, after industrial wastewater containing 176 mg/L atrazine was inoculated with the mixed bacteria and incubated at 30?C with shaking for 72 hours atrazine were removed by 99.1%, implicating that the mixed bacteria are good candidate for biotreatment of atrazine-containing industrial wastewater.