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Chlorophenols are widespread and of environmental concern due to their toxic and carcinogenic properties. Development of less costly and less technically challenging remediation methods are needed; therefore, we developed a formulation based on micronized vermiculite that, when air-dried, resulted in a granular product containing the 4-chlorophenol (4-CP)-degrading Gram-positive bacterium Arthrobacter chlorophenolicus A6. This formulation and stabilization method yielded survival rates of about 60% that remained stable in storage for at least 3 months at 4 °C. The 4-CP degradation by the formulated and desiccated A. chlorophenolicus A6 cells was compared to that of freshly grown cells in controlled-environment soil microcosms. The stabilized cells degraded 4-CP equally efficient as freshly grown cells in two different set-ups using both hygienized and non-treated soils. The desiccated microbial product was successfully employed in an outdoor pot trial showing its effectiveness under more realistic environmental conditions. No significant phytoremediation effects on 4-CP degradation were observed in the outdoor pot experiment. The 4-CP degradation kinetics from both the microcosms and the outdoor pot trial were used to generate a predictive model of 4-CP biodegradation potentially useful for larger-scale operations, enabling better bioremediation set-ups and saving of resources. This study also opens up the possibility of formulating and stabilizing also other Arthrobacter strains possessing different desirable pollutant-degrading capabilities. [ABSTRACT FROM AUTHOR]

This study aimed to clarify the initial 4-chlorophenol (4-CP) biodegradation pathway promoted by a two-component flavin-diffusible monooxygenase (TC-FDM) consisting of CphC-I and CphB contained in Arthrobacter chlorophenolicus A6 and the decomposition function of CphC-I. The TC-FDM genes were cloned from A. chlorophenolicus A6, and the corresponding enzymes were overexpressed. Since CphB was expressed in an insoluble form, Fre, a flavin reductase obtained from Escherichia coli , was used. These enzymes were purified using Ni 2+ -NTA resin. It was confirmed that TC-FDM catalyzes the oxidation of 4-CP and the sequential conversion of 4-CP to benzoquinone (BQN) → hydroquinone (HQN) → HQL. This indicated that CphC-I exhibits substrate specificity for 4-CP, BQN, and HQN. The activity of CphC-I for 4-CP was 63.22 U/mg-protein, and the Michaelis-Menten kinetic parameters were v max = 0.21 mM/min, K M = 0.19 mM, and k cat / K M = 0.04 mM −1 min −1 . These results would be useful for the development of a novel biochemical treatment technology for 4-CP and phenolic hydrocarbons. [ABSTRACT FROM AUTHOR]

In this study, cphC-I and cphB, encoding a putative two-component flavin-diffusible monooxygenase (TC-FDM) complex, were cloned from Arthrobacter chlorophenolicus A6. The corresponding enzymes were overexpressed to assess the feasibility of their utilization for the oxidative decomposition of 4-chlorophenol (4-CP). Soluble CphC-I was produced at a high level (∼50%), and subsequently purified. Since CphB was expressed in an insoluble form, a flavin reductase, Fre, cloned from Escherichia coli was used as an alternative reductase. CphC-I utilized cofactor FADH 2 , which was reduced by Fre for the hydroxylation of 4-CP. This recombinant enzyme complex exhibited a higher specific activity for the oxidation of 4-CP (45.34 U/mg-protein) than that exhibited by CphC-I contained in cells (0.18 U/mg-protein). The Michaelis-Menten kinetic parameters were determined as: v max = 223.3 μM·min −1 , K M = 249.4 μM, and k cat /K M = 0.052 min −1 ·μM −1 . These results could be useful for the development of a new biochemical remediation technique based on enzymatic agents catalyzing the degradation of phenolic contaminants. [ABSTRACT FROM AUTHOR]

Bromophenol is listed as priority pollutant by U.S. EPA, however, there is no report so far on its removal in mixed pollutants system by any biological reactor operated in continuous mode. Furthermore, bromophenol along with chlorophenol and nitrophenol are usually the major constituents of paper pulp and pesticide industrial effluent. The present study investigated simultaneous biodegradation of these three pollutants with specially emphasis on substrate competition and crossed inhibition by Arthrobacter chlorophenolicus A6 in an upflow packed bed reactor (UPBR). A 2 full factorial design was employed with these pollutants at two different levels by varying their influent concentration in the range of 250-450 mg l. Almost complete removal of all these pollutants and 97 % effluent toxicity removal were achieved in the UPBR at a pollutant loading rate of 1707 mg l day or lesser. However, at higher loading rates, the reactor performance deteriorated due to transient accumulation of toxic intermediates. Statistical analysis of the results revealed a strong negative interaction of 4-CP on 4-NP biodegradation. On the other hand, interaction effect between 4-CP and 4-BP was found to be insignificant. Among these three pollutants 4-NP preferentially degraded, however, 4-CP exerted more inhibitory effect on 4-NP biodegradation. This study demonstrated the potential of A. chlorophenolicus A6 for biodegradation of 4-BP in mixed pollutants system by a flow through UPBR system. [ABSTRACT FROM AUTHOR]