Phenol pollution often associated with agriculture industries involving pesticides and respiratory inhibitors. Microorganism used for biodegradation of phenols should also be resistant to the pesticides and respiratory inhibitors. In this study, 1 ppm of carbofuran, paraquat dichloride, atrazine, potassium cyanide (KCN), sodium azide (NaN3) and rotenone were used to investigate the ability of Acinetobacter sp. strain AQ5NOL 1 freely suspended and immobilized in gellan gum beads to degrade phenol in the presence of pesticides and respiratory inhibitors. Results from this study showed that the degradation of phenol after 48 hours of incubation by free cells was inhibited by KCN at 47.48%. However, the degradation of phenol after 18 hours incubation by immobilized cells was inhibited by KCN at 52.68%. The lowest concentration of KCN that showed inhibition to phenol degradation was 0.8 ppm. Prolonging the incubation time from 18 hours to 20 hours for KCN has alleviated the inhibition. Other respiratory inhibitors such as carbofuran, paraquat dichloride, atrazine, NaN3 and rotenone showed no effect on phenol-degrading activities and bacterial growth by both free and immobilised cells compared to control (p>0.05). � 2015, Journal of Pure and Applied Microbiology. All rights reserved.

The characterization of bacterial enzymatic pathways of phenol metabolism is important to better understand phenol biodegradation. Phenol hydroxylase is the first enzyme involved in the oxidative metabolism of phenol, followed by further degradation via either meta- or ortho-pathways. In this study, the first known instance of phenol degradation via the meta-pathway by a member of the genus Acinetobacter (Acinetobacter sp. strain AQ5NOL 1) is reported. Phenol hydroxylase converts phenol to catechol, which is then converted via the meta-pathway to 2-hydroxymuconic semialdehyde by the catechol 2,3-dioxygenase enzyme. Phenol hydroxylase extracted from strain AQ5NOL 1 was fully purified using DEAE-Sepharose�, DEAE-Sephadex�, Q-Sepharose� and Zorbax� Bioseries GF-250 gel filtration and was demonstrated by SDS-PAGE to have a molecular weight of 50�kDa. The phenol hydroxylase was purified to about 210.51 fold. The optimum pH and temperature for enzyme activities are 20��C and 7�7.5, respectively. The apparent Km and Vmax values of phenol hydroxylase with phenol as the substrate were 13.4��M and 2.5��mol�min?1�mg?1, respectively. The enzyme was stable at ?20��C for 36�days. � 2016, Accademia Nazionale dei Lincei.

The purpose of this study was to investigate the ability of Acinetobacter sp. strain AQ5NOL 1 immobilised in gellan gum beads to degrade phenol in the presence of heavy metals. Seven different heavy metals, namely, As5+, Cu2+, Cd2+, Ni2+, Cr6+, Pb2+, and Hg2+ at 1 ppm were tested. Results of the study showed that degradation of phenol by free cells was inhibited by Hg2+, Cu2+ and Cr6+ after 48 hours of incubation by 97.91 %, 77.58 % and 75.26 %, respectively. Only Hg2+ and Cr6+ inhibited phenol degradation by immobilised Acinetobacter cells in 18 hours by 67.55 % and 53.19 %. Phenol degradation by immobilised cells was affected when Cr6+ and Hg2+ concentrations exceeded 0.5 and 0.1 ppm, respectively. However, inhibitory effects of heavy metals can be overcome by prolonging the incubation time for immobilised Acinetobacter sp. strain AQ5NOL 1 from 18 hours to 24 and 30 hours for Cr6+ (46.80%) and Hg2+ (21.40%), respectively. � 2017, National Science Foundation. All rights reserved.