Phenol degradation by Acinetobacter sp . in the presence of heavy metals

ability of Acinetobacter gellan gum beads to degrade phenol in the presence of heavy metals. Seven different heavy metals, namely, As, Cu, Cd, Ni, Cr, Pb, and Hg inhibited by Hg, Cu and Cr after 48 hours of incubation by 97.91 %, 77.58 % and 75.26 %, respectively. Only Hg and Cr inhibited phenol degradation by immobilised Acinetobacter cells in 18 hours by 67.55 % and 53.19 %. Phenol 6+ and Hg concentrations exceeded 0.5 and 0.1 ppm, respectively. prolonging the incubation time for immobilised Acinetobacter Cr (46.80 %) and Hg (21.40 %), respectively.


INTRODUCTION
Heavy metals can be toxic to microorganisms even at colonise noxious metal-polluted environments (Yusuf et al., 2016).Certain bacteria have developed capabilities to protect themselves from heavy metal toxicity by various mechanisms (Shukor et al., 2010;Halmi et al et al., 2015).Bioremediation is effective in degrading pollutants and thus able to get rid phenolic compounds, dye, crude oil and hydrocarbons (Suhaila et al., 2013;Ahmad et al., 2014;Chander et al., et al., 2015).
ability to degrade 100 % phenol up to 1100 mg/L and 1900 mg/L by free and immobilised cells, respectively in 10 days.As both heavy metals and phenol are harmful out to determine the effects of selected heavy metals on phenol degradation by the bacterium Acinetobacter sp.. effective bioremediation strategies.

Microorganism and culture condition
The phenol-degrading Acinetobacter sp.strain by

Immobilised cells
by Ahmad et al. (2012).A combination of 7.5 % of as the entrapment matrix.In this study, degradation of 0.5 g/L phenol by free and immobilised cells (3.5 g/L of assay for phenol using 4-aminoantipyrene as the reagent (APHA, 1998).

The effects of heavy metals
The effect of heavy metals on phenol degradation by the bacterium Acinetobacter determined using both free and immobilised cells.In (As 5+ ), chromium (Cr 2+ ), cadmium (Cd 2+ ), cuprum (Cu 2+ ), nickel (Ni 2+ ), lead (Pb 2+ ), and mercury (Hg 2+ )] each at 1 ppm concentration.Bacterial cultures in free rotary shaker at room temperature at 150 rpm.Based on this study (Figure 1), degradation of 0.5 g/L phenol cells and 48 hrs for free cells, because these are the optimal incubation periods for 100 % removal of phenol.forming units methods, respectively.

Statistical analysis
of the experiment and expressed as mean ± standard deviation (STDEV).

RESULTS AND DISCUSSION
Cell immobilisation is a promising approach in phenol biodegradation compared to free cells.In this study, immobilised Acinetobacter than free cells at 0.5 g/L of phenol (Figure 1 Hg 2+ is considered the most toxic non-radioactive metal in the environment and is toxic in any form  pig farms (DOE, 2002).This heavy metal also appears in phenol-polluted environments.Hence, the effect of Hg 2+ the presence of 1 ppm Hg 2+ 100 % of bacterial than 70 % of phenol-degrading activities by immobilised cells.Hg 2+ concentrations ranging from 0.1 to 1.0 ppm 0.5 ppm, the metal inhibited more than 60 % of phenoldetrimental (Ahmad et al., 2015).But, the inhibitory effect can be overcome by prolonging the incubation time for immobilised Acinetobacter from 18 to 28 hours (Figure 3).The inhibition of phenol degrading activities by 0.1 to 0.4 ppm of Hg 2+ at 21 hours, 0.6 to 0.8 ppm at 22 hours, 0.9 ppm at 24 hours, and 1.0 ppm at 28 hours (Figure 3b).In previous studies, Hg 2+  of phenolic compounds by inhibiting hydroxylases

Table 1 :
Nair et al., 2008; Arif et al et al., 2015).Heavy metals directly affect the membrane structure by disturbing the electron transport chain (Hall, 2002; Russak et al., 2008).Freely-suspended cells are exposed directly to the heavy degradation by disturbing the membrane structure.The effect of different heavy metals (1 ppm) on phenol biodegradation by freely-suspended and immobilised Acinetobacter The results revealed that Cr 6+ , Cd 2+ , and Hg 2+ inhibited at 5.5, 5.3 and 0.0 Log 10 (CFU), respectively compared to the control 8.2 Log 10 adapt and protect itself from Cu 2+ , As 5+ , Ni 2+ , and Pb 2+ et al., 2015).Hg 2+ gave the highest degraded, respectively after 18 hours.Immobilised cells suspended cells after 18 hours.The immobilised cells heavy metals, thus reducing the chance of heavy metals interrupting the degradation process (Chung et al., 2003).The application of immobilised cells in bioremediation exhibits many advantages over free cells, including the stability of active cells, recovery of cells, and reusability of the immobilised system (Yun et al., 2009; Ahmad et al., Comparison of the kinetic parameters of phenol degradation by free and immobilised Acinetobacter 1 ppm.Values are mean ± standard deviation (n = 3)Ibrahim et al., 2016).In addition, cells on the outer layer exposed to heavy metals adsorb the heavy metals, and become a protective layer to cells immobilised deep in the matrix(Ahmad et al., 2012).A summary of the

Table 2 :
The effect of different concentrations of chromium and mercury on phenol biodegradation by immobilised Acinetobacter deviation (n = 3) ppm As, Cu, Cd, Ni, Cr, Pb and of phenol by this bacterium.The inhibitory effects of chromium and mercury on immobilised cells could be overcome by prolonging the incubation period.The range of concentrations of heavy metals utilised in this study is very similar to the concentration range of heavy metals detected in the environment according to several studies and reports(Shukor et al., 2008; DOE, 2010).The results indicate that the immobilised bacterium heavy metals.