Pentachlorophenol degradation by Janibacter sp., a new actinobacterium isolated from saline sediment of arid land

Abstract

Many pentachlorophenol- (PCP-) contaminated environments are characterized by low or elevated temperatures, acidic or alkaline pH, and high salt concentrations. PCP-degrading microorganisms, adapted to grow and prosper in these environments, play an important role in the biological treatment of polluted extreme habitats. A PCP-degrading bacterium was isolated and characterized from arid and saline soil in southern Tunisia and was enriched in mineral salts medium supplemented with PCP as source of carbon and energy. Based on 16S rRNA coding gene sequence analysis, the strain FAS23 was identified as Janibacter sp. As revealed by high performance liquid chromatography (HPLC) analysis, FAS23 strain was found to be efficient for PCP removal in the presence of 1% of glucose. The conditions of growth and PCP removal by FAS23 strain were found to be optimal in neutral pH and at a temperature of 30 °C. Moreover, this strain was found to be halotolerant at a range of 1-10% of NaCl and able to degrade PCP at a concentration up to 300 mg/L, while the addition of nonionic surfactant (Tween 80) enhanced the PCP removal capacity.

Figure 1

The phylogenetic position of Janibacter sp. strain in relation to some members of actinobacteria (genus of Janibacter, Sphingomonas, Terrabacter, Terracoccus, Kocuria, and Arthrobacter) based on 16S rRNA gene. Bootstrap values for a total of 1000 replicates are shown at the nodes of the tree. The scale bar corresponds to 0.05 units of the number of base substitutions per site changes per nucleotide.

Figure 2

The growth (a) and the PCP removal (b) in the presence and in deficiency of the supplementary carbon source (glucose: 1%) by Janibacter sp. FAS23. Error bars represent the standard deviation.

Figure 3

(a) Growth of Janibacter sp. at different pH of culture medium: pH 4.0, pH 6.9, and pH 9.0 with 20 mg/L of PCP at 30°C. (b) Effect of different pH on the PCP removal efficiency by Janibacter sp. Error bars represent the standard deviation.

Figure 4

(a) Growth of Janibacter sp. at different temperatures in presence of 20 mg/L of PCP and at pH 6.9. (b) Effect of temperature changes on the PCP removal efficiency by Janibacter sp. Error bars represent the standard deviation.

Figure 5

(a) Growth of Janibacter sp. in the presence of 0, 20, 50, 100, 200, and 300 mg/L of PCP. (b) Effect of different PCP concentrations on the PCP removal by Janibacter sp. Error bars represent the standard deviation.

Figure 6

(a) Growth of Janibacter sp. in MS medium supplemented with different concentrations of NaCl: 0%, 1%, 3%, 6%, and 10% in the presence of 20 mg/L of PCP at 30°C. (b) Effect of NaCl on the PCP removal efficiency by Janibacter sp. Error bars represent the standard deviation.

Figure 7

(a) Growth of Janibacter sp. in MS medium supplemented with nonionic surfactant Tween 80 (40 mg/L) containing 20 and 300 mg/L of PCP. (b) Effect of nonionic surfactant Tween 80 on the PCP removal efficiency by Janibacter sp. Error bars represent the standard deviation.