Naphthalene degradation studies using Pseudomonas sp. strain SA3 from Alang-Sosiya ship breaking yard, Gujarat

Abstract

Polycyclic aromatic hydrocarbons (PAHs) remediation has received considerable attention due to their significant health concern and environmental pollution. However, PAHs contaminated sites also contain indigenous microbes that can potentially degrade naphthalene. Therefore, this study aimed to isolate, characterise and optimise process parameters for efficient naphthalene degradation. A total of 50 naphthalene degrading bacteria were isolated from Alang-Sosiya ship breaking yard, Bhavnagar, Gujarat and screened for their naphthalene degrading capacity. The selected isolate, Pseudomonas sp. strain SA3 was found to degrade 98.74 ± 0.00% naphthalene at a concentration of 500 ppm after 96 h. Further, optimisation of environmental parameters using one factor at a time approach using different inoculum sizes (v/v), pH, salinity, temperature, carbon and nitrogen source greatly accelerated the degradation process attaining 98.6 ± 0.46% naphthalene degradation after 72 h. The optimised parameters for maximum naphthalene degradation were pH 8, 0.1% peptone as nitrogen source, 8% salinity and 1% (v/v) inoculum size.

Keywords: Alang-Sosiya ship breaking yard; Biodegradation; Naphthalene; Polycyclic aromatic hydrocarbons (PAHs); Pseudomonas sp..

Figure 1

Sampling site and physicochemical parameters of soil and water.

Figure 2

Phylogenetic tree of potential isolates SA3 and SB5. This analysis involved 7 nucleotide sequences. All positions containing gaps and missing data were eliminated (complete deletion option). There were a total of 1281 positions in the final dataset. Evolutionary analyses were conducted in MEGA X (Kumar et al., 2018).

Figure 3

Biodegradation of naphthalene by Pseudomonas sp. strain SA3 and Pseudomonas taiwanensis strain SB5. The values are presented as mean values ±SD, n = 3.Values followed by different alphabets within the treatment are significantly different at p < 0.05 using Fisher's LSD. (n.d: not detectable).

Figure 4

Naphthalene degradation and growth pattern of Pseudomonas sp. strain SA3.

Figure 5

Effect of environmental parameters on naphthalene degradation. (a) Effect of inoculum size (v/v) on naphthalene degradation. (b) Effect of pH on naphthalene degradation. (c) Effect of salinity on naphthalene degradation. (d) Effect of temperature on naphthalene degradation. (e) Effect of carbon and nitrogen source on naphthalene degradation. The values are presented as mean values ± SD, n = 3.Values followed by different alphabets within the treatment are significantly different at p < 0.05 using Fisher's LSD.