Toxic effects of linear alkylbenzene sulfonate, anthracene and their mixture on growth of a microbial consortium isolated from polluted sediment

The aim of this study was to determine the effect of linear alkylbenzene sulfonate (LAS), anthracene and a LAS-anthracene mixture on the growth of a microbial consortium isolated from polluted sediment. The microbial consortium was grown in a sterile glass bottle with mineral medium containing 1 g/L of glucose. Microbial growth inhibition produced by LAS, anthracene and combinations of LAS and anthracene was determined by viable count in nutritive agar; inhibitory concentration 50 (IC50) was calculated. The concentrations evaluated were 0.16, 0.8, 1.6, 16 and 160 mg/L of LAS or anthracene. The LAS-anthracene mixtures were prepared by fixing either LAS or anthracene at 0.16 mg/L while increasing the other compound at the above concentrations. Microbial growth was sensitive to LAS at an IC₅₀ of 8.22 and to anthracene at an IC₅₀ of 5.2 mg/L. In the LAS-anthracene combination, if LAS concentration was fixed and anthracene concentration varied, IC₅₀ (5.92 mg/L) was similar to IC₅₀ for anthracene alone. In contrast, the inhibition effect was diminished when anthracene remained constant and LAS concentration was increased (IC₅₀: 70.11 mg/L). The sediment microbial populations were capable of degrading the LAS-anthracene mixture if the concentration of both compounds were at 0.16 mg/L.