Triphenylmethanes, malachite green and crystal violet dyes decolourisation bySphingomonas paucimobilis

In this study, Gram negative bacterium,Sphingomonas paucimobilis, was used to test its ability to decolourise two triphenylmethane dyes: malachite green (MG) and crystal violet (CV) in mineral salts medium (MSM). Decolourisation was examined with dye concentrations (2.5, 5, 15, 25, 30 and 50 mg/l), glucose (0, 1.4, 2.8, 4.2, 5.6 and 7 mM) and yeast extract concentrations (0, 0.05, 0.10, 0.15% w/v). Our results showed thatSphingomonas paucimobilis used at 1 OD (λ 600 nm), equivalent to 14×107 CFU/ml cell concentration, remove MG and CV colour with 35 and 55%, respectively, for 2.5 mg/l dye concentration in MSM. The best removal efficiencies for decolourisation were 93.43% for MG and 71.29% for CV at 50 mg/l dye concentration, obtained with 7 mM of glucose used as source of carbon. Whereas the optimum concentration of yeast extract which allowed high value on decolourisation was determined at 0.1% for MG and 0.05% for CV. We obtained the high percentage of decolourisation which reaches 100% within 10 h. Moreover, at the same conditions the source of nitrogen yeast extract enhanced more rapidly the decolourisation of dyes colour removal by a new natural isolatesSphingomonas paucimobilis which was significantly affected by adding nutrient sources.