Biodecolourisation of textile dyes by local microbial consortia isolated from dye polluted soils in ngaoundere (Cameroon)

Azo dyes are xenobiotic and recalcitrant against biodegradation, causing environmental problems. Under certain environmental conditions, microorganisms can transform dyes to non-coloured products or completely mineralize them. In the present study, the first attempt on dye decolourisation potentials of local microbial consortia isolated from dye contaminated soils in Ngaoundere-Cameroon were determined against two azo dyes. Decolourisation rate and kinetics were monitored by spectrophotometry under different conditions. Effect of process parameters: pH, dye concentration and inoculums size on dye decolourisation rate was optimised using the full factorial design. Microbial growth and decolourisation rate were higher in shaking than static conditions. The bacteria consortium gave highest decolourisation of 91.86% for azo blue and 93.75% for azo orange within 48 hours in shaking cultures; 57.78% and 62.06% respectively after 48 hours under static condition, followed by the mixed and fungi consortium. Kinetics studies revealed the bacteria consortia had highest tendency towards decolourisation, with a greater halflive value for azo blue (13.97 hours) than for azo orange (10 hours). pH out of the range 7.2–8 and dye concentrations above 100mg/1 reduced decolourisation rate by the bacteria consortia while increasing inoculums size increased it. Optimum decolourisation was achieved when pH and dye concentrations were kept low while the inoculums size was high.