Enhanced Decolourization of Congo Red Dye by Malaysian Rhodococcus UCC 0010 Immobilized in Calcium Alginate

Abstract

The world’s once glorious environment is heavily impacted by pollution caused by many industrial activities. The textile industry in particular has its share in pollution of water, land and air. With limited water resources and fast emerging nature of the textile industry in our nation, this raises concern in regards to detrimental effect of improper textile industry waste management. This waste is toxic and noxious which negatively affect living organisms and the environment when discharged without proper treatment. Utilization of microorganism through green chemistry approach is an alternative for industrial application to be sustainable, eco-friendly, cost- and time-effective compared to conventional effluent treatment methods that have considerable drawbacks. This study is interested in subjecting Rhodococcus sp. that is sturdy and resilient to decolourize di-azo dye Congo red, a highly recalcitrant and toxic dye since no previous studies have been reported with similar objective. Screening studies showed 8 strains were capable of forming halo zone around colony on 0.1 g/L Congo red agar plate with UCC 0010 giving largest halo zone with 1 cm diameter at day 5 of incubation. Similar results were obtained for Congo red decolourization in 24 hours at static condition for resting cells and heat-killed cells with 46d ± 1.5 % and 46d ± 7 % dye removal respectively. This shows dye removal is majorly via biosorption since cells were deeply coloured. Live cells yielded higher decolourization compared to resting cells with 67c ± 1.7% decolourization, possibly due to active metabolic state. Cells immobilized in both calcium alginate and gellan gum showed significantly higher decolourization and biosorption to matrix in control set. However calcium alginate is selected as best entrapment matrix since drastic difference was seen between control set and dye solution inoculated with biobeads (beads containing UCC 0010) indicating enzymatic action for Congo red decolourization.