Ten species of white-rot fungi were evaluated for their ability to decolorization of palm oil mill effluent. The highest decolorization efficiency was found with Trametes elegans (PP17-06), followed by Ganoderma sp.2 (PW17-06) and Ganoderma sp.2 (PW17-177), respectively. T. elegans was further evaluated for the long-term performance of decolorization for 24 d. The optimal retention time for the decolorization was 8 d, with a color removal efficiency of 47.7%. Beyond 18 d of incubation, decolorization efficiency was reduced due to the autolysis of enzymes. During the biodegradation process, manganese peroxidase enzyme activities reached a maximum of 36.03 U.L−1. However, no significant laccase and lignin peroxidase activities were observed. T. elegans was also assessed for decolorization performance through biosorption on mycelial biomass. The synthesis of the enzyme was prevented by exposing the mycelium to HgCl2. Within an optimal contact time of 2 d, decolorization efficiency reached 12.5% with ADMI reduction from 4259.0 (±20.1) ADMI to 3727 (±104.04) ADMI. Results indicate that the adsorption capacity was reached at this time, and no significant color removal can be achieved by biomass. Results obtained in this study showed the potential of T. elegans in decolorizing palm oil mill effluent.

Contamination of water with Malachite green (MG) may threaten aquatic and human life. Nitrogen-fixing Azotobacter sp. is an efficient adsorbent for the removal of MG from dye solutions. The optimum pH for the biosorption process was determined. The maximum adsorption capacity and the effect of different adsorbate concentrations were detected. The kinetics and isotherm models for biosorption were constructed. Optimum adsorption of MG by Azotobacter sp. was obtained at pH 6.0, biomass concentration was 0.05%, initial dye concentration was 50 mg.L-1, and contact time was 600 mins. Dye adsorption exhibited an increase with contact time and initial malachite green concentration. The kinetics of the adsorption process was best followed by the pseudo-second-order kinetic model which confirms the chemisorption process. The adsorption equilibrium data fit well to the Langmuir model indicating a monolayer adsorption behavior onto a surface of Azotobacter sp. with a finite number of active sites. Maximum biosorption capacity was found to be 142.8 mg.g-1 of bacterial biomass. The dry biomass of Azotobacter sp. has proved to be an efficient biosorbent for the removal of synthetic dyes from actual industrial effluent that is contaminated with up to 400 mg.L-1 dye concentration.