Candida tropicalis can use phenol as the sole carbon and energy source. Experiments regarding phenol degradations from the water phase were carried out. The fermentor was operated as a fed-batch system with oxistat control. Under conditions of nutrient limitation and an excess of oxygen the respiration activity of cells was suppressed and some color metabolites (black-brown) started to be formed. An accumulation of these products inhibited the cell growth under aerobic conditions. Another impact was a decrease of the phenol hydroxylase

Interactions amongst the degradation rates of toluene, xylenes, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and n-butyl acetate (n-BA) were investigated. Experiments were performed in a biotrickling filter reactor packed with polypropylene Pall rings in a counter-current air-water mode of operation. Under pseudo-steady-state conditions, the removal efficiency (RE) of the individual components in the middle of and at the effluent above the reactor bed was evaluated. By using a mixed microbial culture as the biocatalyst, the results revealed that an increased loading of toluene and xylene had a competitive effect on the RE of MIBK. After reaching a saturation point of the overall catabolic capacity of the biocatalyst, variations of RE were observed for the different components. This was most pronounced under conditions of overloading with the water-soluble components mixture. Despite such variations, the system was able to efficiently degrade this complex pollutant mixture for a period of 1 yr.

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