Chlorinated biphenyl degradation by wild yeasts pre-cultured in biphasic systems

ABSTRACT

Environmental biotechnology has developed as an offshoot from sanitary engineering, and only recently the biological component of the ecosystems had been recognized as relevant when bioremediation strategies must be chosen to solve environmental problems. Yeasts were isolated on 2,4-dichlorobiphenyl, 2,3',4- and 2,4',5-trichlorobiphenyl, poorly soluble compounds in water, as carbon sources. Debaryomyces castelli, Debaryomyces maramus and Dipodascus aggregatus composed the mixed culture and represented 72 percent of the isolates; their degradation potential were studied in biphasic and monophasic systems. The biphasic cultures were obtained with phenol as the organic phase and MSM as the aqueous ones, the monophasic medium only with MSM. Both cultures were supplied with 50, 100, 150 and 200 ppm DCB, TCB-3' and TCB-4' as substrate. The growth rates varied with the dispersion degree, agitation rates and cell adhesion to the organic phase. The water-phenolic system improved yeasts selection in pollutant presence with low water solubilities, indeed, the adaptation and degradation were more slowly in the monophasic aqueous medium. Bioremediation is based on the presence of efficient microbial populations and pollutant availability; the tested yeasts and the organic-water system assayed put forward the possibility that hydrophobic substrates could be mineralized in natural habitats by wild yeast consortium.