AEROBIC TRANSFORMATION OF SHORT-CHAIN ALKYLPHENOL POLYETHOXYLATES BY MIXED BACTERIAL CULTURES

Various aerobic mixed bacterial cultures, isolated from wastewater, ri ver water, and from a forest soil, were applied for the biotransformat ion of short-chain alkylphenol polyethoxylates (APnEO; nEO = 1-3) usin g the shake culture technique. Almost complete transformation of both nonylphenol- and octylphenol polyethoxylate mixtures, added to a synth etic sewage at total concentrations in the range of 0.5-2.5 mg/L, was achieved within 6-23 days. The duration of the adaptation period (lag phase) and the transformation rate in exponential phase varied signifi cantly, depending on the origin of the bacterial culture and structura l characteristics of the APnEO molecules (number of EO groups per mole cule and the size of the alkyl chain). Experiments conducted in a mine ral medium showed that short-chain APnEO can be transformed even if th ey represented the only source of organic carbon, though at a rate sig nificantly lower than that in the synthetic sewage. Autochthonous bact erial cultures originating from a polluted river and a secondary sewag e effluent were also able to transform short-chain APnEO, the transfor mation rate being strongly dependent on temperature. The analyses of s hake culture at the end of the exponential phase revealed a significan t presence of alkylphenoxy carboxylic acids which accounted for up to 90% of APnEO originally added to the growth-media. This suggested that carboxylation of the terminal alcohol group was the most important tr ansformation process involved.