Chlorophenolic waste most often contains phenol and rho-cresol along with chlorophenols. A Rhodococcus erythropolis strain M1 was isolated with the ability to degrade 2-chlorophenol, phenol and p-cresol (100 mgl(-1), each) in 18, 24 and 20 h, respectively, with negligible lag. However, Rhodococcus sp. characterized by low growth rate, pose a threat to be outgrown by bacteria occurring in natural habitats. In the present study, interaction of R. erythropolis M1 with another isolated bacteria generally encountered in activated sludge for water treatment like Pseudomonas fluorescens P1 was studied. 2-chlorophenol, phenol and p-cresol were selected as the substrates for the study. Viable cell counts showed competitive interaction between the species on 2-chlorophenol and phenol. Specific growth rate of pure culture of R. erythropolis M1 was higher than P. fluorescens P1 on 2-chlorophenol. However, in mixed culture, P. fluorescens P1 showed higher growth rate. Degradation of phenol showed higher growth rate of R. erythropolis M1 both in pure and in mixed culture form. Degradation of p-cresol had shown similar counts for both populations indicating neutral type of interaction. This observation was substantiated by detecting the growth rate, where both cultures had similar growth rate in pure and in the mixed culture form. Rate of 2-chlorophenol degradation was higher when R. erythropolis M1 was used as the pure culture as compared to the degradation rates observed with the P. fluorescens P1 or with the mixed culture. However, in case of phenol and p-cresol, degradation by the mixed culture had resulted in higher degradation rates as compared to the degradation of the substrates by both the axenic cultures.
A Pseudomonas sp. (S1), isolated from soil by an enrichment technique was tested for its potential to degrade different cyanide compounds. Further, biodegradation/biotransformation of binary mixtures of the cyanide compounds by the culture was also studied. The results indicated that the culture could grow on the following nitriles by using them as carbon and nitrogen sources: acetonitrile, butyronitrile, acrylonitrile, adiponitrile, benzonitrile, glutaronitrile, phenylacetonitrile, and succinonitrile. Studies on the biodegradation of these cyanide compounds in binary mixtures showed that the presence of acrylonitrile or KCN delayed the degradation of acetonitrile in a mixture, while none of the other cyanide compounds affected the degradation of one another. The transformation products of the nitriles were their corresponding acids, and similarly, KCN was also directly transformed to formic acid. Studies on the transformation of these cyanide compounds showed that the rate of transformation of nitriles to their corresponding carboxylic acids was acrylonitrile > acetonitrile > adiponitrile > benzonitrile > KCN. This culture has the unique characteristic of transforming representatives of saturated aliphatic, aliphatic olefinic, aromatic, and aralkyl nitriles, as well as alkali cyanide, to their corresponding carboxylic acids.
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