Biodegradation of hydroxylated and methoxylated benzoic, phenylacetic and phenylpropenoic acids present in olive mill wastewaters by two bacterial strains

Two aerobic bacterial strains, a chlorophenol-degrading bacterium character ized in this work as a Ralstonia sp. LD35 on the basis of the sequence of t he gene encoding for 16S ribosomal RNA, and Pseudomonas putida DSM 1868, ca pable of metabolizing 4-methoxybenzoic acid, were tested for their capacity to degrade monocyclic aromatic acids responsible for the toxicity of olive mill wastewaters (OMWs). Both strains possess interesting and complementar y degradation capabilities in resting cell conditions: Ralstonia sp. LD35 w as found to metabolize 4hydroxybenzoic, 4-hydroxyphenylacetic, 3,4-dihydrox ycinnamic and cinnamic acid, whereas DSM 1868 was capable of metabolizing 4 -hydroxy-3-methoxybenzoic. 3,4-dimethoxybenzoic and 3-hydroxy-3,5-dimethoxy benzoic acid, as well as 4-hydroxybenzoic and 4-hydroxyphenylacetic acid. T he kinetic parameters describing the growth of the two strains on the same compounds were determined in growing-cell batch conditions, and showed that both strains presented high affinity and high specific growth rates toward s all assayed substrates. In addition, the two strains were capable of grow ing on and extensively biodegrading a mixture of monocyclic aromatic acids commonly found at high concentrations in OMWs, and of growing on a 20% dilu tion of a natural OMW. All these features make the two strains attractive c andidates for the development of a biotechnological process for the biodegr adation of aromatic compounds found in OMWs. (C) 2001 Editions scientifique s et medicales Elsevier SAS.