Biodegradation of phthalic acid esters by immobilized microbial cells

Microorganisms capable of degrading di-n-butyl phthalate (DBP) were immobilized by polyvinyl alcohol (PVA) and used for DBP degradation. The characteristics of DBP degradation by immobilized and free cells were investigated. The experimental results showed that the degradation rate of immobilized cells was higher than that of free cells. The optimal pH and temperature for DBP degradation were determined to be 7.0 and 25°C, respectively. The semi-continuous degradation test demonstrated that high-frequency feeding of low concentration (50 mg/L) was more favourable than low-frequency feeding of high concentration (150 mg/L) for DBP degradation. The main intermediates of DBP degradation by immobilized cells were identified using a gas chromatography/mass spectrometry method. The results revealed the presence of monobutyl phthalate, phthalic acid, and protocatechuate. A tentative pathway for DBP degradation was proposed, which demonstrated that the metabolic mechanism of immobilized cells remained the same as that of the free cells.