Aims:  This research aims to investigate the efficiency of two lipolytic enzymes – fungal cutinase and yeast esterase – upon the biodegradation of dihexyl phthalate (DHP). Method and Results:  During the enzymatic degradation of DHP dissolved in methanol, several degradation products were detected and their time‐course changes were monitored using GC/MS. The DHP‐degradation rate of cutinase was surprisingly high; i.e. almost 70% of the initial DHP (500 mg l−1) was decomposed within 4·5 h. Although the same amount of esterase was employed, more than 85% of the DHP remained after 3 days. Almost all the DHP was converted by cutinase into 1,3‐isobenzofurandione (IBF), whereas hexyl methyl phthalate and IBF were abundantly produced by esterase. In addition, the toxicities of the DHP‐degraded products by esterase were evaluated using various recombinant bioluminescent bacteria, which caused oxidative and protein damage, whereas the hydrolysis products from cutinase never caused any cellular damage in the methanol‐containing reaction system. Conclusions:  Cutinase starts to act as a DHP‐degrader much earlier and faster than esterase, with high stability in ester‐hydrolytic activity, therefore a plausible approach to the practical application of cutinase for DHP degradation in the DHP‐contaminated environments may be possible. Significance and Impact of the Study:  This study describes the enhanced degradation and detoxification of DHP using Fusarium oxysporum f. sp. pisi cutinase.

The efficiency of two lypolytic enzymes (fungal cutinase, yeast esterase) in the degradation of dipropyl phthalate (DPrP) was investigated. The DPrP-degradation rate of fungal cutinase was surprisingly high, i.e., almost 70% of the initial DPrP (500 mg/l) was decomposed within 2.5 h and nearly 50% of the degraded DPrP disappeared within the initial 15 min. With the yeast esterase, despite the same concentration, more than 90% of the DPrP remained even after 3 days of treatment. During the enzymatic degradation of DPrP, several DPrP-derived compounds were detected and time-course changes in composition were also monitored. The final chemical composition after 3 days was significantly dependent on the enzyme used. During degradation with fungal cutinase, most DPrP was converted into 1,3-isobenzofurandione (IBF) by diester hydrolysis. However, in the degradation by yeast esterase, propyl methyl phthalate (PrMP) was produced in abundance in addition to IBF. The toxic effects of the final degradation products were investigated using various recombinant bioluminescent bacteria. As a result, the degradation products (including PrMP) from yeast esterase severely caused oxidative stress and damage to protein synthesis in bacterial cells, while in the fungal cutinase processes, DPrP was significantly degraded to non-toxic IBF after the extended period (3 days).