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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Benzophenone proved to be readily biodegradable according to OECD criteria. The enrichment culture of the microbial strain MU-1 (black yeast Rhinocladiella aquaspersa) isolated from activated sludge was able to degrade benzophenone: Low benzophenone concentrations were degrade by more than 95% within several days (degradation: 100 mg/L within 3 d; 1000 mg/L within 7 d). Based on GC/MS analysis, benzophenone was degraded into hydrophilic compounds with very low molecular mass via conversion to phenol. Low concentrations of benzophenone can be biodegraded by microbes occurring in natural water samples. The rates of microbial degradation, however, were different due to the different composition and amounts of microbes (East Lake water: ca. 50% degradation after 12 d; Changjiang River water: ca. 25% degradation after 12 d). 

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

In a study conducted according to OECD Guideline 301F (Ready Biodegradability: Manometric Respirometry Test), biodegradation started on day 10 in one flask, on day 20 in the other, and resulted in 66 -84% mineralization of the test substance after 28 days of incubation. According to OECD criteria, benzophenone proved to be readily biodegradable in this study.

Environmental samples (activated sludge, soil samples) were tested for the occurrence of benzophenone-degrading activity. Benzophenone degradation in the cultures was monitored via GC/MS. Cultures showing benzophenone-degrading activity were subcultured five times and isolated after enrichment on YPD agar at 25°C for 3 d. Significant benzophenone-degrading activity was observed in the culture of one activated sludge sample. It was found that the degrading activity was increased through subculturing indicating the enrichment of benzophenone-degrading microbes in the culture. The microbial strain isolated from the culture was designated as the strain MU-1. Based on the phylogenetic analysis, MU-1 can be assumed to be the black yeast Rhinocladiella aquaspersa. MU-1 degraded more than 95% of benzophenone (100 -1000 mg/L) as a sole carbon source within several days; ca. 20% of benzophenone were degraded within 40 d at a concentration of 5000 mg/L (no degradation observed at 10000 mg/L after 40 d). Based on GC/MS analysis, benzophenone was degraded into hydrophilic compounds with very low molecular mass via conversion to phenol.

The microbial degradation of benzophenone (10 µg/L) in the aquatic environment was investigated using natural water from the non-polluted Changjiang River and East Lake (Wuhan, China), respectively. A stock solution of benzophenone was added to natural lake and river water. The solutions were stored in cool, dark and anaerobic conditions for 12 d. Biodegradation was monitored by HPLC/UV analysis. The degradation of benzophenone was faster in East Lake water (ca. 50% after 12 d) than in Changjiang River water (ca. 25% after 12 d). The results indicate that benzophenone was biodegradated by microbes in real water samples. The rates of microbial degradation, however, were different due to the different composition and amounts of microbes. In the controls (pure water/Lake water/River water + sodium azide) only very weak degradation was observed.