Exploration of phenol tolerance mechanism through antioxidative responses of an evolved strain, Chlorella sp. L5

Abstract

Phenol is a typical pollutant which can be degraded by microalgae. Phenol induces formation of reactive oxygen species (ROS). Tolerance to oxidative damage produced by ROS is critical for phenol degradation by microalgae. An evolved strain, Chlorella sp. L5 was obtained from Chlorella sp. L3 in a previous study. The current study investigated the phenol tolerance mechanism by the dynamic responses of antioxidative enzyme activities of Chlorella sp. L3 and Chlorella sp. L5 in TAP medium with and without 500 mg L−1 phenol. It was shown that the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were increased in Chlorella sp. L5 when phenol was added in the medium. They were also significantly higher than those of Chlorella sp. L3 under 500 mg L−1 phenol conditions. There were slight increases of the malondialdehyde (MDA) contents of Chlorella sp. L5 in TAP medium with and without 500 mg L−1 phenol while they were significantly lower than the MDA content of Chlorella sp. L3 under 500 mg L−1 phenol conditions. The results indicated that Chlorella sp. L5 had higher tolerance to 500 mg L−1 phenol than Chlorella sp. L3. The antioxidative responses of Chlorella sp. L3 and Chlorella sp. L5 in control and TAP medium + phenol were consisted with the results of the comparative transcriptomic analysis in another published result. The phenol tolerance mechanism was also confirmed by the photosynthetic efficiency under oxidative conditions and control.