Comparison of the functional characterization between alkane monooxygenases for low-molecular-weight polyethylene biodegradation

Abstract

AlkB1 of the Pseudomonas aeruginosa strain E7 is known as an enzyme that is used in alkane degradation. It has been reported that AlkB1 is active for degradation of low molecular weight polyethylene (LMWPE-1) and that degradation increased in the presence of RubA1, RubA2, and RubB. As an extension of these results, this study investigated the activity of AlkB2 toward LMWPE-1 degradation and the mutual interaction between AlkB2 and RubA1/RubA2. The activity of AlkB1 in LMWPE-1 degradation was compared with that of AlkB2. An examination of the transcription levels of alkB1 and alkB2 induced by n-dodecane and n-hexadecane indicated that the transcription of alkB1 was induced by n-hexadecane but not by n-dodecane, whereas that of alkB2 was induced by both n-dodecane and n-hexadecane. The transcription level of alkB2 induced by n-hexadecane was about 7 times higher than that of alkB1. The transcription of alkB2 was also higher and persisted longer than that of alkB1 in the presence of LMWPE-1. The results of LMWPE-1 biodegradation by BCA (inserted alkB1), BCA2 (inserted alkB2), and BCA2R (inserted alkB2, rubA1 and rubA2) recombinant strains under controlled compost conditions revealed that LMWPE-1 biodegradation by the BCA2 strain was higher than that by the BCA strain, and the biodegradation activity of the BCA2 strain was similar to that of the strain cloned with alkB1, rubA1, rubA2, and rubB. LMWPE-1 biodegradation by the BCA2R strain was not higher than that by the BCA2 strain, even though the BCA2R strain contains RubA1 and RubA2. Therefore, it was concluded that AlkB2 is more effective than AlkB1 toward LMWPE-1 degradation, and that the regulation mechanism of AlkB2 is different from that of AlkB1.