Applied Microbiology and Biotechnology, Vol.104, No.21, 9229-9238, 2020
A novel thermostable serine protease from a metagenomic library derived from marine sediments in the East China Sea
Thermal activity and stability are important characteristics for proteases applied in the detergent, pharmaceutical, food, and other green industries. With the intent to discover thermostable novel proteases, we constructed a fosmid metagenomic library from marine sediments in the East China Sea and isolated a clone endowed with high proteolytic activity from this library. Sequence analysis of the positive subclones allowed the identification of a coding region of 1254 bp related to protease activity. The unrooted phylogenetic tree and alignment results revealed that the sequence might be derived fromAnaerolineaceae bacteriumand encodes a new member of the peptidase S8A subfamily with the typical catalytic triad Asp(119)/His(150)/Ser(325). The fusion protein, named pF1AL2, was expressed inEscherichia coliand showed a molecular weight of 35 kDa. pF1AL2 was active in the pH range of 5.0-11.0 with an optimal pH at 10.0 and had high stability under alkaline conditions, retaining more than 95% of its activity after 24 h at pH 11.0. The optimal temperature of pF1AL2 was 80 degrees C, and it retained nearly 80% of its activity after 6 h at 70 degrees C, showing great thermal activity and stability. In addition, the enzyme had great salt tolerance (the residual activity when kept in 3 M NaCl was 40%). Its thermal activity and stability, along with its halotolerance and pH-tolerance, indicate the high potential value of pF1AL2 in industrial applications. The exploitation of pF1AL2 could lay the foundation for the development and utilization of proteases with special features from marine resources by a metagenomic strategy.