A novel Formosan fungal laccase and its applications
This study identified a new Formosan white-rot fungal strain, Lentinus sp., that can produce extracellular forms of laccases with an activity of approximately 58,300 U/l in culture medium. A purified laccase (designated lcc3) was identified by LC-ESI MS/MS as an N-linkage glycosylated protein. The isolated lcc3 cDNA is composed of 1563 bp encoding for a polypeptide of 521 amino acid residues with 4 putative Cu binding regions. Kinetic analyses revealed that the specific activity, kcat, Km, and kcat/Km of lcc3 at pH 2.5 and 70C with 2,2’-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) used as a substrate was 2,047 U mg-1, 2,017 s-1, 8.4 μM, and 240 s-1μM-1, respectively, which are novel compared to the currently published laccases. Lcc3 is stable at pH 6.0-10.0 and has a midpoint temperature (Tm) of 77.1C, at 25 C, the Tm reached 118 hours. Furthermore, we observed 97% decolorization efficiency on Acid Blue 80, 88% on RBBR, and 61% on Acid Red 37 by lcc3. Structural modeling analysis showed that five, four and three hydrogen bonds can be formed between Acid Blue 80 and Arg178, Arg182, or Asn358; between RBBR and His132, Ser134, or Asp482; and between Acid Red 37 and Arg178, respectively. Notably, Lentinus lcc3 efficiently reversed the toxicity of anthraquinone and azo dyes on rice seed germination, decolorized industrial textile effluent, and partially removed residue lignin in kraft pulp, suggesting the enzyme may be valuable for bioremediation and textile industry. The results obtained from this study are not only published on top ranking journal (Environmental Science and Technology), 3.9% (8/205) in the Environmental Science research field, but also is applying for US patent (pending).Co-researchers:Chih-An Hsu, Tuan-Nan Wen, Yu-Chang Su, Zhi-Bing Jiang, Chin-Wen Chen, and Lie-Fen Shyur*