Production of two novel laccase isoforms by a thermotolerant strain of Pycnoporus sanguineus isolated from an oil-polluted tropical habitat

Resumen

A thermotolerant and halotolerant strain of Pycnoporus sanguineus was isolated from an oil-polluted site in a tropical area located in Veracruz, Mexico. This strain was able to grow at 47ºC and in culture medium containing 500 mM NaCl. The strain was also tolerant to the presence of 30,000 ppm of crude Maya oil. A 68-kDa protein purified submerged cultures exhibited laccase activity towards 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), guaiacol, syringaldazine and o-dianisidine, for which it presented the highest affinity (Km = 43 µM). Two-dimensional gel electrophoresis analysis showed that, unusual for laccases, the enzyme has two active isoforms, with isoelectric points of 7.00 and 7.08. The purified enzyme showed high thermostability, retaining 40% of its original activity after 3 h at 60ºC. This property seems to correlate with a long “shelf-life”, given that at 40ºC enzyme activity was only gradually lost over a 5-day period incubation. Both, the fungus and its laccase aer likely to have high potential for biotechnological applications.