CHITINOLYTIC ACTIVITY AT LOW-TEMPERATURE OF AN ANTARCTIC STRAIN (A3) OF VERTICILLIUM-LECANII

The chitinolytic activity of Verticillium cfr. lecanii A3, a strain is olated from continental Antarctica, was compared to those of two selec ted strains of Trichoderma harzianum. After 72 h of incubation at 25 d egrees C in media containing chitin as the sole carbon source, all str ains showed the same enzyme activity (ca. 230 mU/ml); at 15 degrees C, the levels of enzyme activity of the three strains were similar to th ose obtained at 25 degrees C. At 5 degrees C, in contrast, the activit y of V. lecanii was ca. 4 times higher than those of both strains of T . harzianum (203 and 57 mU/ml, respectively; incubation time 144 h). T he chitinase of V. lecanii, purified by preparative isoelectric focusi ng and ion-exchange chromatography, was shown to be a glycoprotein wit h apparent molecular weight of 45 kDa and isoelectric point of 4.9. Th e enzyme was active over a broad range of temperatures (5-60 degrees C ): at 5 degrees C, its relative activity was still 50% of that recorde d at 40 degrees C (optimal temperature). V. lecanii and its purified c hitinase showed clear inhibitory effects on-the growth of some test mo ulds such as Mucor plumbeus, Cladosporium cladosporioides, Aspergillus versicolor and Penicillium verrucosum: observations under the light a nd scanning electron microscopes revealed that growth inhibition was a ccompanied by mycelial damage and cell lysis.