Characterization of an amylase produced by a Trichoderma harzianum isolate with antagonistic activity against Crinipellis perniciosa, the causal agent of witches' broom of cocoa

An isolate of Trichoderma harzianum showing antagonistic activity against Crinipellis perniciosa, the causal agent of the witches' broom disease of cocoa, produces substantial amounts of hydrolytic enzymes. An amylase purified from isolate 1051 had a molecular mass of about 68.7 kDa. Maximal activity against soluble starch was determined at pH 4.0 and 60 degrees C. The K-m and V-max values were 3.5 mg ml(-1) and 1.67 mg min(-1) of reducing sugar. The end products were mostly malto-oligosaccharides. The enzyme also hydrolyzed glycogen, amylopectin, maltotriose, and maltotetraose, but not pullulan or cellobiose. Maltose was only barely hydrolyzed. The purified amylase exerted a discrete hydrolytic effect on the C. perniciosa cell wall in vitro as observed by scanning electron microscopic analysis. While Fe3+, Al3+, Zn2+, and Cu2+ were effective in inhibiting the purified amylase, Mn2+ considerably enhanced the activity. Ca2+, Mg2+, and Co2+ showed no substantial effect on enzyme activity. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.