REMI technique was used to construct mutants with improved cyanide-degradation ability from biocontrol fungus Trichoderma koningii strain T30. The plasmid pV2 transformation was confirmed by PCR and Southern blot analysis. Out of 21 transformants, 15 single-copied transformants (71.4%) were found. To compare enzyme activities of rhodanese and cyanide hydratase, T atroviride T23, T harzianum T21 and their transformants constructed by REMI previously were also included. Transformants TkB6 (0.173 pmols thiocyanate formed min(-1) mg protein(-1)) from T30 and TaK1 (0.174 gmols thiocyanate formed min(-1) mg protein) from T23 showed higher rhodanese activity than other transformants and their wild strains. TkA9 (5.53 mu mols formamide formed h(-1) mg protein(-1)) from T30 and Th64 (5.35 mu mols formamide formed h(-1) mg protein(-1)) from T21 had higher cyanide hydratase activity than other transformants and their wild strains. (C) 2006 Elsevier Ltd. All rights reserved.