This article reviews the molecular mechanisms of lytic enzymes produced by Trichoderma harzianum, a fungus used as a biological control agent against plant pathogens. T. harzianum attacks pathogenic fungi through mycoparasitism—secreting hydrolytic enzymes including chitinases, glucanases, and proteases that degrade fungal cell walls. The authors detail multiple chitinolytic enzymes (chitinases and N-acetylglucosaminidases) induced when T. harzianum grows on chitin as its sole carbon source, along with β-glucanases that target structural components in fungal cell walls. These enzymes are regulated during mycoparasitic interactions—recognition between T. harzianum and host fungi triggers specific morphological changes and coordinated enzyme induction. Research demonstrates that different chitinases and glucanases exhibit synergistic antifungal activity when combined, inhibiting spore germination and growth of various pathogenic fungi. The article emphasizes that successful biocontrol depends on understanding how T. harzianum recognizes pathogens, regulates enzyme production, and coordinates multiple enzyme activities for cell-wall degradation. This knowledge enables genetic improvements to enhance biocontrol agent effectiveness and reliability.

Key findings

• T. harzianum produces multiple chitinolytic enzymes (at least 8 different chitinases and glucosaminidases) that are specifically induced during growth on chitin or when interacting with fungal pathogens
• Recognition events between T. harzianum and host fungi trigger coordinated expression of specific combinations of cell-wall-degrading enzymes, including chitinases, glucanases, and alkaline proteases
• Purified lytic enzymes from T. harzianum exhibit direct antifungal activity, with synergistic effects when multiple enzymes are combined, particularly chitinases and β-glucanases acting on fungal cell walls
• Gene cloning studies have identified and characterized at least two endochitinase genes (ech-42 and chit33) and one β-glucanase gene from T. harzianum, with evidence of post-translational processing and specific induction mechanisms