Expression of biotechnology-relevant hydrophobins HFB4 and HFB7 in Trichoderma

Abstract

Hydrophobins are small (7-12kDa) surface active proteins that are exclusively produced by filamentous fungi. Due to their amphiphilic properties they play important roles in fungal growth and interactions with the environment. Their remarkable biophysical properties, such as high surface activity and the formation of self-assembled structures have also raised considerable interest in the industrial application for processes requiring surface modification. The highest diversity of class II hydrophobins was found in the genus Trichoderma, commonly isolated mycotrophic fungi with a broad range of environmental adaptations. We have recently identified and characterized two new class II hydrophobins from T. virens, HFB4 and HFB7, which are able to stimulate the degradation of the thermoplastic polymer polyethylene terephthalate (PET) by cutinases (Espino-Rammer et al., 2013). Here their constitutive homologous overproduction in T. virens and constitutive heterologous overproduction in T. reesei is described. The bioactivity of the produced HFB4 and HFB7 was proven by their surface modulation activity on PET as a hydrophobic surface model and on glass as a hydrophilic surface model. Water contact angle measurements showed that the hydrophobic properties of PET were significantly altered. However, both HFB4 and HFB7 only slightly changed the hydrophilicity of glass.