Evolution and functional characterization of HFB7 : a novel family of class II hydrophobins from Trichoderma

Abstract

In recent years a group of small cysteine-rich proteins produced by filamentous fungi, so called hydrophobins, have been investigated for numerous industrial applications due to the remarkable properties they display as surface active agents. Their amphiphilic nature enables them to act as surface modifiers that can render hydrophobic surfaces hydrophilic or hydrophilic surfaces more hydrophobic. In this Thesis a new group of hydrophobins found in the genus Hypocrea/Trichoderma, (Hypocreales, Ascomycota) tentatively named HFB7, was studied for the application in poly (ethylene terephthalate) (PET) degradation by fungal enzymes such as cutinases. The genus Hypocrea/Trichoderma is known to have the highest number of hydrophbobin genes found so far, of which several have not been investigated yet.<br />HFB7 displays a biased occurrence in two clades of Section Pachybasium namely Harzianum Clade and T. virens respectively. A screening and subsequent sequencing of strains from both species revealed the structural diversity of HFB7 orthologues and evolution under positive selection pressure of the whole group. From the screened strains several structurally diverse HFB7 were selected for the production as a recombinant proteins with an N-terminal glutathione S-transferase-tag in Escherichia coli and prepared for tests in PET degradation.