Bioproduction of Class II hydrophobins with unique biospecific functionalities using Trichoderma species

Hydrophobins (HFBs), produced by filamentous fungi, are amphiphilic cysteine-rich proteins of relatively low molecular weight showing unique physicochemical properties. HFBs are considered the strongest surface active proteins from microbial origin. By self-assembling at hydrophobic-hydrophilic interfaces, HFBs form an amphiphilic membrane and consequently reduce water surface tension and stabilize foams and emulsions at low concentrations. HFBs are also highly appreciated due to their ability to change the polarity of surfaces. HFBs are divided in two classes, namely Class I and Class II HFBs, based on differences in their hydropathy plots and solubility and morphology of the membranes, formed at interfaces. This study focused on Class II HFBs due to their exceptional high surface elasticity and easier purification compared to Class I HFBs, making them of significant economic value for personal care, pharmaceutical, medical and food applications. Industrial applications currently remain lacking despite their great potential due to a low production yield. Therefore, the goal of this study was to study the effect of several process parameters on the bioproduction of Class II hydrophobins, more specifically focusing on HFBI, expressed by Trichoderma reesei MUCL 44908, and Class II HFBs produced by IHEM 5437 belonging to the Trichoderma harzianum species complex.