Heterogeneous expression and emulsifying activity of class I hydrophobin from Pholiota nameko

Hydrophobins secreted by filamentous fungi self-assemble into an amphipathic film at hydrophilic/ hydrophobic interfaces. This unique property suggests that the hydrophobins have a high potential for industrial applications. However, the assemblages of class I hydrophobins are highly insoluble, making such commercial applications difficult. To enhance the solubility of class I hydrophobins, we have attempted to express class I hydrophobin PNH1 from Pholiota nameko fused with glutathione S-transferase (GST) in Escherichia coli. The GST–PNH1 was effectively isolated from the soluble fraction of transformed E. coli, and subsequent analysis revealed that the purified GST–PNH1 had almost the same emulsifying activity as PNH1.