Fungal hydrophobins render stones impermeable for water but keep them permeable for vapor

Abstract

The conservation of architectural heritage is a big challenge in times with increasing air pollution with aggressive gases. A second major threat to buildings is the combination of water and air contaminants which may be used by microorganisms for their metabolism. Hence, myriads of different bacteria and fungi populate stone surfaces and penetrate into the fine pores and cracks. Whereas epoxid-based paintings (or other paintings) may protect the coated surfaces from water and aggressive gases, these chemicals seal the stone surface and prevent also the evaporation of vapor from the inside of the buildings. Here, we tested a natural, fungal protein-based coating method. Fungi use small, amphiphilic proteins to turn their surfaces hydrophobic. We found that Aspergillus nidulans hydrophobin DewA and Trichoderma reesei HFBI confer hydrophobicity to stones but keep their pores open. The effect resembles “Gore-tex” fabric material.

Stone sustainable protection and preservation using a zein-based hydrophobic coating

“…Thus, zein applied by spray coating seems to confer a good degree of water repellency to the stone. Water contact angle is comparable to the one obtained with other natural-based coating, such as poly(hydroxyalkanoate)s [24] or fungal hydrophobines [25]. Results obtained in terms of water repellency are even improved with respect to commercially available polysiloxanes coatings [72], which gave a water contact Fig.…”

“…Recently polymers from natural sources have attracted interest as protective materials for stones, as sustainable alternatives to the synthetic coatings, but also due to the possibility of easier removal from the stones' surface. Up to now, the protection properties of zein, chitosan, poly(lactic acid) (PLA), poly(3-hydroxybutyrate) (PHB) [22,23], poly (hydroxyalkanoate)s (PHAs) [24], and fungal hydrophobines [25] have been investigated. However, research in this field is still in a preliminary stage.…”

Development of Multifunctional Coatings for Protecting Stones and Lime Mortars of the Architectural Heritage

“…Different strategies of achieving water repellency have been proposed and discussed (Tserepi, Vlachopoulou and Gogolides 2006;Manoudis et al 2009). Most of them are based on the application of organic compounds: resins, acrylate-based compounds, waxes … (Alessandrini et al 2000;Toniolo et al 2002;Fermo et al 2014;Andreotti et al 2018;Aslanidou, Karapanagiotis and Lampakis 2018;Winandy, Schlebusch and Fischer 2019). Different anti-graffiti treatments depending on the easiness of their removal after several cleaning processes have been tested by Macchia et al (2019).…”

A class I hydrophobin inTrichoderma virensinfluences plant-microbe interactions through enhancement of enzyme activity and MAMP recognition

“…Beyond its biological role in the fungus, HFB9A could present a possibility for application in an industrial setting. Fungal hydrophobins are increasingly being used in commercial applications, such as in the protection of historic stonework from water damage (Winandy et al, 2019). The cellulase and chitinase enhancement activity of HFB9A makes it a viable candidate for industrial applications, e.g.…”