Exploring malted barley waste for fungi producing surface active proteins like hydrophobins

Abstract

Malted barley waste is a rich source of different fungi. Hydrophobin like surface active proteins can be isolated from these fungal species and can be studied for industrial applications. In this study total 50 fungal strains were isolated from malt waste and screened for production of hydrophobin like protein (HYD-LP). Fungi producing highly hydrophobic spores were selected for fermentative growth. Ten such strains have shown good foam stability with half decay time more than foam of 0.1% SDS. Fungal strain S7-5 (Penicillium species close to P. islandicum) was selected for isolation of HYD-LPs which had lowered the surface tension of fermentation media to 31.046 mN/m with high half decay time of foam and good emulsification capacity. SDS-insoluble HYD-LP was purified using trifluroacetic acid. SDS-PAGE confirmed presence of low molecular weight protein (15 kDa) isolated from spore walls and fermentation broth. This protein was partially characterized as HYD-LP by performing RP-HPLC and studying its amphipathic nature as it has made low contact angle with Teflon surface. It also formed stable layer on Teflon surface and spore wall HYD-LP decreased hydrophobicity of Teflon by lowering contact angle (CA) of water by 21.63% and HYD-LP isolated from fermentation broth lowered water CA by 37.62%. This study is first to report the bio prospecting of fungi isolated from malted barley waste for biosurfactant characteristics and subsequent isolation of HYD-LP from strain close to Peniclliumislandicum.