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Int J Mol Sci. 2019 Jul 2;20(13). pii: E3242. doi: 10.3390/ijms20133242.

Characterization of a Surface-Active Protein Extracted from a Marine Strain of Penicillium chrysogenum.

Author information

1
Department of Chemical Sciences, University of Naples (Federico II), Via Cinthia, 80126 Naples, Italy.
2
Institute for Microelectronics and Microsystems, Unit of Naples-National Research Council, Via P. Castellino 111, 80127 Naples, Italy.
3
Department of Chemical Sciences, University of Naples (Federico II), Via Cinthia, 80126 Naples, Italy. giardina@unina.it.

Abstract

Marine microorganisms represent a reservoir of new promising secondary metabolites. Surface-active proteins with good emulsification activity can be isolated from fungal species that inhabit the marine environment and can be promising candidates for different biotechnological applications. In this study a novel surface-active protein, named Sap-Pc, was purified from a marine strain of Penicillium chrysogenum. The effect of salt concentration and temperature on protein production was analyzed, and a purification method was set up. The purified protein, identified as Pc13g06930, was annotated as a hypothetical protein. It was able to form emulsions, which were stable for at least one month, with an emulsification index comparable to that of other known surface-active proteins. The surface tension reduction was analyzed as function of protein concentration and a critical micellar concentration of 2 μM was determined. At neutral or alkaline pH, secondary structure changes were monitored over time, concurrently with the appearance of protein precipitation. Formation of amyloid-like fibrils of SAP-Pc was demonstrated by spectroscopic and microscopic analyses. Moreover, the effect of protein concentration, a parameter affecting kinetics of fibril formation, was investigated and an on-pathway involvement of micellar aggregates during the fibril formation process was suggested.

KEYWORDS:

amyloid fibrils; biosurfactant proteins; emulsions; marine fungi

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