Scedosporium aurantiacum is an opportunistic filamentous fungus increasingly isolated from the sputum of cystic fibrosis patients, and is especially prevalent in Australia. At the moment, very little is known about the infection mechanism of this fungus. Secreted proteases have been shown to contribute to fungal virulence in several studies with other fungi. Here we have compared the profiles of proteases secreted by a clinical isolate Scedosporium aurantiacum (WM 06.482) and an environmental strain (WM 10.136) grown on a synthetic cystic fibrosis sputum medium supplemented with casein or mucin. Protease activity was assessed using class-specific substrates and inhibitors. Subtilisin-like and trypsin-like serine protease activity was detected in all cultures. The greatest difference in the secretion of proteases between the two strains occurred in mucin-supplemented medium, where the activities of the elastase-like, trypsin-like and aspartic proteases were, overall, 2.5–75 fold higher in the clinical strain compared to the environmental strain. Proteases secreted by the two strains in the mucin-supplemented medium were further analyzed by mass spectrometry. Six homologs of fungal proteases were identified from the clinical strain and five from the environmental strain. Of these, three were common for both strains including a subtilisin peptidase, a putative leucine aminopeptidase and a PA-SaNapH-like protease. Trypsin-like protease was identified by mass spectrometry only in the clinical isolate even though trypsin-like activity was present in all cultures. In contrast, high elastase-like activity was measured in the culture supernatant of the clinical strain but could not be identified by mass spectrometry searching against other fungi in the NCBI database. Future availability of an annotated genome will help finalise identification of the S. aurantiacum proteases.

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Peptidases secreted by a clinical high-virulence Scedosporium aurantiacum isolate (strain WM 06.482; CBS 136046) under normoxic and hypoxic conditions were separated via size-exclusion chromatography, and peptidase activities present in each fraction were determined using class-specific substrates. The fractions demonstrating peptidase activity were assessed for their effects on the attachment and viability of A549 human lung epithelial cells in vitro. Of the peptidases detected in the size-exclusion chromatography fractions, the elastase-like peptidase reduced cell viability, the chymotrypsin-like peptidase was associated with cell detachment, and the cysteine peptidases were able to abolish both cell attachment and viability. The loss of cell viability and attachment became more prominent with an increase in the peptidase activity and could also be specifically prevented by addition of class-specific peptidase inhibitors. Our findings indicate that peptidases secreted by S. aurantiacum can breach the human alveolar epithelial cell barrier and, thus, may have a role in the pathobiology of the organism.

Interactions between components in film‐forming solution affected the physicochemical properties of active packaging. A series of soy protein isolate (SPI)‐based nanocomposite films reinforced with zinc oxide nanoparticles and different pitaya peel extract (PPE) levels were fabricated by photocatalysis. Results showed that the tensile strength, oxygen and water vapor barrier properties, thermal stability and DPPH scavenging activity were substantially improved, but the elongation at break and transmittance decreased with the proportion of PPE increased due to the formation of a more compact film structure caused by the crosslinking of PPE and SPI, particularly at the SPI/PPE ratio of 1:2. However, excessive PPE was not conducive to the integrity and continuity of film structures. The SPI/PPE films had more favorable anti‐bacterial activities against Staphylococcus aureus than Vibrio parahaemolyticus. Therefore, our finding suggested that photocatalytic SPI/PPE nanocomposite film is an interesting alternative to obtain materials with antimicrobial and antioxidant properties. Novelty impact statement Pitaya peel extract (PPE) was added into soy protein isolate (SPI)/ZnO film matrix through photocatalysis. Addition of PPE resulted in compact inner microstructures of the films. SPI‐PPE conjugate greatly improved the antibacterial and antioxidant properties of the films.

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