Studies on the gushing potential of Penicillium expansum.

Gushing describes the spontaneous excessive over-foaming of carbonated beverages leading to considerable economic losses and reputational damages to the beverage industry. Surface-active proteins produced by filamentous fungi are involved in the induction of gushing. In the current study, the role of Penicillium expansum in sparkling wine gushing was investigated. Almost 40 P. expansum strains were analyzed regarding their ability to secrete surface-active proteins and to induce gushing in carbonated water as a model system and in sparkling wine. The majority of the strains produced surface-active compounds and induced gushing. The severity of gushing depended on the volume of culture supernatant added to carbonated liquids. Moreover, sparkling wine showed more severe gushing than carbonated water. A protein with a molecular mass of 20 kDa was prominent in gushing-inducing P. expansum culture supernatants. It was identified as PEX2_044840 from P. expansum. This protein was heterologously expressed in Pichia pastoris (Komagataella phaffi). The purified recombinant protein induced gushing in sparkling wine after addition of at least 30 µg/mL of protein sample.

Development and optimization of a loop-mediated isothermal amplification (LAMP) assay for the species-specific detection of Penicillium expansum.

Penicillium expansum is the main cause of Blue Mold Decay, which is the economically most significant postharvest disease on fruits. It occurs especially on pomaceous fruits such as apples and pears but also on a wide range of other fruits such as grapes or strawberries. Besides its negative economic effects on the industry, the fungus is also of health concern as it produces patulin, a mycotoxin known to provoke harmful effects in humans. A specific and rapid detection of this fungus therefore is required. In the current study, a loop-mediated isothermal amplification (LAMP) assay was developed and optimized for the species-specific detection of P. expansum. The assay showed high specificity during tests with genomic DNA of 187 fungal strains. The detection limit of the developed assay was 25 pg genomic DNA of P. expansum per reaction. The assay was successfully applied for the detection of the fungus on artificially contaminated apples, grapes, apple juice, apple puree, and grape juice. The developed assay is a promising tool for rapid, sensitive, specific, and cost-efficient detection of P. expansum in quality control applications in the food and beverage industry.