Penicillium solitum

Penicillium solitum is an anamorphic, mesophilic, salinity-tolerant, and psychrotolerant species of fungus in the genus Penicillium. It is known to produce various compounds including polygalacturonase, compactin, cyclopenin, cyclopenol, cyclopeptin, dehydrocompactin, dihydrocyclopeptin, palitantin, solistatin, solistatinol, viridicatin, viridicatol.

P. Solitum forms dark blueish-green colonies that measure 22–28 mm in diameter on Czaek yeast extract agar, while on malt extract agar, it appears brownish orange. This distinct orange-brown color sets P. solitum apart from other similar Penicillium species,   making it useful for differentiation. The fungus has been historically isolated from various sources, including cheese rinds,  cured meats, and the Antarctic environment. It was specifically isolated from air-dried lamb thighs on the Faore island. During the production of traditional Tyrolean smoked and cured ham, both Penicillium solitum and Eurotium rubrum are commonly found.

Furthermore, Penicillium solitum is known to be a pathogen of pomaceous fruit, P. solitum causes blue rot in pome fruits through its production of polygalacturonase, which breaks down the apple’s cell wall.