Fungal metabolism of butter and shea oils by Penicillium roquefortii in solid state cultures

Monoacylglycerols (monoglycerides, MAGs) were produced from butter oil and shea stearin fraction (shea oil) by two strains of Penicillium roquefortii, FRR 2456 (isolated from a spoilt melon) and Wisbey PJ (a commercial dairy strain), at pH 7.0 at 10 and 25 °C. The system was designed as a model of cheese using modified Czapek medium in solid state cultures. Shea oil with its unique fatty acid profile (stearic, oleic and palmitic acids) was used for comparison with butter oil. Yields of MAGs, which ranged from 3 to 14 g kg^-1 oil, were higher with butter than with shea oil and higher when the spoilage strain FRR 2456 was used. Monoacylglycerols produced by mycelium-bound lipases from both fungal strains were mainly sn-1(3) or isomers (60-70 mol%). Monopalmitin was the major MAG produced from both butter and shea oils. The production and use of MAGs alone or in combination with free fatty acids (FFAs) as food preservatives are discussed. It is implied that sn-1(3) MAGs together with free fatty acids may be part of a natural antimicrobial system in relatively high-pH foods such as blue mould-ripened cheese where growth of foodborne pathogens such as Listeria monocytogenes can be a problem