Conversion of triacylglycerols into monoacylglycerols by penicillium roquefortii

The synthesis and use of monoacylglycerols in food systems havc been reviewed. The use of monoacylglycerols alone or in combination with free fatty acids as food preservatives has been discussed. Model systems have been devised to produce monoacylglycerols (MAGs) from butter and Shea oils with two strains of Penicillium roquefortii, FRR 2456 (isolated from a spoilt melon) and Wisbey PJ (a commercial dairy strain) A semi-micro method was developed using Preparative Thin Layer Chromatography (PTLC) and Gas Chromatography - Mass Spectrometry (GC-MS) of the MAG trimethylsilyl ether derivatives to determine the identification, fatty acid composition and structural isomers of the individual MAG. The main monoacylglycerols produced by spores and emerging mycelium were 1(3)-monoacylsn-lycerols (in suspension culture). Monopalmitin was the major MAG from butter and Shea oils. Monoacylglycerols produced by fungal mycelium (in solid-state culture) were mainly the 1 (3 )-monoacyl-sn-glycerols although approximately 30% were present as 2-monoacyl-snglycerols. Again the main MAG was monopalmitin. It suggested that P. roquefortii produced two lipases, one during germination with specificity to the sn-2 position in the original triacylglycerols (TAGs) and one L3-specific during growth of the fungal mycelium. In addition, flavour compounds, methyl ketones and y-lactones, were found in solid-state culture. The composition of the MAGs formed by lipolysis using a commercial lipase (E.C.3.1.1.3) with 1,3- specificity gave the expected 2-isomers when butter oil was the substrate but gave 1 (3)monostearin rather than the expected 2-monoolein when Shea oil was the substrate. It suggested that acyl migration occurred due to the reactive nature of the original oleate group at the sn-2 position in the Shea oil TAGs. There were no significant differences with fungal strain or temperature of incubation (10 °C and 25°C) on the composition of the MAGs. The mechanism of formation of MAGs from butter and Shea oils has been discussed. It has been suggested that l(3)-MAGs together with free fatty acids may be part of a natural antimicrobial system in high pH foods such as blue mould-ripened cheese where growth of foodborne pathogens such as Listeria monoGytogcnes can be a problem from time to time