CELLULAR FATTY ACYL AND ALKENYL RESIDUES IN MEGASPHAERA AND PECTINATUS SPECIES - CONTRASTING PROFILES AND DETECTION OF BEER SPOILAGE

The strictly anaerobic Gram-negative beer spoilage bacteria Megasphaer a cerevisiae, Pectinatus cerevisiiphilus and P. frisingensis were subj ected to cellular fatty acid analysis, employing acid- and base-cataly sed cleavage, gas chromatography and mass spectrometry. M. cerevisiae contained 12:0, 16:0, 16:1, 18:1, 17:cyc, 19:cyc, 12:0(3OH), 14:0(3OH) as the main fatty acids, and alk-1-enyl chains instead of acyl chains were detected to a considerable extent (14% of total fatty acids), in dicating the presence of plasmalogens. The fatty acid pattern of M. ce revisiae was almost identical to that of M. elsdenii, the only species previously assigned to this genus. P. cerevisiiphilus and P. frisinge nsis yielded fatty acids that were heavily dominated by odd-numbered c hains; 11:0, 15:0, 17:1, 18:cyc and 13:0(3OH) were the main fatty acid s detected in both species. Alk-1-enyl chains with similar chain lengt hs were also found. Both Pectinatus species contained six different 3- hydroxy fatty acids with chain lengths between 11 and 15 carbons, 13:0 (3OH) being dominant and the others accounting for generally less than 1% of total fatty acids. Among the minor components, an unsaturated 3 -hydroxy fatty acid was detected which was shown to be 13:1(3OH). In a ddition, fatty acid analysis was shown to be applicable to detection o f bacterial contamination of beer.