ASSIMILATION OF INGREDIENTS BY MICROORGANISMS 865 - lO 5 Figure 6. Chromatogram of glycerol tri-2-ethylhexanoate medium decreased as the bacterial growth increased. Monoglyceride and diglyceride appeared as the triglyceride diminished but their content did not increase appreciably. It may be supposed that mono- and diglyceride were utilized as the sole carbon source. Glycerides are thought to be nutritious to microorganisms. How- ever, the glyceride synthesized with branched-chain fatty acid was not utilized. The branched chain demonstrated a great resistance against microbial assimilation. Similar results were noted with fatty acids and esters. The biodegradability of branched-chain derivatives were studied with hydrocarbons (1-4) and alkyl benzene sulfonates (ABS) (5). As for ali- phatic hydrocarbons, it was reported that n-alkanes or n-alkenes were readily assimilated and the assimilation became more difficult as side- chain length increased. With ABS, it was found that the compounds with the phenyl •oup nearer the center of the chain were much more resistant than others with 2- and 3-phenyl isomers. The methyl group in the chain did not retard the degradation and little difference was noted

864 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS incubation 1 1o 5 Figure 7. Ghromatogram of glycerol tricaprylate pH 5 ['-,.,•., • 08' • O6 04 O2 O0 2 4 6 8 10 Days Figure 8. Degradation of glycerol tricaprylate •, -0- cell growth 60 • -V- pH • _•_ mono •_ _&_ di ,40 _ X _ tri l glycerid