ASSIMILATION OF INGREDIENTS BY MICROORGANISMS 859 As shown in Table III, the bacteria isolated from cosmetics and stud- ied were mainly classified as the Genus Bacillus and Pseudomonas. Some species of Pseudomonas exhibited a strong affinity to assimilate these se- lected materials. Most of the yeasts (Table IV) were classified into the Genus Candida and also demonstrated a strong affinity to assimilate these materials. Among the fungi (Table V), many species of Penicillium were found which demonstrated a strong ability to assimilate these materials. The assimilabilities of some genera of microorganisms are shown in Table VII. The typical growth curves of yeasts in the medium containing LP-1 (Fig. 3) demonstrate that the adaptation of yeast against liquid paraffin is different among strains. Some of them had a short lag time and others a long one. Inducible enzymes appear to be operative in the utilization of liquid paraffin. Various types of liquid paraffin are used in cosmetic formulations. The utilization of representative liquid paraffins by Candida SY-15 is shown in Table VIII. This organism utilized the tested liquid paraffin fairly well but the cell growth became poor as the viscosity of liquid paraffin increased. It may be expected that highly viscous liquid paraffin is composed mainly of isoparaffins or naphthenes and it can be noted that Candida SY-15 hardly utilized them. The infrared absorption spectrum of the extract is shown in Fig. 4. Absorption at 1710 -• cm indicates the presence of carboxyl group. Figure 5 shows one of the results obtained by the GLC technique. The upper chromatogram is the initial composition of liquid paraffin (SHP-160), and the lower chromatogram shows the same liquid paraffin after incubation. The sharp peaks correspond to n-alkanes. The peak Table VII Assimilability of Some Genera Class Genus Sum of Materials Utilized Bacteria Bacillus Pseudomonas Yeast Pichia Candida Fungi Aspergillus Penicillium Cladosporium 2-4 14-16 11 12-16 8-13 12-15 10

860 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS /A 0.4 ./' 0 / / / 0.3 / / / 0.2 to ,-• / . ' / / i , , • ß 6 8 10 Oays Figure 3. Growth curves of various yeasts in medium containing liquid paraffin (paraffin- rich) Table VIII Utilization by Candida SY-75 of Several Liquid Paraffins Used as Substrates Vis- Trade cosity Name Manufacturer Composition (cps) Growth a SHP-160 Union Carbide Corp. Paraffin-rich 8.4 Crystol-70 Esso Standard Oil Co. Paraffin-rich 13.6 Ltd. Blandol Witco Chemical Corp. Paraffin-rich 16.5 Sonneborn Div. SHP-280 Union Carbide Corp. Paraffin-naphthene 25.2 Drakeol-35 Pennsylvania Refining Naphthene-rich 74.0 C•o. Symbols: d-d-, abundant growth d-, moderate growth q-, slight growth. height o[ n-alkanes (C14-C19) decreased sharply after incubation. It can be noted that Candida SY-15 utilizes n-alkanes in liquid paraffin as the carbon source and converts a terminal methyl gn'oup to a carboxyl group. The relationship between microbial assimilation and the chemical structure of substrate was studied using selected esters. The esters used as well as the results obtained with Pseudomonas No. 23 are shown in Table IX. These esters consisted of straight-chain compounds and the basic group (myristic acid, adipic acid, or glycerol) was utilized easily by the test microorganism. However, in the case of branched chains which were bound to the basic compound, the utilization was poor as the ester