154 JOURNAL OF COSMETIC SCIENCE groups that carry aniouic charges. A long fatty acid residue builds up the hydmphobic domain. The chain configuration varies in length and branching. The major species has twelve outer-ting ca•oon atoms with branching at its end as shown in Figure 1. Our product is a mixture of sodium salts of surfacfin with slightly different andno acid arrangements and fatty acid chains. Strong surface activity. It was continned in our laboratory that the critical ndcelle concentration (CMC) of suffacfin sodium salt was 3 !xM. Figure 2 shows the decrease of surface tension of various suffactant aqueous solutions. Such a low CMC of surfacfin is one of the lowest values of all ever-known detergents. Compared to sodium dodecyl sulfate (SDS), CMC of surfactin is one thousand times lower than that of SDS. Generally, nonionic detergents have much lower CIVIC than aniouic or cafiouic ones. It is noteworthy that Surfactin has a lower CMC than Triton X100. High stability of surfactin emulsion. Sorfacfin eml•Srm is very stable. In this experiment, A five-ndlliliter of squarane was emulsified with the same volume of 0.1% suffactant solutions using a mechanical emulsifier, and then incubated at 80øC for 60 days. The results are shown in figure 3. Only surfactin emulsion remained after such a long severe incubation. Therefore it was continned that surfactin emulsion was stable even at high temperature. The high stability of surfactin emulsion is quite likely owing to its large molecular size. Its molecular weight is about one thousand Dalton. Compared to other softactanls, it is relatively large. The massive molecular size contributes to stabilizing the ndcelle, as it requires more energy to move the arranged suffactin molecules building the ndcelle than other detergents. Low skin irritation. The primary skin irritation of Figure 3. Squarane emulsion at 80øC after 60 days surfactin was evaluated in rabbits. Sodium lauroyl glutamate (SLG) and SDS were also evaluated as the reference substances. Each substance was closed-patched on the skin of the animals and the obsen•ed eq, thema and edema were scored. The degree of irritation was compared by P.I.I. (primary irritation index a sum of scores for each substance divided by the number of animals). The results are shown in figure 4. Surfacfin showed a significantly low P.I.I. It is noteworthy that no irritation was obsen'ed at all at the concentration of 2.5%, which is the expected normal concentration in cosmetics. These results indicate that suffactin is far from imtative. Surfactin sodium salt is an auiouic lipopeptide bio- suffactant produced by ndcmorganisms. It has a unique chendcal structure and shows a strong surface activity. The emulsion of surfacfin is very stable. It is supposed that the stability is caused by its massive structure. Furthermore, soffactin shows an extremely weak skin irritation. These properties suggest the use of suffacfin suitable for cosmetics. References 1. Arima, K., Kakinuma, A., and Tamura, G. Blochem. Biophys. Research Corn. 31 (3), 488 (1968) o ø'r• o•! 029 ß $u•aclin I• 0.75 2. Kakinuma, A., Hori, M., lsono, M., Tamura, G., and Figure 4. A comparison of the primary skin irritation Arima, K. Agr. Biol. Chem. 33 (6), 971 (1969) 3. Kakinuma, A., Sugino, H., Isono, M., Tamura, G., and Arima, K. Agr. Biol. Chem. 33 (6), 973 (1969) 4. Kakinuma, A., Hori, M., Sugino, H., Yoshida, L, Isono, M., Tamura, G., and Arima, K. Agr. Biol. Chem. 33 (10), 1523 (1969) 5. Kakinuma, A., Hori, M., Sogino, H., Yoshida, I., Isono, M., Tamurn, G., and Arima, K. Agr. Bioi. Chem. 33 (11), 1669 (1969)