Abstract: Two kinds of new natural microorganism source preservatives nominated Streptococus thermophilus Ferment and Aspergillus Ferment were taken as the object for research work.Formulation study based upon the bacterial inhibition action of the aforesaid preservatives was carried out.With reference of the bacterial inhibition efficacy test method of the American Personal Care Product Committee (PCPC),microbial challenge tests for emulsion formulations were processed.The test results demonstrated that an emulsion consisting of Streptococus thermophilus Ferment at 0.5% of mass fraction and Aspergillus Ferment at 0.3% of mass fraction can reduce the amount of microbial to be lower than 100 CFU/g on the 14th day and can pass the microbial challenge test meanwhile.

Key words: natural preservative, microorganism source, antimicrobial activity, microbial challenge test