A New Approach to Cosmetic Microbiology Testing

Development of a 24-Hour ATP-Bioluminescence Amplification Method for Cosmetic Microbiology Testing and Release of the Group Standard

Microbial testing is a critical component of cosmetic safety evaluation. However, current domestic and international standard microbial test methods for cosmetics rely solely on traditional cultivation techniques. These methods require separate testing protocols for total plate count, total mold and yeast count, heat-resistant Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, with manual result interpretation. The testing cycle spans at least 5 days (as detailed in China's Cosmetics Safety and Technical Specifications [2015 Edition]), resulting in prolonged detection times, low efficiency, and an inability to meet the demands of rapid product release. Developing efficient and accurate rapid microbial detection technologies has become an urgent industry priority.

To address this, a consortium comprising the China National Research Institute of Food and Fermentation Industries, Procter & Gamble (China) Co., Ltd., Unilever (China) Co., Ltd., National Institutes for Food and Drug Control, and Charles River Microbial Solutions (Shanghai) Co., Ltd., established a project team. The team developed a 24-hour amplified ATP-bioluminescence method for cosmetic microbial testing using a dual-culture system combined with post-enrichment assay. This approach enables synchronized detection of 5 standard microbiological indicators within 24 hours. The group standard T/CAFFCI 46-2024 Qualitative Detection of Microorganisms in Cosmetics—Amplified ATP-Bioluminescence Method was subsequently formulated and released, facilitating the practical application of research outcomes.

Technical Principles
This technology leverages adenosine kinase (AK) within microorganisms to catalyze the conversion of externally added adenosine diphosphate (ADP) into adenosine triphosphate (ATP), achieving enzyme-enhanced ATP detection. By introducing luciferase and luciferin, the energy released during ATP hydrolysis is converted into bioluminescent signals, which are measured using an automated luminometer. The presence of microorganisms in samples is determined based on bioluminescent signal intensity.

The Celsis^® rapid microbial detection system employed in this method offers advantages such as rapid operation, high sensitivity, automated reporting, high throughput, and efficiency. Its application in testing cosmetic raw materials, production environments, intermediate products, and finished products enables rapid, accurate identification of microbial contamination risks, yielding significant economic benefits. In recent years, this method has been adopted by international pharmaceutical companies as an alternative for sterile product testing and rapid release.

Research

1. Development of the 24-Hour Detection Based on Amplified ATP-Bioluminescence Method
   Slow-growing and fastidious cosmetic-related strains were collected. Building on a previously established co-enrichment system for bacteria, yeast, and molds, experiments optimized key parameters including incubation temperature, nutrient composition, pH, and cell lysis methods. Dual-culture systems for rapid bacterial and fungal enrichment were developed, enabling simultaneous qualitative detection of bacteria, molds, and yeasts in samples within 24 hours.
   
   To assess the method’s broad applicability in cosmetic microbiology, 108 bacterial, mold, and yeast strains from cosmetic raw materials and production environments were gathered through literature review and taxonomic/growth characteristic analysis for growth promotion testing.
   
   
2. Validation Against Cosmetics Safety and Technical Specifications
   Six commercial cosmetic products with varying efficacy claims, application sites, formulations, usage methods, and preservative systems were selected based on Cosmetics Classification Rules and Catalog and GB/T 18670-2017 Cosmetics Classification.
   
   Validation followed the Chinese Pharmacopoeia (2020 Edition) guidelines for alternative microbiological methods. Specificity, limit of detection (LOD), ruggedness, and robustness were evaluated for Escherichia coli CICC 10389, Staphylococcus aureus CICC 10384, Pseudomonas aeruginosa CICC 10419, Bacillus subtilis CICC 10275, Candida albicans CICC 1965, and Aspergillus niger CICC 2487. Results demonstrated superior LOD for the ATP method compared to standard techniques (p < 0.0001), with enhanced enrichment and sensitivity for slow-growing strains. The method demonstrated equivalent specificity, ruggedness, and robustness, qualifying it as an alternative to traditional plate count methods.
   
   Equivalence validation for E. coli, P. aeruginosa, and S. aureus detection against standard methods confirmed the ATP method’s superior LOD (p < 0.0001) and ability to complete synchronized qualitative testing within 24 hours, offering practical benefits for cosmetic microbiology laboratories.
   
   
3. Product Suitability in Cosmetic Testing
   Product Suitability was further assessed through sample interference tests and inoculation trials on 56 commercial cosmetics (general and special use) from 20 domestic/international brands spanning diverse functions, application sites, and formulations. Results confirmed the method’s broad applicability across cosmetic products.

Project Outcomes and Significance
Systematic validation confirmed the 24-hour ATP-bioluminescence method’s technical advantages, including high sensitivity and efficiency with superior specificity, reproducibility, and robustness compared to Cosmetics Safety and Technical Specifications (2015). The method reduces microbiological testing cycles from ≥5 days to 24 hours, enabling rapid screening of microbial contamination in production monitoring and final product release. This provides a scientific basis for integrating ATP-bioluminescence into comprehensive microbial safety control across cosmetic manufacturing.

The formulation and implementation of the group standard offers standardized solutions for enterprises requiring rapid results. By establishing a rigorous methodological framework, it reduces validation costs while ensuring compliance and technical reliability. Feedback from implementing enterprises indicates full regulatory compliance within 1–2 months, accelerating technology commercialization and achieving cost efficiency and increased business value. This standardization pathway supports high-quality industry development by optimizing processes and facilitating technology adoption.

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