74 PRESERVATIVES
Natural antimicrobials for a post-biotic future
n Anna Crovetto – Active Micro Technologies, Italy
The synergy between the skin and its individual network of commensal microflora is a trending topic and the market is quickly becoming saturated with different probiotic products targeted towards skin care. However, there is a distinct conflict between the addition of live bacteria to a formulation, the legal requirements of a safely preserved cosmetic product and the subsequent effects on sensitive skin and the microbiome. With consumer and regulatory pressure changing how people seek to preserve products, not just in personal care but across many markets ranging from food to fertilizers, emerging ‘non-preservative’ technologies are taking centre stage.
The challenge In personal care, we use preservatives in order to prevent microbial contamination of a product during its foreseeable life in use by the end consumer. In Europe, we have a clearly defined list of permissible preservatives as described in Annex V of the EU Cosmetics Directive. These more traditional preservatives are highly effective and relatively easy to use. So, formulators have grown very comfortable with this list and can preserve a product without much adjustment or tinkering to the formulation. Although these systems are extremely effective at keeping a product clean and safe none are intelligent enough to distinguish between the ‘bad’ bacteria, that can contaminate a cosmetic product, and the ‘good’ bacteria, of the skin microbiome. There is also a constant battle between
the effectiveness of a preservative, exposure and risk. As the industry adopts the same preservative systems, the exposure to the consumer is increased and, so is the risk. Sensitization issues become enough that the preservative has to be removed from the market and we have seen this happen several times over the last years with materials like triclosan, parabens and soon maybe phenoxyethanol as well. Our choice or ‘palette’ of allowed preservatives is rapidly disappearing. One of the biggest challenges for the personal care industry is to find many
PERSONAL CARE NORTH AMERICA
different preservative options in order to prolong the life span of these systems and reduce over exposure and risk of sensitization to the consumer. As if this is not enough, these actives should also be effective at protecting formulations from pathogenic growth while causing minimal disruption to the commensal microflora that exists in symbiosis with the skin. To answer this challenge a novel approach, offered by Active Micro Technologies, is to capture the natural defence strategy of a commensal probiotic bacteria in a commercially viable cosmetic active form. The key priority is and continues to be the same; to produce safe and effective cosmetic products.
Technology Lactobacilli are Gram-positive bacteria of the family Lactobacillaceae, characterized by their ability to produce lactic acid as a by-product of glucose metabolism. Lactobacillus are commensal inhabitants of the human gastrointestinal tract and commercial preparations of lactobacilli are used as popular probiotics to restore normal flora balance following a course of antibiotic treatments. The probiotic strain Lactobacillus
acidophilus is used to produce many fermented foods and is a common starter culture for yogurt production. Like many members of the lactic acid bacteria family, Lactobacillus acidophilus is capable of restricting pathogenic growth by acidifying its environment. In addition, Lactobacillus acidophilus produces novel antimicrobial peptides, known as bacteriocins. These peptides can be described as postbiotics;
Table 1 MIC
E. coli S. aureus
P. aeruginosa C. albicans
A. brasiliensis %
0.50 0.50 0.50 0.50 0.50
Figure 1:MIC results for the Lactobacillus Ferment.
non-viable metabolic by-products from a probiotic microorganism that have a biological activity in the host. Bacteriocins are composed of a relatively
short amino acid sequence. They function as a defensive system by having an affinity for the microbial membranes and cell walls of competitive microbial species. Once the peptides have associated with the cell, they create pores that interfere with the cell’s ability to regulate the osmotic balance between itself and its external environment. Typically, there is leakage of cytoplasmic material out of the cell and an influx into the cell of water and salts from the environment. The end result is either total cell disruption or significant interference with the cell’s metabolic processes, which in either case results in cell death. These peptide molecules expressed by bacteria are often used in the production of antibiotics and this activity can now be harnessed for use in personal care. To produce sufficient bacteriocin
peptides to give a functioning cosmetic active the Lactobacillus acidophilus is cultured in a defined growth medium, which is free from any synthetic or animal derived components. The bacteriocins are produced within the Lactobacillus cell and are transported through the cell membrane. Normally the peptides are not released fully, so the cells are lyzed to enable complete release. The ferment system is filtered to remove any viable microorganisms and the peptide postbiotic based active is created. The final raw material, INCI: Lactobacillus Ferment, is standardized for a bacteriocin content of 5 – 10%, but is free from any live cell material.
Activity demonstrated The next stage in the development of this antimicrobial ferment was to determine the product’s potential ability to inhibit the growth of bacteria, yeasts and molds. Using standard serial dilution protocols in growth media, the Minimum Inhibitory Concentrations (MICs) were determined for bacteria, yeast and mold organisms. As shown in Figure 1, these positive MIC
May 2020
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