Over the past several decades there has been growing public pressure,
increasingly strict chemical regulations, preservative sensitization issues,
and the potential for developing microbial resistance to the chemical
preservative products typically used in cosmetic and personal care
formulations. These factors have resulted in numerous methods of preservation
being pulled from the marketplace, despite being the products of choice at one
time. To offer a solution to this preservation paradigm, AMT has
developed a line of products based on naturally occurring compounds that
provide active cosmetic properties, but by their very nature are also capable
of providing product preservation. This antimicrobial capability is due to
natural mechanisms developed by plants and microorganisms by which they protect
themselves from their environment and other competing organisms.
Leucidal® Liquid is based on an antimicrobial peptide originally derived from the
lactic acid bacteria, Leuconostoc kimchii. L. kimchii is one
of 15 species of microorganisms that make up the mixed culture used for
producing the Korean dietary staple known as kimchi, a type of fermented
Like many lactic acid bacteria, L. kimchii is capable of
restricting the growth of other microorganisms by acidifying its environment,
but as is common in nature, it is not content to limit itself to a single
mechanism of defense. In addition to acidifying its environment, it also
produces a novel antimicrobial peptide. Using modern fermentation and
bioprocessing technology, AMT has commercialized this
antimicrobial peptide to produce Leucidal® Liquid.
A skin moisturization study was performed using an untreated control, generic
cream base, and an experimental with the same cream base containing 2.0% Leucidal®
Liquid. Comparative moisturization results from this study are shown in
Figure 1. As demonstrated by the results of this study, the addition of
2.0% Leucidal® Liquid improved moisture levels by 42.01% after
24 hours and by 62.33% after four weeks when compared to the untreated control.
When compared to the base cream Leucidal® Liquid improved
moisturization by 14.38% and after 24 hours and by 24.13% after four weeks.
Based on these results, adding this innovative product provides the formulator
the opportunity to capitalize on both the natural antimicrobial properties
of Leucidal® Liquid, as well as its ability to provide potent
moisturizing benefits to the cosmetic formulation. These properties make it
ideal for applications addressing numerous skin and scalp conditions.
One of the first steps in the development of this product was to determine the peptide’s potential ability to inhibit the growth of a variety of bacteria and fungi. Using standard serial dilution protocols in growth media, the Minimum Inhibitory Concentrations (MICs) for Leucidal® Liquid were determined for a variety of both bacterial and fungal organisms. The results of these tests are shown in Figure 2.
The positive MIC screening results warranted further testing to confirm its ability to provide product preservation. Double Challenge Tests were completed using either 2.0% or 4.0% Leucidal® Liquid in a generic cream base formulation at pH values of 3, 5, and 7. Samples were inoculated with E. coli, P. aeruginosa, S. aureus, C. albicans, and A. brasiliensis. During the first 28-day incubation period, samples were periodically collected and tested for the presence of these microorganisms. Following this initial 28 days of incubation, the cream samples were then re-inoculated with the microbial cultures and sampled over an additional 28-day period. Figure 3 shows the positive preservation results for 4.0% Leucidal® Liquid in a generic cream base formulation at pH 5.
A Time Kill Test was performed to determine the change in population of aerobic microorganisms within a specified sampling time when tested against 4.0% Leucidal® Liquid solution. The activity of the test material inoculated was evaluated at determine time intervals of 30 seconds, 1, 5, 10 and 30 minutes after the inoculation to determine quantitatively the number of viable microorganisms remaining after the incubation time. As shown in Figure 5, the Gram-positive and Gram-negative bacteria as well as the yeast and mold were reduced by 99.9% within 30 seconds interval of the test after the inoculation.
As with all biological materials, some attention must paid to the conditions under which Leucidal® Liquid is used. Based on bench-scale evaluations, as well as actual product applications, Leucidal® Liquid has been found to be effective over a wide range of typical cosmetic and personal care product manufacturing conditions. The product has been found to be heat stable up to 70°C and active under both acidic (pH 3) and basic conditions (pH 8).