The knowledge in microorganisms is still in its infancy, opening the way to multiple novelties. Moreover, microorganisms have singular metabolism and show great adaptability potential to survive under different stresses through the production of specific molecules. Hence, used as natural raw materials, they offer an immense potential resulting from their diversity and metabolism. By selecting microorganisms, known for their ability to produce molecules of interest or to resist to specific stresses, and by developing dedicated bioguiding processes, SILAB proposes innovative and efficient natural active ingredients. We can detail three examples of applied developments using bioguided microorganisms (i.e. yeast or bacteria) to obtain innovative natural active ingredients dedicated to the care of dehydrated or deficient skin as well as skin with pigment defects.

The first example refers to a development conducted to address skin dryness (1, 2). In this context, special attention was paid to Lactobacillus arizonensis, a probiotic strain from jojoba, known for its ability to adapt to extreme dry conditions. The natural environment of this bacteria was reproduced by adding jojoba to the culture medium to mimic the partnership existing between this bacterium and its substrate and incite it to produce the metabolites required for its survival and its adaptation. In comparison to a L. arizonensis culture without added jojoba or to a jojoba extract alone, bioguiding this bacterium induces the bioconversion of jojoba into a postbiotic rich in cyclic polyols. Interestingly, the resulting postbiotic active ingredient shows an efficacy on the quality of dry skin. Indeed, it reinforces the integrity of the cutaneous barrier while preserving the balance of the cutaneous microbiota.

As part of another development, a study was first carried out to define the needs of deficient skin, with the aim of providing a solution to restore their vitality (3). Then, the company selected Sphingomonas panaciterrae, a bacterium found in the rhizosphere of ginseng. Indeed, ginseng is known to impose many modifications and deficiencies on its environment, adversely affecting the availability of nutrients. To survive in this hostile environment, Sphingomonas panaciterrae implements protection mechanisms, in particular the production of exopolysaccharides (EPS) of the sphingans family, a property that SILAB decided to beneficially use. To reproduce the nutritional deficiency caused by ginseng to this bacterium, SILAB developed an innovative bio-inspired process, mimicking a nitrogen deficiency by glutamate depletion. This bioguided deficiency process led to a 2.4-fold increase in sugar production. The uniqueness of this approach was also validated by studying two other bacteria of the genus Sphingomonas, obtained from the root environment of ginseng (S. kyeonggiensis), or peach trees (S. pruni). When the same process was applied to these two strains, the sugar fraction responsible for the efficacy of the natural active ingredient could not be obtained. This comparative study therefore validated the choice of a microorganism of interest, in this example, Sphingomonas panaciterrae, as the producer of oligosphingans of interest for cutaneous vitality. By reactivating the biological pathways in deficient skin, the resulting natural active ingredient restores the skin's "vitality signature". The cellular metabolism is thus stimulated, and the quality of the cutaneous barrier reinforced. Tested on young and mature Caucasian volunteers, the active ingredient enhances complexion radiance and improves hydration from 7 days of application.

A third example could be detailed for the care of skin with pigment defects. Indeed, sulfur-containing molecules are well described for their capacity to limit the different steps of melanogenesis, which is the biological process behind the appearance of pigmentation spots. In this context, the company identified the yeast Ogataea siamensis, because it can metabolize the rare nutrients present on the aerial parts of its host plant thanks to the production of sulfur-containing molecules. To boost this intrinsic property, the company developed a bioguiding process by adding cysteine, an amino acid with a sulfur atom, indispensable precursor to produce sulfur-containing molecules. This metabolic engineering approach required to define several parameters including the dose of inducer and the moment and duration of the induction. The production of molecules of interest was followed thanks to the quantification of glutathione, a sulfur-containing peptide. The bioguiding process applied to Ogataea siamensis increases the glutathione production 6-fold compared to the original process. Moreover, SILAB demonstrated that Ogataea siamensis is the yeast producing the highest level of glutathione compared to three other yeasts collected on the aerial part of various flowers submitted to the same induction protocol. The resulting natural active ingredient, composed of sulfur-containing peptides is able to limit the production of melanin by Caucasian and Asian melanocytes. The appearance of spots is attenuated, complexion uniformity is improved, and complexion radiance is revived (4).

Hence, these three applied examples of microorganisms bioguiding reveal thatbiotechnology offers an immense potential to develop innovative and customized natural active ingredients, while preserving biodiversity.