# Nutritional and Medicinal Properties of Microbial Oil
## 6 Applications of Microbial Oils in Cosmetics, Pharmacy, and Medicine  
The scientific community is interested not only in the production of odd-chain fatty acids, but also in their potential applications. Research on the biological activity of acids with 15 and 17 carbon atoms in their molecules has been carried out for over 20 years. Bothcis-9-heptadecenoic and its 6-methyl derivative produced by _Pseudozyma floccosa_ exhibit antifungal activity against _Cladosporium cucumerinum_ and _Botrytis cinerea_, which are fungal plant pathogens. Interestingly, heptadecenoic acid primarily increase the fungal membrane permeability and cause cytoplasmic disintegration. As the authors pointed out, due to the difficulties in the extraction and isolation of odd-chain fatty acids from _P. flocculosa_, a chemical procedure for their synthesis was elaborated [86; 87]. In addition, some of the derivatives of odd-chain fatty acids, such as methyl heptadecanoate, are commonly used as internal standards for quantitative analysis, like the evaluation of the fatty acid composition through gas chromatography [28]. In addition, pentadecanoic acid serves as a marker for the intake of milk fat and other dairy foods, where it turns out that the consumption of butter and the total milk fat intake are positively correlated with the levels of C15:0 in serum cholesterol esters; moreover, an inverse association between diabetes risk and this odd-chain fatty acid in a multiethnic cohort study was observed [88; 89; 90]. Other studies have confirmed the usefulness of pentadecanoic acid as a biomarker in non-alcoholic steatohepatitis; in addition, the authors have confirmed, throughout in vivo studies on mice, that the deficit of C15:0 in methionine and a choline-deficient diet are associated with liver injury through inflammation and an increased aspartate aminotransferase (AST) level [91]. Finally, according to recent research, pentadecanoic acid has shown cytotoxic effects in the human breast carcinoma MCF-7 stem-like cell line. It has been found to be a novel JAK2/STAT3 signaling pathway inhibitor, which is also responsible for cell cycle arrest and apoptosis in the mentioned cell line. These findings suggest that pentadecanoic acid may have potential therapeutic benefits in treating breast cancer [92]. Lipids play a vital role in personal care products, providing functional and performance benefits to cosmetic formulations. The careful selection and use of different lipid types can optimize the efficacy and sustainability of cosmetic products. Oils with a high content of linoleic, \(\alpha\)-linolenic, and \(\gamma\)-linolenic acids are successfully used in cosmetics. They are classified as embilients, due to their moisturizing, softening, and smoothing properties. It has been confirmed that the lack of linoleic acid in the diet leads to skin abnormalities such as dryness and inflammation [93]. Such oils act as a base for creams, emulsions, cosmetic mills, etc., and may be treated as a solvent for many of the biologically active substances found in cosmetics, like vitamins A, D, and E or pigments [94; 95]. Unsaturated fatty acids are often crucial remedies in skincare and the treatment of dermatoses, such as atopic dermatitis (eczema). Linolenic acids both regenerate the damaged lipid barrier of the epidermis and limit water loss [96]. Maintaining the structure and function of the outer layer of skin, known as the stratum corneum, is strictly dependent on fatty acids. The lipids present in the intercellular matrix of the stratum corneum help to keep the layer cohesive, protect the skin from harmful substances, and prevent water loss. Therefore, the deficiency of fatty acids and lipids can significantly affect vascular fragility, weaken the immune system, and interfere with the blood clotting process [94]. Taking into account the source of triacylglycerlycerols, vegetable oils do not contain arachidonic acid (ARA), but fungi can easily produce it.