Bioprospecting of Microorganism-Based Industrial Molecules. Группа авторов

monoxide, sulfur dioxide, and nitrogen dioxide) and volatile organic compounds (VOCs) [42]. These pollutants upon skin absorption can induce direct oxidative damage to skin cells and extracellular matrix elements. Conversely, they may also display indirect toxic effects by stimulating the aryl hydrocarbon receptor (AhR) transduction pathway [43]. AhR is present in skin cells whose natural ligand is a xenobiotic compound dioxin. AhR activation induces the expression of cytochrome P450 enzymes, which are involved in xenobiotic compound degradation. Certain by‐products/intermediates of this pathway are toxic to the cell in the sense that they may generate oxidative stress [43]. AhR pathway can be activated by several VOCs and gaseous pollutants with variable efficacies. Recurrent exposer of skin to such air pollutants will accelerate the skin aging process.

      Overall, our skin needs to be carefully looked in before applying any cream, lotion, or ointment on the skin. Normally, creams are composed of either synthetic or natural ingredients. To date, due to high demand and consumption under the skincare segment, much of the creams are combinations of synthetic chemicals. However, drawbacks like side reactions, allergy are shifting the interest of the market on organic, herbal, or natural cosmetics. Also, to fulfil current market demand, most of the companies are working on finding a biological source for the production of important cosmetic compounds instead of going to generate new synthetic compounds. This trend will lead to the sustainable production of cosmetics using biological origin to satisfy the consumers' demand [44].

4.4 Why Microbes

The microbial products are of utmost importance because of their versatility, and there are multiple reasons behind it, viz., easy culturing, infinite production, the end product being eco‐friendly, and nontoxic [44]. When it comes to cosmetics, any product with applicable effectiveness remains in high demand and usage on one of the sensitive and environmentally exposed human organ skin, which is also of a socio and psychological concern for the human being that makes it even more effective. However, the skin is a multilayer organ consisting of differentiated cells playing different functions associated with defense, skin color, sensation, prevention of water loss, and structural integrity; therefore, it is crucial to have formulations that do not interfere with other structures and mechanisms. Pharmaceutical ingredients that are practiced currently in the market are being utilized beyond its capacity, and hence at multiple levels, it reveals certain side effects because of synthetic and chemical nature, while microbial products have got the advantage over it having nontoxic nature [45]. As we know, culturing microbes is conventional and easy on a large scale nowadays due to automated specifically designed fermenter machines, which keeps optimized conditions for the entire production cycle. Therefore, biological products have got the ease of adaptation to the human body and environment as they possess organic nature and comparatively fewer side effects. Another parameter associated with the benefit of using microbial products is they can be modified according to physicochemical requirements and optimized according to physicochemical needs, for example, usage of several enzymes into textile and detergent industries [45]. However, it can be applicable for enzymatic activities, but similar studies support the modification of microbial products and enhancements of physicochemical properties of active compounds under different conditions. For example, the production of keratinase enzyme by Bacillus subtilis and production of rhamnolipids by Pseudomonas aeruginosa where keratinase enzyme remains active molecule produced by microbes to utilize keratin from surrounding, and rhamnolipid remains secondary metabolite secreted to enhance surface activity to enhance adherence and proliferation/differentiation of skin cells [46, 47]. Cosmetics require multiple formulations for specific applications like powder, ointment, face wash, skin lightening, cleansing, hair removing, smoothening, moistening, etc., so suitable selection of microbial product and its effectiveness under chemical formulation is a crucial task to project future of the formulated product and its long‐lasting effectiveness.

      4.4.1 Bacterial Compounds

      Bacteria are known to produce diverse and novel compounds with antiaging and antioxidant properties. Bacterial cultures have some definite advantages over fungal cultures, like fast growth, short life cycle, ease of genetic manipulation, and broader range pH and temperature tolerance. These types of bacterial compounds are spread in different domains of biomolecules ranging from peptides, carbohydrate derivatives, organic acids, lipid and derivatives, amino acids and secondary metabolites, etc. The class and range of these commercial important biologically active compounds produced by bacteria include polysaccharides, oligosaccharides, exopolysaccharides (EPS), biosurfactants, proteins, peptides, vitamins, etc. Although the yield not only depends upon the type of product but also upon the kind of bacteria, its metabolic profile, nutritional source, and physiological conditions, advances in genetic engineering, fermentation technology, and advanced purification methodologies have helped in enhancing the bacterial product yields to a greater level.

      4.4.2 Polysaccharides and Oligosaccharides

      4.4.2.1 Hyaluronic Acid

Hyaluronic acid (HA) is a high‐molecular‐weight glycosaminoglycan heteropolysaccharide made of repeated disaccharide units of N‐acetyl‐D‐glucosamine (GlcNAc) and D‐glucuronic acid (GlcA) linked by B‐(1→3) and B‐(1→4) glycosidic bonds. Many reports have shown numerous commercial applications of HA and its salts in cosmetic products like makeup kits, moisturizers, lotions, sprays, lipsticks, etc. [48]. HA can be derived from several natural sources, yet HA derived from bacterial fermentation and rooster combs are only used in cosmetics. Its major role in cosmetic formulations is for skin‐conditioning agents and viscosity‐enhancing agents. This is due to its ability to its large water retention capacity that provides hydration to the skin. Antiaging creams are another product using a large amount of HA [49]. The anti‐wrinkle effect of HA has also been reported, which was due to effective moisturization and improved skin elasticity [50]. The emergence of HA as a dermal filler in recent years has swiftly replaced collagen in nonsurgical cosmetic procedures [49].

      HA is a major component of the dermal skin matrix present in every tissue and body fluid. As an effect of the aging process, there is a gradual decrease in the glycosaminoglycan HA content in the dermal layer resulting in skin dryness glycosaminoglycan (GAG) hyaluronic acid. Protection from ultraviolet radiation, tissue regeneration, and water retention properties of HA has been reported [51, 52].

      Cyclodextrins are a class of cyclic oligosaccharides that are made of glucose molecules linked with α‐(1→4) linkage to form a close ring structure. Cyclodextrins find large applications in cosmetic products [53]. Bacterial cyclodextrinase enzyme helps to obtain a cyclic form of dextrin. Production of cyclodextrins is reported in Brevibacillus brevis strain CD 162 and Mycobacterium terrae KNR 9 [54, 55]. Cyclodextrins obtained from bacterial enzymatic transformations find applications in skin‐cleaning products due to its potential to increase the solubility of substances that are secreted by the skin, including fats. The addition of cyclodextrin complex with tanning agent dihydroxyacetone helps to vanish the odor of later. In a similar case, glutathione used to reduce melanin pigmentation, skin whitening, and improved skin texture. But the odor of glutathione prevents its extensive use in cosmetic products. But if the glutathione is mixed with cyclodextrins, it prevents the bad odor of glutathione yet holding the same effect on the skin [56]. Cyclodextrin is used to decrease the rate of volatilization of esters, sustained release, and longevity of aroma in perfumes, deodorants, and room freshener products and detergents. Fine cyclodextrin powders are also used in talcum, diapers, sanitary pads, diaper pads, napkins, etc., to control the odor.

      4.4.2.2 Bacterial Cellulose

      Bacterial cellulose (BC) is a natural homopolysaccharide made of repeating with B‐(1→4) linkages [57]. Bacterial cellulose shares all the properties shown by plant cellulose. The plant cellulose complexes with other natural polymers like hemicellulose and lignin, but BC is produced and obtained in relatively pure form. BC can be from several groups of bacteria like Gluconacetobacter xylinus, Gluconacetobacter hansenii, Glucoacetobacter pasteurianus [58, 59]. BC is used to make biomembranes that can be used in medicine and cosmetics and to its high degree of hydration has enhanced its uses in moisturizing creams