BIOSURFACTANTS AND BIOPOLYMERS 457 the extraction processes do not generate harmful residues. Sustainable ingredient sourcing has become an important area of research, and more and more companies are shifting to agricultural and microbial sources for their raw materials (5–10). Most of the beauty and personal care products are emulsions, and cold emulsifi cation is a good alternative to the conventional emulsifi cation processes. This eliminates the separate heating and cooling phases, thus reducing energy requirements during the production phase of the product life cycle. This process also makes it easier to control the emulsion, resulting in reduced production time (11). With regard to the fi nal phase, companies are using recycled paper to make cardboard for packaging. Some are turning to biopolymers as sustainable alterna- tives for packaging (12). Another approach taken by companies involves long-lasting, reusable packaging which can be refi lled (13). Although it is important to incorporate sustainability in every aspect of an industry, ingredient sourcing has a signifi cant role in ensuring sustainability within the cosmetic industry. The key ingredients used in the beauty and personal care products include surfactants, polymers, and emulsifi ers, among others. The demand for green products and the dwindling resources has forced the cosmetic industry to explore various alternatives for convention- ally derived cosmetic ingredients. Among these, biopolymers and biosurfactants have gained a lot of traction as viable alternatives to the chemically synthesized polymers and surfactants because of their biocompatibility and biodegradability (14–17). Biosurfac- tants have numerous advantages in terms of low toxicity and their effectiveness over wide pH and temperature ranges (18). The notable fi lm-forming properties of biopolymers such as chitosan and carboxymethyl cellulose and the potential to be used as effective thickeners (19) make them suitable for applications in diverse industries such as beauty and personal care, food, packaging (20), and textile (21). This article presents a review on sustainability in formulation design specifi c to the cos- metic industry as well as the effect of the green alternatives on the rheological properties and performance parameters of the formulations. SUSTAINABLE SOURCING OF RAW MATERIALS The fi rst and foremost environmental responsibility of cosmetic corporations is raw mate- rial sourcing and its degree of sustainability. These responsibilities can be fulfi lled by switching to bioalternatives for surfactants and polymers and also by the utilization of by-products from industrial wastes. A good way to do this is to use biosurfactants instead of synthetic surfactants for cosmetic applications. To extend the value of sustainability, biosurfactants can be obtained, for example, from fat- or carbohydrate-rich effl uents pro- duced by food or agricultural industries (5). There have been several studies where olive oil mill effl uents, waste frying oils, animal fats, molasses, etc. are proven to be useful sub- strates for the production of glycolipid-producing microorganisms (6,7,22–24). There also exist similar studies in the case of biopolymer sourcing (8–10). Apart from being responsibly sourced, bio alternatives are also lower in toxicity and are biodegradable in nature (25–30). Because polymers and surfactants comprise a major portion of cosmetic and personal care formulations and often accumulate in the environment over time, it is important to study the aspect of their biodegradability. The following sections expand further on the aforementioned concept of sustainable raw material sourcing and biodegradability.
JOURNAL OF COSMETIC SCIENCE 458 BIOSURFACTANTS Surfactants are an integral part of cosmetic and personal care applications. So far, the in- dustry has primarily incorporated synthetic surfactants to serve the purposes of cleaning, wetting, dispersing, emulsifying, foaming, etc. This extensive use of synthetic surfactants, however, does not come without negative environmental consequences. A high concen- tration of synthetic surfactants has adverse effects on aquatic fl ora and fauna, leads to toxic accumulation in the human body, and depletes water quality when discharged (31,32). Biosurfactants have been subjected to toxicity tests against synthetic surfactants. One such study conducted by Kanga et al. (25) observed the solubilization of naphthalene from crude oil using glycolipids produced by the Rhodococcus species. This was compared with the synthetic surfactant Tween-80 or polyoxyethylene sorbitan monooleate. The study of toxicity per mass revealed that the glycolipid was 50% less toxic than the Tween-80 surfactant. The biosurfactant also exhibited a higher EC50 (effective concentrations at which 50% of the test organisms die) value which means that it poses a low toxicity to aquatic life. Another such study conducted by Kumano et al. (26) observed the toxicity and surface activity of sophorolipids (SL) from Starmerella bombicola. Marine life was exposed to differ- ent concentrations of SL, and its growth was observed. Even with 72 h of exposure to the highest concentration of SL, the growth inhibition remained less than 50%. This EC50 is higher than those reported on the growth inhibition of microalga by chemical surfactants (27). The EC50 of SL was signifi cantly higher than that of sodium dodecyl sulfate and linear alkylbenzene sulfonate, which proved SL to be of low toxicity. This highlights the necessity of transitioning to biological surfactants. A challenge faced here is the tedious and expensive process of obtaining these biosurfactants for complete commercial and large-scale utilization. The key to combating this issue is to promote biosynthetic meth- ods of propagation while minimizing waste and maximizing yield. This would involve the microbial action of various types of yeasts, bacteria, and fungi (30). Even though the degree of toxicity of biosurfactants is without question far lower than that of synthetic surfactants, Munstermann et al. (33) found that the toxicity levels of biosurfactants can also vary depending on the source, strain, and synthesis. However, synthetic surfactants are grouped according to their charge affi nity and biosur- factants, and, on the other hand, can be classifi ed according to raw material of sourcing, chemical constitution, and molecular weight. They are most often categorized according to their raw material of sourcing as follows—glycolipids, lipopeptides, fatty acids, phos- pholipids, neutral acids, and polymeric biosurfactants (34,35). Glycolipids and lipopep- tides are low molecular weight biosurfactants. Higher molecular weight structures can be more easily classifi ed as bioemulsifi ers rather than as biosurfactants, and examples of these are polymeric saccharides, lipoproteins, etc (36,37). GLYCOLIPIDS Glycolipids, a well-studied classifi cation of biosurfactants, are lipid molecules linked co- valently to carbohydrate molecules. Glycolipids are further classifi ed as rhamnolipids (RLs), SLs, and trehalose lipids based on their individual head group polarities (38). RLs, which are synthesized by the genus Pseudomonas (particularly the strain, Pseudomonas aeruginosa), contain a mono/di rhamnose head group(s) linked by β-glycosidic bonds to a fatty acid tail group with a hydroxy functional group present in the third position (39).
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