BIOSURFACTANTS AND BIOPOLYMERS 467 increasing the extraction yield (112). Other extraction approaches that are being explored include subcritical water extraction and ultrasound-assisted extraction, both of which optimize the process of pectin isolation from plant material (111,113,114). XANTHAN GUM Xanthan gum is a branched polysaccharide where the repeating units are composed of penta- saccharide units that include two glucose units, two mannose units, and one glucuronic acid unit (Figure 10). It is primarily produced by the bacterial fermentation of a plant pathogenic bacterium Xanthomonas campestris (115). Polysaccharides such as xanthan which are obtained from bacterial sources are promising alternatives to plant-based polysaccharides. Commerci al xanthan is obtained by batch fermentation and thermal treatment followed by recovery of the product using alcohol. The effi ciency of the production process and the quality of the fi nal product are heavily dependent on various process conditions like the microorganism used as well as the nutrients such as carbon and nitrogen supplied for cul- ture growth. Because the production solely depends on glucose or saccharose as the main carbon source, it is quite expensive (116). There are many studies that explore alternative sources of carbon that can help in reducing the production costs of this biopolymer (117–119). Several food- and agro-based industries generate large amounts of agricultural waste. If not discarded properly, they can harm the soil and water bodies. Numerous studies have suggested the potential use of these wastes as a carbon and nitrogen source for various biotech processes. Woiciechowski et al. (117) showed that residues like cassava bagasse can be hydrolyzed and used as a carbon source for xanthan production with high yields. CARBOXYM ETHYL CELLULOSE Carboxym ethyl cellulose is a natural polymer derived from cellulose. Plant cell walls are the primary source of cellulose. It is made up of monomeric units of anhydroglucose Figure 10. Chemica l structure of xanthan gum.

JOURNAL OF COSMETIC SCIENCE 468 where the glucose units are bound through β-1,4-glycosidic bonds (Figure 11). The var- ied chemical properties of this polysaccharide are attributed to the three reactive hydroxyl groups present in cellulose (120, 121). When cellulose is treated with an alkali and the hydroxyl groups are made to react with carboxymethyl in the presence of an organic solvent like sodium monochloroacetate, an ether is formed. This etherifi cation reaction leads to the formation of carboxymethyl cellulose (120). Cellulose is primarily extracted from agricultural or domestic wastes. A signifi cant amount of waste is generated from agricultural industries and practices across the world (120–122). These residues are usually burnt, resulting in adverse environmental and other health issues (121). Huang et al. (121) explored the possibility of effective utilization of these agricultural by-products to produce cellulose and fi nally carboymethyl cellulose. They synthesized and characterized carboymethyl cellulose from various agro-wastes such as sugarcane bagasse and spent tea leaves obtained from different agro-based industries. They found that the physicochemical properties of carboymethyl cellulose produced from these residues were comparable to those of commercial carboymethyl cellulose. BIODEGRAD ABILITY A large n umber of “rinse off” cosmetic and personal care products such as shampoos, condi- tioners, soap, and toothpaste make use of polymers as fi lm formers, viscosity modifi ers, and stabilizers. These polymers are sometimes present in the form of microplastics. Microplas- tics are synthetic, nondegradable polymers with a size less than 5 mm (123). These poly- mers along with several other synthetic ingredients often end up in wastewater streams. Extensive studies have shown that wastewater treatment plants do not successfully remove these synthetic ingredients, and instead, a portion of the microplastics is emitted to water bodies (124,125). Oftentimes, sludge from treatment plants are used as fertilizers for crops. Microplastics also tend to accumulate in the sludge during the treatment process and thus start building up in the environment as well as at higher levels of the food chain (125). Whereas b iopolymers are completely biodegradable, the rate of degradation can range from a few hours to years according to the functional group present. Biopolymers usually Figure 11. Ch e mical structure of carboxymethyl cellulose.