Biosurfactants are microbial-derived surface-active agents that can be used as emulsifiers, de — emulsifiers, wetting agents, foaming agents, functional food ingredients, and detergents in various industrial sectors such as petrochemicals, food and beverages, cosmetics and pharmaceuticals, agrochemicals, and fertilizers. They are preferred to chemical surfactants due to their biodegradability, surface properties, and low toxicity. Rhamnolipid is a type of biosurfactants synthesized by Pseudomonas aeruginosa. This microorganism produced 15.4 g/L of rhamnolipid during growth in a basal medium supplemented with crude glycerol (Zhang et al. 2005).

Another type of biosurfactant, called sophorolipid (SL), is produced by yeast Candida bombicola as an extracellular glycolipid. This glycolipid is composed of a disaccharide (i. e., sophorose) attached to a hydroxy fatty acyl moiety at the omega minus one or omega carbon atom (Asmer et al. 1988). The fatty acid (saturated or unsaturated) component of the glyco­lipid is composed of 16-18 carbons. The carboxyl group is either lactonized to the disac­charide ring or free as in the open chain form. Since the hydroxyl groups attached to the disaccharide ring are capable of being acetylated, the whole molecule is amphiphilic with surfactant properties. C. bombicola produced 9 g/L of SL in a pure glycerol medium, but when grown in glycerol waste stream obtained from a biodiesel plant, up to 60 g/L SLs was produced. This dramatic increase in SL production was attributed to low osmotic stress and presence of fatty acids in the crude glycerol (Ashby et al. 2005).

The conversion of glycerol to single cell oil (SCO) by microbes is another commercially important process due to the use of SCO as nutraceuticals, pharmaceuticals, and feed ingre­dients for aquaculture. Microbial lipids have similar properties to vegetable fats and oils in terms of structure and composition and hence have potential to replace them. Y. lipolytica, when grown in a medium containing crude glycerol, produced 8.1 g/L of SCO at the dilution rate of 0.03/h with a maximum productivity of 1.2 g/L/h (Papanikolaou et al. 2002).

Docosahexaenoic acid is an omega-3 polyunsaturated fatty acid (ю — 3 PUFA) that has a protective role against cancers, Alzheimer’s disease, cardiovascular diseases, schizophrenia, and so on. This compound is currently obtained from fish oil but can also be extracted from ю — 3 PUFA-enriched marine algae. The extracted PUFA can be used as a food additive, pharmaceutical, and aquaculture feed ingredient. The marine alga Schizochytrium limacinum produced large amounts of docosahexaenoic acid when grown on either a glucose or a glyc­erol medium. When crude glycerol was used as a carbon source, S. limacinum produced approximately 4.91 g/L docosahexaenoic acid (Chi et al. 2007).

Glycerol can be chemically converted to a variety of commercially important chemicals such as propylene glycol, propanediols, and acrolein. Traditionally, glycerol is esterified to fatty acids to produce polyglycerol esters that are used either as emulsifiers in the food indus­try or as detergents. The price of glycerol has fallen recently, and the production of other high-value chemicals from glycerol has been explored. These include the oxidation of glycerol to glyceric acid and tartronic acid, and the production of glycerol carbonate.