Flavorings and additives
The worldwide market for food additives and supplements is worth tens of billions of dollars yearly and demand grows annually by 4%. The complex organic compounds that make up food flavors can be made using synthetic organic chemical approaches, but are made more cheaply as microbial products or as a result of microbial bioconversions. Flavors as a whole are a diverse group of compounds including aldehydes, esters, lactones, polyols, and terpenes and a range of microorganisms are used to produce them. Food regulations in the US and Europe allow the classification of flavors (and many other products) as ‘natural’ even if they are produced by bulk fermentation of a Bacterial or fungal culture. For example, citronellol produced by Kluyveromyces lactis can be used as a natural flavoring in fruit drinks.
Flavors are often targeted by biotechnologists as the equivalents in unprocessed foods are expensive or difficult to isolate from plant material. For example, cocoa butter from cocoa beans is high in value and is prone to developing off flavors during storage or processing as the fats within it become rancid. Tea seed oil is a byproduct of tea processing and can be converted by a microbial or fungal inter-esterase into a fatty acid strongly resembling true cocoa butter. The reaction uses 1, 3-dipalmitoyl-2-oleyl glycerol mixed with stearic acid, and this becomes 1, 3-distearoyl-2-oleyl glycerol (the product) and palmitic acid after inter-esterase treatment.
Some of the biggest value microbial products include the nucleosides. Guanosine triphosphate is a base used in the synthesis of RNA but can be overproduced by strains of Bacillus subtilis. It is added to food to give the ‘umami’ taste. It is often used in com- bination with another product of Bacillus, disodium inosinate, to enhance the flavor of instant noodles, cured meats, tinned vegetables, and dried soups.
Food additives now include the ‘neutraceuticals,’ compounds that are believed to be important for nutrition but are not classified as drugs in most countries. Ascorbic acid (vitamin C, produced from Acetobacter suboxydans), cyanocobalamin (vitamin B12, produced from a number of bacteria including Pseudomonas denitrificans and Streptomyces griseus), and riboflavin (vitamin B2, produced from recombinant Bacillus subtilis) are added to many foods, including cereals, or are sold as vitamin supplement pills.