Biocatalysis for the production of carbohydrate esters.

Carbohydrate fatty acid esters are nonionic biosurfactants, which can be synthesized from the esterification of mono- or oligosaccharides by enzymatic catalysis. These esters are increasingly used as important commodity chemicals, such as low calorific sweeteners and biosurfactants in food, pharmaceutical and cosmetic industries. Recently, some of the ester derivatives have shown their therapeutic potential with antitumor activity, plant growth inhibition and antibiotic activities, which became one of the 'hot' subjects for various biological processes. However, this potential has not been fully explored because the production of oligoesters (e.g. di-, tri- and tetra-) of sugars is a difficult problem in organic chemistry because of the abundance of hydroxyl groups in sugar molecules and the similar reactivity of most of them. Solvent engineering can be employed to improve the yields of sugar esters by using biocatalytic reactions. Protein engineering is useful in improving the catalytic efficiency, thermostability and pH stability of biocatalysts for enzymatic synthesis of sugar ester. The use of recombinant DNA technology to produce large quantities of enzymes in a heterologous host will lower the overall production cost. The cloning of key enzyme genes for the carbohydrate esters biosynthesis pathway and overexpressing these genes using strong promoters in either plants or microorganisms through metabolic engineering will be also discussed in this review.