2.4.1.276 synthesis biosynthesis of zeaxanthin diglucoside is obtained when the gene crtX is co-transformed into Escherichia coli containing the plasmids carrying crtE, crtB, crtI, crtY, and crtZ genes required for zeaxanthin beta-D-diglucoside biosynthesis 2.4.1.276 synthesis production of rare beta-carotene-modified carotenoids possessing 2-O, 2-H or 2-glucosyl and/or 3-O, 3-H or 3-glucosyl functionalities in their beta-ionone rings using a recombinant Escherichia coli approach, involving expression of carotenoid biosynthesis genes crtE, crtB, crtI, crtY, crtZ, crtX and crtG. From the cells of the recombinant Escherichia coli, caloxanthin i.e. (beta,beta-carotene-2,3,2',3'-tetrol)-3'-beta-D-glucose, zeaxanthin i.e. (beta,beta-carotene-3,3'-diol) 3,3'-beta-D-diglucoside, and nostoxanthin i.e. (beta,beta-carotene-2,3,3'-triol) are isolated and identified. Caloxanthin 3'-beta-D-glucoside displays potent 1O2 quenching activity 2.4.1.276 synthesis Escherichia coli cells that express the full six carotenoid biosynthesis genes (crtE, crtB, crtI, crtY, crtZ, and crtX) of the bacterium Pantoea ananatis synthesizes zeaxanthin 3,3'-beta-D-diglucoside and 3-beta-glucosyl-3'-beta-quinovosyl zeaxanthin. The singlet oxygen-quenching activity of zeaxanthin 3,3'-beta-D-diglucoside is superior to that of zeaxanthin 2.4.1.276 synthesis Escherichia coli strain CAR001 carries the crtEXYIB operon of Enterobacter agglomerans to produce beta-carotene. Deletion of genes encoding zeaxanthin glucosyltransferase (crtX) and lycopene beta-cyclase (crtY) from the operon leads to production of 10.5 mg lycopene/l. Further optimization results in a strain producing 3.52 g lycopene/l in fed-batch fermentation