Completion of Partial Pathways Giving New Products, Gluconic acid, Vitamin C, Herbicola, Corynebacterium

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	Completion of Partial Pathways Giving New Products - Natural strains of any organism may be imperfect from an applied perspective and can be improved by extension of native pathways. Some of the examples, include the following: (i) 2-keto-L-gulonic acid (2-KLG) is a precursor of ascorbic acid (vitamin c) and its synthesis involves two steps, first involving conversion of glucose to 2, 5-diketo-D gluconic acid (2, 5-DKG) in Erwinia herbicola, and second involving the conversion of 2, 5- DKG to 2-KLG in a species of Corynebacterium. It has been shown that by cloning and transfer of gene for 2,5-DKG reductase from Corynebacterium to Erwinia, glucose can be converted to 2-KLG in a single fermentation step,
(ii) A similar approach (as for 2-KLG) was used for the synthesis of 7-aminocephalosporanic acid (7ACA), which can be used as the precursor for several semi synthetic antibiotics in Acremonium chrysogenum. (iii) A glycoprotein like erythropoietin produced by chinese hamster ovary (CHO) cells can be subjected to post translational modification by the transfer of a gene for p-galactoside α 2, 6 sialyltransferase. This enzyme causes sialyl α, 2, 6-galactosyl linkage on surface glycoprotein and can convert erythropoietin into a kind more closely resembling human erythropoietin which is rich in these linkages. (iv)Human H blood group antigen could be produced in mouse cells due to transfection with human DNA.