Cloning and Expression of araA gene coding for l-arabinose Isomerase from soil isolates and identified as a Shigella flexneri. Biochemical characterization of Sf-AI, its substrate specificity and kinetic efficiency. Bioconversion of d-Galactose to d-Tagatose. l-ribose synthesis by two step bioconversion using Shigella flexneril-arabinose isomerase along with d-lyxose/ribose isomerase in sequential manner.