High manufacturing costs and oral delivery are the constraints in clinical application of calcitonin. We selected surface-displayed Saccharomyces cerevisiae as a low-cost and safe carrier for oral delivery of salmon calcitonin (sCT). The sCT DNA fragment, optimized according to the codon preference of S. cerevisiae, was synthesized and cloned into the plasmid M-pYD1 to yield recombinant yAGA2-sCT, which was induced to express sCT by galactose for 0, 12, and 24 h. sCT expression was detected on the cell surface by indirect immunofluorescence and peaked at 12 h. About 65% recombinants expressed sCT on flow cytometry. The in vivo and in vitro activity of recombinant sCT was determined by detecting bioactivity of antiosteoclastic absorption on bone wafers and orally administering yAGA2-sCT to Wistar rats, respectively. For safety assessment of yAGA2-sCT, we observed abnormalities, morbidity, and mortality and determined body weight, serum chemistry parameters, hematological parameters, and organ weight. In vitro bioactivity of the recombinant sCT was similar to that of commercial sCT, Miacalcic; oral administration of 5 g/kg yAGA2-sCT induced a long-term hypocalcemic effect in Wistar rats and no adverse effects. This study demonstrates that yAGA2-sCT anchoring sCT protein on a S. cerevisiae surface has potential for low-cost and safe oral delivery of sCT. (C) 2010 American Institute of Chemical Engineers Biotechnol. Prog., 26: 968-974, 2010