Tuberculosis (TB) is a worldwide major health problem which infects one third of the world’s population. The absence of reliable diagnostic tool in suburban area, where TB cases are most likely found, is still a great obstacle in TB eradication effort. Seeing Indonesia as one of the high burden countries for TB, UI-Indonesia iGEM team are trying to create a reliable, portable, and easy to use diagnostic tool for detecting TB. We are constructing a biosensor consist of highly specific antibody bound to a fragment of Beta-Galactosidase as a reporter to detect the presence of protein Ag85, a novel TB biomarker. Our goal is to make a biosensor that will detect the presence of antigen 85 in blood serum of TB suspect. Positive result will be indicated with easy to detect blue color, and when it’s negative, no response will be observed.