Whole-cell bacterial biosensors hold great promise as a practical complementary approach for in-field detection of arsenic. Although there are various bacterial bioreporter systems for arsenic detection, fewer studies reported the immobilization of arsenic bioreporters. This study aimed at determining immobilization of specific bacterial bioreporter in agar and alginate biopolymers to measure level of arsenite and/or arsenate. To achieve sensitive detection, immobilization parameters of polymer concentration and cell density were evaluated. Moreover, by changing the culture medium, immobilized bioreporter cells in minimal medium can detect arsenite while they can detect both arsenite and arsenate in phosphate-limited minimal medium. When optimal parameters were applied, agar and alginate immobilized bioreporter systems can detect arsenite and arsenate concentrations of 10 mu g/l and 200 mu g/l within 5 h and 2 h, respectively. The results showed that the immobilized bacterial bioreporter systems are able to determine the concentrations of the two abundant species of arsenic; arsenite and arsenate, as opposed to other studies which reported only arsenite detection. This is the first study describe agar hydrogel and alginate bead immobilization of fluorescent arsenic bacterial bioreporter that can detect both arsenite and arsenate at the safe drinking water limit. Thus, this study will enable further steps to be taken towards developing sensitive and selective portable devices to assess environmental arsenic contamination and prevent acute arsenic toxicity.