for determination of organic compounds in foods, electrochemical monitoring devices (biosensors) employing immobilized biocatalysts such as immobilized enzymes, organelles, microorganisms and tissue have definite advantages. enzyme sensors could be used for the determination of sugars, amino acids, organic acids, alcohols, lipids, nucleic acid derivatives, etc. a multifunctional biosensor for the determination of several compounds has been developed for food processing. on the other hand, immobilized microorganisms and electrodes have been used for industrial and environmental analysis. microbial sensors were applied for the determination of sugars, organic acids, alcohols, amino acids, mutagens, methane, ammonia, and bod. micro-biosensors using immobilized biocatalysts and ion sensitive field effect transistor or microelectrodes prepared by silicon fabrication technologies have been developed for medical application and food processing. this review summarizes the design and application of biosensors