Development of the biosensor using olfactory receptors as the sophisticated chemical sensing element consists of one of the promotive scientific research field. Olfactory receptors play an important role in the signal transduction of chemicals into the electrical cellular activities. Although the various applications of reconstituted olfactory receptors expressing in cell lines have been reported, these cell-based biosensors have not yet realized the ultra-performance of olfaction in chemical sensing. The elucidation and functional reconstruction of molecular mechanism of the components in olfactory mucus is required to progress the next generation sensing technology.

Chemical/physical technique has been used for the detection of a very small amount of odorants, but it has a problem that pursuing high sensitivity and selectivity causes upsizing and high costs. Therefore, in late years, the bio sensors which are based on the high sensitive and selective nature of olfactory systems of organisms attract attention. They includes bio-mimic and bio-inspired sensors. Here I introduce the bio-use sensor which employs animals themselves as sensors. Recently, it was reported nematode C. elegans can discriminate the smell of cancer with high accuracy. The cancer diagnosis technology using C. elegans scent detection (n-nose) is high accurate, low cost, noninvasive and easy, and can detect an early cancer. n-nose has the possibility to change a conventional cancer diagnosis system.

Bio-sniffers for gaseous chemicals (trimethylamine, methyl mercaptan, formaldehyde, ethanol, etc.) have been developed with metabolizing enzymes as chemical recognition protein. The sniff devices could monitor the concentration change of the gas-phase chemical with high selectivity because of enzyme specificity. Novel optical approach (Sniff-cam) allows to visualize the spatio-temporal concentration change of chemical vapor such as body odor, wine ethanol.

Olfaction is an important modality for animals to know the environment and to survive in the natural world. In a sensory organ, olfactory epithelium (OE), olfactory sensory neurons express genes for chemical sensors, termed odorant receptors. The mouse OE expresses more than 1000 different types of odorant receptor genes, leading to discrimination between various kinds of odorants. Thus, the OE is the largest organ with such chemical sensors in a living body. Interestingly, it is reported that the mouse can detect even CO₂ by its olfaction. In this review, we introduce the molecular mechanism underlying CO₂ sensing in the olfactory system with our recent findings, and discuss a possible application for the CO₂ biosensor.

Malodorous substances such as hydrogen sulfide (H₂S), methyl mercaptan (MM), trimethylamine (TMA), and low molecular weight fatty acids (LMFAs) are released from pig’s feces. A packed column was used to separate these substances from the feces by gas chromatography (GC). Furthermore, FPD was used to detect H₂S and MM, and FID was used to detect TMA and LMFAs. However, the peaks of these target substances were inclined to be overlapped by those of other substances present in the feces. This is because，the packed column has low peak-separating ability，and FPD and FID have low detector resolution. Analytical methods for the detection of malodorous substances using a capillary column and a MS detector that have high peak-separating ability and high detector resolution were developed to resolve the abovementioned problems. The cold-trap method with liquid argon was used to concentrate H₂S, MM, and TMA before GC/MS analysis. Acetone absorption of LMFAs followed by dehydration and concentration was performed before GC/MS analysis. The quantitative levels obtained for the abovementioned substances were considered to be below the standard limit for a pigsty. MM and TMA were detected in a model experiment conducted to vaporize malodorous substances from an untreated pig’s feces under a neutral pH condition, however, H₂S and LMFAs, which are acidic substances, were not detected. Furthermore, H₂S and LMFAs were detected when the pig’s feces was acidified with phosphoric acid. These results demonstrated that the methods used in this study are useful for the analysis and research of odorous substances.

It has been over 40 years since the enactment of the Offensive Odor Control Law. The regulation methods by measuring the offensive odor chemicals and the odor index with sensory method have been enforced so far. These concentration regulation methods have many advantages, but have some disadvantages, too. The present regulation methods are not always the best ones. Thus, it is highly important to examine new methods by management standards, structure standards and operation standards thoroughly.