{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T17:37:32Z","timestamp":1790357852567,"version":"4.1.0"},"reference-count":50,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2021,7,19]],"date-time":"2021-07-19T00:00:00Z","timestamp":1626652800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Methanol (MeOH) in exhaled breath has potential for non-invasive assessment of intestinal flora. In this study, we have developed a biochemical gas sensor (bio-sniffer) for MeOH in the gas phase using fluorometry and a cascade reaction with two enzymes, alcohol oxidase (AOD) and formaldehyde dehydrogenase (FALDH). In the cascade reaction, oxidation of MeOH was initially catalyzed by AOD to produce formaldehyde, and then this formaldehyde was successively oxidized via FALDH catalysis together with reduction of oxidized form of \u03b2-nicotinamide adenine dinucleotide (NAD+). As a result of the cascade reaction, reduced form of NAD (NADH) was produced, and MeOH vapor was measured by detecting autofluorescence of NADH. In the development of the MeOH bio-sniffer, three conditions were optimized: selecting a suitable FALDH for better discrimination of MeOH from ethanol in the cascade reaction; buffer pH that maximizes the cascade reaction; and materials and methods to prevent leaking of NAD+ solution from an AOD-FALDH membrane. The dynamic range of the constructed MeOH bio-sniffer was 0.32\u201320 ppm, which encompassed the MeOH concentration in exhaled breath of healthy people. The measurement of exhaled breath of a healthy subject showed a similar sensorgram to the standard MeOH vapor. These results suggest that the MeOH bio-sniffer exploiting the cascade reaction will become a powerful tool for the non-invasive intestinal flora testing.<\/jats:p>","DOI":"10.3390\/s21144897","type":"journal-article","created":{"date-parts":[[2021,7,19]],"date-time":"2021-07-19T04:55:40Z","timestamp":1626670540000},"page":"4897","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":20,"title":["Biochemical Methanol Gas Sensor (MeOH Bio-Sniffer) for Non-Invasive Assessment of Intestinal Flora from Breath Methanol"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1683-1496","authenticated-orcid":false,"given":"Koji","family":"Toma","sequence":"first","affiliation":[{"name":"Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-0062, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kanako","family":"Iwasaki","sequence":"additional","affiliation":[{"name":"Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Geng","family":"Zhang","sequence":"additional","affiliation":[{"name":"Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5608-8863","authenticated-orcid":false,"given":"Kenta","family":"Iitani","sequence":"additional","affiliation":[{"name":"Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-0062, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1555-1281","authenticated-orcid":false,"given":"Takahiro","family":"Arakawa","sequence":"additional","affiliation":[{"name":"Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-0062, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1603-6174","authenticated-orcid":false,"given":"Yasuhiko","family":"Iwasaki","sequence":"additional","affiliation":[{"name":"Faculty of Chemistry, Materials and Bioengineering, Kansai University, Osaka 564-8680, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kohji","family":"Mitsubayashi","sequence":"additional","affiliation":[{"name":"Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-0062, Japan"},{"name":"Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,7,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Larsen, N., Vogensen, F.K., Van Den Berg, F.W.J., Nielsen, D.S., Andreasen, A.S., Pedersen, B.K., Al-Soud, W.A., S\u00f8rensen, S.J., Hansen, L.H., and Jakobsen, M. (2010). Gut microbiota in human adults with type 2 diabetes differs from non-diabetic adults. PLoS ONE, 5.","DOI":"10.1371\/journal.pone.0009085"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/1471-2164-14-873","article-title":"Polysaccharides utilization in human gut bacterium Bacteroides thetaiotaomicron: Comparative genomics reconstruction of metabolic and regulatory networks","volume":"14","author":"Ravcheev","year":"2013","journal-title":"BMC Genom."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"837","DOI":"10.1016\/j.cell.2006.02.017","article-title":"Ecological and Evolutionary Forces Shaping Microbial Diversity in the Human Intestine","volume":"124","author":"Ley","year":"2006","journal-title":"Cell"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1146\/annurev.mi.31.100177.000543","article-title":"Microbial Ecology of the Gastrointestinal Tract","volume":"31","author":"Savage","year":"1977","journal-title":"Annu. Rev. Microbiol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"6578","DOI":"10.1073\/pnas.95.12.6578","article-title":"Prokaryotes: The unseen majority","volume":"95","author":"Whitman","year":"1998","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Sekirov, I., Russell, S.L., Antunes, L.C.M., and Finlay, B.B. (2016). Gut Microbiota in Health and Disease Gut Microbiota in Health and Disease. Physiol. Rev., 859\u2013904.","DOI":"10.1152\/physrev.00045.2009"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"269","DOI":"10.1038\/ni888","article-title":"Angiogenins: A new class of microbicidal proteins involved in innate immunity","volume":"4","author":"Hooper","year":"2003","journal-title":"Nat. Immunol."},{"key":"ref_8","first-page":"14","article-title":"The influence of gut microbiota on drug metabolism and toxicity","volume":"110","author":"Achilefu","year":"2017","journal-title":"Expert Opin. Drug Metab. Toxicol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1027","DOI":"10.1038\/nature05414","article-title":"An obesity-associated gut microbiome with increased capacity for energy harvest","volume":"444","author":"Turnbaugh","year":"2006","journal-title":"Nature"},{"key":"ref_10","first-page":"417","article-title":"Cultivation of anaerobic intestinal bacteria","volume":"94","author":"Drasar","year":"1967","journal-title":"Pathology"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"596","DOI":"10.1128\/am.17.4.596-602.1969","article-title":"Fecal Microflora in Healthy Persons in a Preindustrial Region","volume":"17","author":"Mata","year":"1969","journal-title":"Appl. Microbiol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"799","DOI":"10.5604\/12321966.1129936","article-title":"Methods of analysis of gut microorganism\u2014Actual state of knowledge","volume":"21","author":"Szachta","year":"2014","journal-title":"Ann. Agric. Environ. Med."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1915","DOI":"10.1126\/science.1104816","article-title":"Host-bacterial mutualism in the human intestine","volume":"307","author":"Ley","year":"2005","journal-title":"Science"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Abubucker, S., Segata, N., Goll, J., Schubert, A.M., Izard, J., Cantarel, B.L., Rodriguez-Mueller, B., Zucker, J., Thiagarajan, M., and Henrissat, B. (2012). Metabolic reconstruction for metagenomic data and its application to the human microbiome. PLoS Comput. Biol., 8.","DOI":"10.1371\/journal.pcbi.1002358"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"603","DOI":"10.1152\/physrev.00034.2014","article-title":"Metabolic Methanol: Molecular Pathways and Physiological Roles","volume":"95","author":"Dorokhov","year":"2015","journal-title":"Physiol. Rev."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Martens, E.C., Lowe, E.C., Chiang, H., Pudlo, N.A., Wu, M., McNulty, N.P., Abbott, D.W., Henrissat, B., Gilbert, H.J., and Bolam, D.N. (2011). Recognition and degradation of plant cell wall polysaccharides by two human gut symbionts. PLoS Biol., 9.","DOI":"10.1371\/journal.pbio.1001221"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"848","DOI":"10.1093\/ajcn\/47.5.848","article-title":"Methanol production from the degradation of pectin by human colonic bacteria","volume":"47","author":"Siragusa","year":"1988","journal-title":"Am. J. Clin. Nutr."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"26","DOI":"10.1093\/jat\/25.1.26","article-title":"FT-IR breath test in the diagnosis and control of treatment of methanol intoxications","volume":"25","author":"Laakso","year":"2001","journal-title":"J. Anal. Toxicol."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Dorokhov, Y.L., Komarova, T.V., Petrunia, I.V., Kosorukov, V.S., Zinovkin, R.A., Shindyapina, A.V., Frolova, O.Y., and Gleba, Y.Y. (2012). Methanol may function as a Cross-Kingdom signal. PLoS ONE, 7.","DOI":"10.1371\/journal.pone.0036122"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"939","DOI":"10.1111\/j.1530-0277.1997.tb03862.x","article-title":"Endogenous production of methanol after the consumption of fruit","volume":"21","author":"Lindinger","year":"1997","journal-title":"Alcohol. Clin. Exp. Res."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"639","DOI":"10.1126\/science.141.3581.639","article-title":"Methanol in normal human breath","volume":"141","author":"Eriksen","year":"1963","journal-title":"Science"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"637","DOI":"10.1088\/0967-3334\/27\/7\/007","article-title":"A longitudinal study of methanol in the exhaled breath of 30 healthy volunteers using selected ion flow tube mass spectrometry, SIFT-MS","volume":"27","author":"Turner","year":"2006","journal-title":"Physiol. Meas."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"047104","DOI":"10.1088\/1752-7155\/9\/4\/047104","article-title":"Increase of methanol in exhaled breath quantified by SIFT-MS following aspartame ingestion","volume":"9","author":"Dryahina","year":"2015","journal-title":"J. Breath Res."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"He, C., Liu, L., Korposh, S., Correia, R., and Morgan, S.P. (2021). Volatile Organic Compound Vapour Measurements Using a Localised Surface Plasmon Resonance Optical Fibre Sensor Decorated with a Metal-Organic Framework. Sensors, 21.","DOI":"10.3390\/s21041420"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Kittle, J., Fisher, B., Kunselman, C., Morey, A., and Abel, A. (2019). Vapor Selectivity of a Natural Photonic Crystal to Binary and Tertiary Mixtures Containing Chemical Warfare Agent Simulants. Sensors, 20.","DOI":"10.3390\/s20010157"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Furuuchi, N., Shrestha, R., Yamashita, Y., Hirao, T., Ariga, K., and Shrestha, L. (2019). Self-Assembled Fullerene Crystals as Excellent Aromatic Vapor Sensors. Sensors, 19.","DOI":"10.3390\/s19020267"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Slobodian, P., Riha, P., Olejnik, R., Matyas, J., and Slobodian, R. (2021). Microstrip Resonant Sensor for Differentiation of Components in Vapor Mixtures. Sensors, 21.","DOI":"10.3390\/s21010298"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Blank, A., Guendelman, G., and Linzon, Y. (2020). Vapor Sensing with Polymer Coated Straight Optical Fiber Microtapers Based on Index Sensitive Interference Spectroscopy of Surface Stress Birefringence. Sensors, 20.","DOI":"10.3390\/s20092675"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Angulo Barrios, C. (2019). Scotch Tape Optical Vapor Sensor for Ethanol\u2013Methanol Mixtures. Sensors, 19.","DOI":"10.3390\/s19245381"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"83870","DOI":"10.1039\/C6RA16636A","article-title":"Enhanced methanol sensing properties of SnO2 microspheres in a composite with Pt nanoparticles","volume":"6","author":"Li","year":"2016","journal-title":"RSC Adv."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Chen, Y., Dong, Z., Xue, X., Chen, S., Natan, A., Lv, Y., Chen, C., Yang, Y.Y., Cen, W., and Yang, Y.Y. (2020). High-sensitivity and high-selectivity detection of methanol based on La-doped SnO2 sensor. Appl. Phys. A Mater. Sci. Process., 126.","DOI":"10.1007\/s00339-020-03478-6"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"4155","DOI":"10.1021\/acsami.9b20763","article-title":"Methanol and Humidity Capacitive Sensors Based on Thin Films of MOF Nanoparticles","volume":"12","author":"Vijjapu","year":"2020","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_33","first-page":"1","article-title":"Highly selective detection of methanol over ethanol by a handheld gas sensor","volume":"10","author":"Abegg","year":"2019","journal-title":"Nat. Commun."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"102050","DOI":"10.1016\/j.isci.2021.102050","article-title":"Detecting methanol in hand sanitizers","volume":"24","author":"Magro","year":"2021","journal-title":"iScience"},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Hayasaka, T., Lin, A., Copa, V.C., Lopez, L.P., Loberternos, R.A., Ballesteros, L.I.M., Kubota, Y., Liu, Y., Salvador, A.A., and Lin, L. (2020). An electronic nose using a single graphene FET and machine learning for water, methanol, and ethanol. Microsyst. Nanoeng., 6.","DOI":"10.1038\/s41378-020-0161-3"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"113136","DOI":"10.1016\/j.bios.2021.113136","article-title":"Sensitive and selective methanol biosensor using two-enzyme cascade reaction and fluorometry for non-invasive assessment of intestinal bacteria activity","volume":"181","author":"Toma","year":"2021","journal-title":"Biosens. Bioelectron."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"127371","DOI":"10.1016\/j.snb.2019.127371","article-title":"Measurement of temperature and relative humidity in exhaled breath","volume":"304","author":"Mansour","year":"2020","journal-title":"Sens. Actuators B Chem."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"341","DOI":"10.1016\/j.bios.2016.12.050","article-title":"Bio-sniffer (gas-phase biosensor) with secondary alcohol dehydrogenase (S-ADH) for determination of isopropanol in exhaled air as a potential volatile biomarker","volume":"91","author":"Chien","year":"2017","journal-title":"Biosens. Bioelectron."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1021\/acssensors.7b00865","article-title":"Fiber-Optic Bio-sniffer (Biochemical Gas Sensor) Using Reverse Reaction of Alcohol Dehydrogenase for Exhaled Acetaldehyde","volume":"3","author":"Iitani","year":"2018","journal-title":"ACS Sens."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"12261","DOI":"10.1021\/acs.analchem.7b03191","article-title":"Biochemical Gas Sensors (Biosniffers) Using Forward and Reverse Reactions of Secondary Alcohol Dehydrogenase for Breath Isopropanol and Acetone as Potential Volatile Biomarkers of Diabetes Mellitus","volume":"89","author":"Chien","year":"2017","journal-title":"Anal. Chem."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"10415","DOI":"10.1038\/s41598-021-90146-1","article-title":"External ears for non-invasive and stable monitoring of volatile organic compounds in human blood","volume":"11","author":"Toma","year":"2021","journal-title":"Sci. Rep."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1269","DOI":"10.1007\/s00216-007-1824-8","article-title":"Glucose sensor using a phospholipid polymer-based enzyme immobilization method","volume":"391","author":"Kudo","year":"2008","journal-title":"Anal. Bioanal. Chem."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"129260","DOI":"10.1016\/j.snb.2020.129260","article-title":"Dual-target gas-phase biosensor (bio-sniffer) for assessment of lipid metabolism from breath acetone and isopropanol","volume":"329","author":"Toma","year":"2021","journal-title":"Sens. Actuators B Chem."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"245","DOI":"10.1016\/j.bios.2018.09.070","article-title":"Real-time monitoring of skin ethanol gas by a high-sensitivity gas phase biosensor (bio-sniffer) for the non-invasive evaluation of volatile blood compounds","volume":"129","author":"Arakawa","year":"2019","journal-title":"Biosens. Bioelectron."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"2142","DOI":"10.1111\/1462-2920.14130","article-title":"Genome-based evolutionary history of Pseudomonas spp.","volume":"20","author":"Hesse","year":"2018","journal-title":"Environ. Microbiol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"2844","DOI":"10.1002\/rcm.3685","article-title":"Selected ion flow tube mass spectrometry of exhaled breath condensate headspace","volume":"22","author":"Dryahina","year":"2008","journal-title":"Rapid Commun. Mass Spectrom."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"3939","DOI":"10.1021\/acssensors.0c01589","article-title":"Ultrafast Detection and Discrimination of Methanol Gas Using a Polyindole-Embedded Substrate Integrated Waveguide Microwave Sensor","volume":"5","author":"Kumar","year":"2020","journal-title":"ACS Sens."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"4746","DOI":"10.1021\/acsanm.8b00965","article-title":"Improved Methanol Detection Using Carbon Nanotube-Coated Carbon Fibers Integrated with a Split-Ring Resonator-Based Microwave Sensor","volume":"1","author":"Singh","year":"2018","journal-title":"ACS Appl. Nano Mater."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"488","DOI":"10.1016\/j.snb.2015.04.083","article-title":"Enhanced methanol gas-sensing performance of Ce-doped In2O3 porous nanospheres prepared by hydrothermal method","volume":"216","author":"Han","year":"2015","journal-title":"Sens. Actuators B Chem."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"127713","DOI":"10.1016\/j.snb.2020.127713","article-title":"Platinum decorated mesoporous titanium nitride for fuel-cell type methanol gas sensor","volume":"308","author":"Meng","year":"2020","journal-title":"Sens. Actuators B Chem."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/14\/4897\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:31:38Z","timestamp":1760164298000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/14\/4897"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,7,19]]},"references-count":50,"journal-issue":{"issue":"14","published-online":{"date-parts":[[2021,7]]}},"alternative-id":["s21144897"],"URL":"https:\/\/doi.org\/10.3390\/s21144897","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,7,19]]}}}