Biosensors and Bioelectronics 21 (2005) 67–73 Development of photocatalytic biosensor for the evaluation of biochemical oxygen demand Gab-Joo Chee a,∗ , Yoko Nomura a,b , Kazunori Ikebukuro a,c , Isao Karube a,b a ResearchCenterforAdvancedScienceandTechnology,TheUniversityofTokyo,4-6-1KomabaMeguro-ku,Tokyo153-8904,Japan b SchoolofBionics,TokyoUniversityofTechnology,1404KatakuraHachioji,Tokyo192-8580,Japan c DepartmentofBiotechnologyandLifeScience,FacultyofEngineering,TokyoUniversityofAgricultureandTechnology, 2-24-16NakaKoganei,Tokyo184-8588,Japan Received 18 May 2004; received in revised form 7 October 2004; accepted 7 October 2004 Abstract The photocatalytic biosensor of flow system using semiconductor TiO 2 was developed to evaluate biochemical oxygen demand (BOD) levels in river water. Photocatalysis of sample was carried out in a photoreactor with TiO 2 and a 6 W black-light blue fluorescent tube as light source. Sample from a photoreactor outlet was measured by an oxygen electrode with a biofilm. The sensor response of photocatalytic biosensor was between 5 and 10 min depending on concentration of biochemical in the samples. At BOD of 1 mg l -1 , the sensor response increased 1.33-fold in comparison with that without photocatalysis. The degradation of tannic acid and humic acid with photocatalysis were 51.8 and 38.4%, respectively. Gum arabic and linear alkylbenzene sulfonate (LAS) were degraded a little, but gave the responses of more than double to the sensor. Free radicals yielded by photocatalysis in a photoreactor did not affect the sensor response because their lifetime is extremely short. Fairly good correlation (r = 0.983) between the sensor method and the conventional method was obtained for test samples. This biosensor using photocatalytic pretreatment improved the sensitivity. © 2004 Elsevier B.V. All rights reserved. Keywords: Photocatalysis; TiO 2 ; BOD sensor; Biosensor; Biofilm; Pseudomonasputida; Artificial wastewater 1. Introduction Many countries have enforced many policies for the en- vironmental protection and the environmental conservation, nevertheless environmental pollution become gradually serious. Particularly, rivers, the major drinking water sources are getting polluted. Biochemical oxygen demand (BOD) was one of the most typical methods determining pollutants in river. Since BOD sensor is first reported in 1977 (Karube et al., 1977), many research groups have developed BOD sen- sors that use various microorganisms and devices involving ∗ Corresponding author. Present address: Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology, 2-15 Nat- sushima, Yokosuka 237-0061, Japan. Tel.: +81 46 867 9651; fax: +81 46 867 9645. E-mailaddress: cheegj@jamstec.go.jp (G.-J. Chee). mediators (Morris et al., 2001; Liu and Mattiasson, 2002). In the present, the BOD 5 method is adopted (APHA, 1986), and this test method takes 5 days until results are obtained. Therefore our laboratory has developed a biosensor for the determination of BOD in river water (Chee et al., 1999, 2000). A standard solution used for this biosensor was artifi- cial wastewater (AWW) instead of solution containing equal mass concentration of glucose and glutamic acid (GGA). AWW generally consisted of humic acid, lignin, tannic acid, gum arabic and LAS, which were recalcitrant organic compounds in river water (Murakami et al., 1978; Tanaka et al., 1994). This biosensor, however, often showed low values compared with the conventional BOD 5 in the evaluation of river waters. The results would show that recalcitrant organic compounds in river are uneasily assimilable to the immobilized microorganism in such a short measuring times. 0956-5663/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2004.10.005