[ABSTRAK
Elektroda AuNp-BDD dan Au-BDD dikembangkan sebagai elektrodakerja untuk pengukuran biochemical oxygen demand (BOD) menggunakanRhodotorula mucilaginosa UICC Y-181 terimobilisasi pada Na-alginat.Pengukuran BOD dilakukan dengan mengamati perubahan konsentrasi oksigenakibat proses oksidasi senyawa organik dalam larutan oleh mikroorganisme.Glukosa dan galaktosa digunakan sebagai model senyawa organik. Teknik multipulse amperometry pada potensial reduksi oksigen -670 mV vs Ag/AgCldigunakan untuk mendeteksi oksigen sisa yang tidak digunakan olehmikroorganisme. Waktu tunggu optimum adalah 10 menit dan ketebalan lapisanimobilisasi adalah 2 mm. Karakterisasi elektroda dengan XPS menunjukkan rasioAu/C untuk Au-BDD dan AuNp-BDD adalah 0.0553 dan 0.2084. Padapengukuran oksigen, elektroda AuNp-BDD ditemukan lebih sensitif dibandingkanelektroda Au-BDD maupun elektroda Au. Sedangkan sensor BOD denganmikroorganisme terimobilisasi ditemukan memiliki waktu pengukuran lebih cepat,sensitifitas lebih tinggi, repeatbility lebih baik dan limit deteksi lebih rendahdibandingkan sensor dengan mikroorganisme bebas. Kelinieran yang baik (R2 =0.994) ditunjukkan untuk glukosa pada retang konsentrasi 0.1 ? 0.9 mM(ekuivalen dengan 10 ? 90 mg/L BOD) dan limit deteksi 0.46 mg/L BOD.Kestabilan arus yang baik ditunjukkan oleh nilai RSD 3.35% (n=8 pengukuran).Laju konsumsi oksigen dengan sumber karbon glukosa lebih tinggi dari galaktosamenandakan bahwa khamir Rhodotorula mucilaginosa lebih mudah mendegradasiglukosa. Keberadaan ion Cu2+ memberikan pengaruh pada sel khamirRhodotorula mucilaginosa dengan penurunan konsumsi oksigen.

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ABSTRACT
NanoGold-modified boron doped diamond (AuNp-BDD) and Golddepositedboron doped diamond (Au-BDD) electrodes were used as workingelectrodes for measuring biochemical oxygen demand (BOD) using Rhodotorulamucilaginosa UICC Y-181 immobilized in a Na-alginate matrix. BODmeasurement is done by observing the changes in oxygen concentration due tooxidation of organic compounds in solution by microorganisms. Glucose andgalactose were used as model organic compounds. Multy-pulse amperometrytechnic at -0.67 V (vs Ag/AgCl) of oxygen reduction potensial was used to detectthe remaining of oxygen which is not used by microorganisms. An optimumwaiting time was observed to be 10 min and thickness of immobilization matrix is2 mm. Ratio of Au/C 0.0553 and 0.2084 was obtained by XPS for Au-BDD andAuNp-BDD electrodes, respectively. Dissolved oxygen detection, AuNp-BDDelectrode is more sensitive than Au-BDD or Au electrodes. The BOD sensor usingimmobilized microorganism was found to have a faster measurement time, highersensitivity, better repeatbility and lower detection limit compared to the sensorusing free microorganisms. Good linierity (R2 = 0.994) was shown in the range ofglucose concentration of 0.1 ? 0.9 mM (equivalent to 10 ? 90 mg/L BOD) anddetection limit of 0.46 mg/L BOD. Good stability of currents were shown by anRSD of 3.35%(n=8). The rate of oxygen consumption to glucose is higher than ofgalactose, indicating that glucose is a better substrate for Rhodotorulamucilaginosa than that of galactose. The presence of Cu ions influence the yeastcells with a decreasing in oxygen consumption.;NanoGold-modified boron doped diamond (AuNp-BDD) and Golddepositedboron doped diamond (Au-BDD) electrodes were used as workingelectrodes for measuring biochemical oxygen demand (BOD) using Rhodotorulamucilaginosa UICC Y-181 immobilized in a Na-alginate matrix. BODmeasurement is done by observing the changes in oxygen concentration due tooxidation of organic compounds in solution by microorganisms. Glucose andgalactose were used as model organic compounds. Multy-pulse amperometrytechnic at -0.67 V (vs Ag/AgCl) of oxygen reduction potensial was used to detectthe remaining of oxygen which is not used by microorganisms. An optimumwaiting time was observed to be 10 min and thickness of immobilization matrix is2 mm. Ratio of Au/C 0.0553 and 0.2084 was obtained by XPS for Au-BDD andAuNp-BDD electrodes, respectively. Dissolved oxygen detection, AuNp-BDDelectrode is more sensitive than Au-BDD or Au electrodes. The BOD sensor usingimmobilized microorganism was found to have a faster measurement time, highersensitivity, better repeatbility and lower detection limit compared to the sensorusing free microorganisms. Good linierity (R2 = 0.994) was shown in the range ofglucose concentration of 0.1 ? 0.9 mM (equivalent to 10 ? 90 mg/L BOD) anddetection limit of 0.46 mg/L BOD. Good stability of currents were shown by anRSD of 3.35%(n=8). The rate of oxygen consumption to glucose is higher than ofgalactose, indicating that glucose is a better substrate for Rhodotorulamucilaginosa than that of galactose. The presence of Cu ions influence the yeastcells with a decreasing in oxygen consumption., NanoGold-modified boron doped diamond (AuNp-BDD) and Golddepositedboron doped diamond (Au-BDD) electrodes were used as workingelectrodes for measuring biochemical oxygen demand (BOD) using Rhodotorulamucilaginosa UICC Y-181 immobilized in a Na-alginate matrix. BODmeasurement is done by observing the changes in oxygen concentration due tooxidation of organic compounds in solution by microorganisms. Glucose andgalactose were used as model organic compounds. Multy-pulse amperometrytechnic at -0.67 V (vs Ag/AgCl) of oxygen reduction potensial was used to detectthe remaining of oxygen which is not used by microorganisms. An optimumwaiting time was observed to be 10 min and thickness of immobilization matrix is2 mm. Ratio of Au/C 0.0553 and 0.2084 was obtained by XPS for Au-BDD andAuNp-BDD electrodes, respectively. Dissolved oxygen detection, AuNp-BDDelectrode is more sensitive than Au-BDD or Au electrodes. The BOD sensor usingimmobilized microorganism was found to have a faster measurement time, highersensitivity, better repeatbility and lower detection limit compared to the sensorusing free microorganisms. Good linierity (R2 = 0.994) was shown in the range ofglucose concentration of 0.1 ? 0.9 mM (equivalent to 10 ? 90 mg/L BOD) anddetection limit of 0.46 mg/L BOD. Good stability of currents were shown by anRSD of 3.35%(n=8). The rate of oxygen consumption to glucose is higher than ofgalactose, indicating that glucose is a better substrate for Rhodotorulamucilaginosa than that of galactose. The presence of Cu ions influence the yeastcells with a decreasing in oxygen consumption.]