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"Sorghum merupakan tanaman serealia yang sangat potensial untuk dibudayakan di Indonesia karena punya keunggulan dibandingkan dengan tanaman pangan yang lain. Di dalam limbah sorghum (malai dan tangkai) banyak terkandung hemiselulosa yang apabila dihidrolisis akan menghasilkan monomermonomernya. Salah satu monomer yang dihasilkan adalah xilosa yang merupakan bahan baku pembuatan xilitol. Pada penelitian ini digunakan malai dan tangkai sorghum mandau sebagai bahan untuk pembuatan xilitol. Bahan tersebut dihidrolisis menggunakan asam sulfat (H2SO4) 0,3M pada suhu 121°C dengan waktu optimum 35 menit. Hasil pengukuran kadar xilosa dalam hidrolisat pada kondisi optimum 25,70 % (w/w) untuk malai dan 20,56 % tangkai. Hidrolisat optimum ini yang akan digunakan sebagai substrat dalam proses fermentasi oleh Candida fukuyamaensis UICC Y-247 khamir penghasil enzim xilose reduktase. Hidrolisat kemudian detoksifikasi dengan menambahkan arang aktif 1% (w/v) untuk menghilangkan senyawa toksik yang dapat menghambat pertumbuhan khamir. Produk xilitol hasil fermentasi tanpa kosubstrat, konsentrasi tertinggi didapatkan waktu fermentasi 12 jam dengan persen konversi xilitol 12,88% untuk malai dan 10,88% tangkai. Produk xilitol hasil fermentasi dengan kosubstrat 7,5%, konsentrasi tertinggi pada waktu fermentasi 12 jam dengan persen konversi xilitol 18,04 untuk malai dan 16,50 tangkai. Sedangkan produk xilitol hasil fermentasi dengan kosubstrat 15%, konsentrasi tertinggi waktu fermentasi 12 jam dengan persen konversi xilitol 8,22% untuk malai 4,88% tangkai.

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Sorghum is plant which is potential to be cultivated in Indonesia since it has many advantages compared with other plants. Sorghum?s waste (stem and branch) contains which can be hydrolyzed giving its monomers hidrolized, to produce xylose. One of the monomers is xylose which the materials of xylitol.

In this research, stem and branch of sorghum are used as souce is the source for xylitol production. The material was hydrolyzed using sulfuric acid (H2SO4) 0,3M At 121 degree Celcius with optimal duration of 35 minutes. The result of measurement of xylosa contained in hydrolyzed at optimal condition 24,90 % for stem and 20,56 % for branch. This hydrolyzed was used as substrate for the process of fermentation by Candida fukuyamaensis UICC Y-247 khamir is the producer of "xylose reductate" enzyme. The hydrolyzed is then decolorized by adding active carbon 1 % (w/v) to remove toxin substance which can fermentation process by khamir growth. The product of xylitol fermentation without kosubstrat, from the highest fermentation duration 12 hours with percent coversion of xylitol 12,88 % for stem and 10,88 % or branch.

The product of xylitol from fermentation with kosubstrat 7,5 %, from the highest concentration on fermented duration 12 hours with percentage of xylitol convention 18,04 for stem and 16,50 for branch. Where as the product of xylitol fermentation with 15 % kosubstrat, with the highest yealds fermentation duration 12 hours with the percentage of xylitol convention is 8,22 % for stem and 4,88 % for branch."

"ABSTRACTIn order to shorten the measurement time of biochemical oxygen demand (BOD), a BOD sensor based on yeast metabolism was developed. Local yeast, Indonesian Origin, Candida fukuyamaensis UICC Y-247, was used as a transducer. The yeast was immobilized as a thin film in agarose matrix with the auxiliary of Nafion® acting as the membrane for ion exchange process. The film was then attached to gold-modified glassy carbons and used as transducer on the working electrodes. The measurements were conducted by observing the depletion of glucose concentration using multipulse amperometric method and then converted to BOD values. Optimum condition was observed in a waiting measurement time of 30 min at an applied potential of 450 mV (vs.Ag/AgCl). Linearity was shown in glucose concentration range of 0.1?0.5 mM, which was equivalent to BOD concentration range of 10?50 mg/L. A detection limit of 1.13 mg/L BOD could be achieved. Good repeatability was shown by a relative standard deviation (RSD) of2.7% (n = 15). However, decreasing current response of ~50% was found after 3 days. Comparing to the conventional BOD measurement, this BOD sensor can be used as an alternative method for BOD measurements. "

"Pengaruh ion Cu2+ diuji untuk sensor BOD yang sedang dikembangkan. Sensor BOD dibuat dengan menggunakan sistem sel khamir bebas untuk khamir Rhodotorula mucilaginosa UICC Y-181 dan khamir Candida fukuyamaensis UICC Y-247 pada elektroda emas. Penentuan nilai reduksi oksigen pada -600 mV (vs Ag/AgCl) ditentukan dengan cyclic voltametri. Sedangkan deteksi oksigen sisa yang tidak digunakan oleh mikroorganisme dilakukan dengan teknik multi pulse amperometry (MPA). Hasil pengukuran kalibrasi linier pada keadaan free cell untuk kedua jenis khamir menunjukkan nilai daerah kelinieran yang baik dengan nilai regresi 0,994 dan 0,987 berturut-turut untuk keadaan free cell Rhodotorula mucilaginosa UICC Y-181 dengan waktu optimum pengukuran 20 menit dan untuk keadaan free cell Candida fukuyamaensis UICC Y-247 dengan waktu optimum pengukuran 25 menit. Presisi yang lebih baik ditunjukkan dengan 15 kali pengukuran untuk khamir Rhodotorula mucilaginosa dengan nilai RSD 0,9 %, sedangkan untuk khamir Candida fukuyamaensis dengan nilai RSD 5,01%. Pengaruh keberadaan logam berat pada sistem pengukuran dilakukan dengan menvariasikan konsentrasi ion Cu2+. Sensor BOD dengan Rhodotorula mucilaginosa menunjukkan ketahanan yang lebih baik terhadap kehadiran ion Cu2+ seperti ditunjukkan oleh sedikitnya kenaikan arus oksigen dibandingkan dengan kenaikan arus oksigen pada sensor BOD dengan Candida fukuyamaensis.

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Influence of copper ions was examined on developed microbial BOD sensors.The BOD sensors carried out in a system consisted of free cell yeast and gold electrode. Rhodotorula mucilaginosa UICC Y-181 and Candida fukuyamaensis UICC Y-247 were used as the microbial yeasts. Oxygen reduction potensial of -600 mV (vs Ag/AgCl) was determined by using cyclic voltametry, whereas the excess oxygen concentration, which not used by microorganism, was determined by multy pulse amperometry (MPA). Optimum waiting times of 20 and 25 min were obtained for BOD sensors of Rhodotorula mucilaginosa UICC Y-181 and Candida fukuyamaensis UICC Y-247, respectively. Linear calibration curves showed good linearity with linear regressions of 0.994 and 0.987 for those of Rhodotorula mucilaginosa UICC Y-181 and Candida fukuyamaensis UICC Y-247, respectively. However, better precision of measurement (n=15) was shown by an RSD of 0.90% for Rhodotorula mucilaginosa, whereas it was 5.01% for Candida fukuyamaensis. Influence of copper ions was examined in various concentrations of Cu ions. BOD sensor of Rhodotorula mucilaginosa shows better resistance against Cu ions than that of Candida fukuyamaensis, as it is shown by less increasing of oxygen current at Rhodotorula mucilaginosa than that at Candida fukuyamaensis."