Judul: Pemanfaatan Limbah Karagenan Kappaphycus alvarezii Dotty dalam Proses Pembuatan Bioetanol
Abstrak: Seaweed K. alvarezii Dotty is the raw material for the manufacture of carrageenan, if one kilogram of seaweed are processed into carrageenan it will produce 0.2 kg of carrageenan and 0.1 kg of solid waste. Existing condition of carrageenan processing industries in Indonesia are only able to process 20% from the total production of seaweed (540,000 dry tons per year), it will generate solid waste of 10 800 tons per year. Hemicellulose and cellulose components contained in the processing waste of carrageenan and they are potentially to be used as bioethanol feedstock. As a raw material on producing of bioethanol, seaweed has advantage in compared to the materials derived from terresterial plants from of high lignin components while lignin in seaweed contains in low of 1 to 7%. Lignin contents in seaweed and terresterial plants can inhibit hydrolysis and fermentation process. This study aims are to determine the concentration of sulfuric acid and optimum hydrolysis time and fermentation to produce bioethanol from carrageenan waste of K. alvarezii Dotty. This experiment consist of several steps, there are (a) preparation and characterization of waste materials from carrageenan K. alvarezii Dotty; (b) optimization of waste carrageenan hydrolysis K. alvarezii Dotty using H2SO4 in different concentrations of 0%, 1%, 2%, and 3% with hydrolysis time of 15, 30 and 45 min; (c) the adaptation of yeast S. cerevisiae on waste hydrolyze media carrageenan K. alvarezii; and (d) optimization of fermentation of 2, 3, 4, 5, 6, and 7 days on carrageenan waste K. alvarezii. Factorial completely randomized design was used in the hydrolysis experiment with H2SO4 concentration and hydrolysis time as dependent variables; while in the fermentation step, descriptive analysis was performed. The chemical composition of the waste carrageenan are moisture, ash, protein, carbohydrate and crude fiber. Carrageenan waste contained carbohydrate and crude fiber of 11.36% and 11.64%, respectively. Crude fiber in the form of hemicellulose was found in waste carrageenan by 12.86%, while cellulose and lignin were not detected. These components can be hydrolyzed and fermented into bioethanol. Concentration of H2SO4 gave a significant effect on reducing sugar content (p<0.05), whereas the time of hydrolysis was not significant (p>0.05). The highest reducing sugar content of hydrolysis from carrageenan waste obtained in H2SO4 concentration of 1% for 15 minutes was 17.90% (b/v). The fermentation process was conducted by using the yeast S. cerevisiae AL IX which has been adapted on hydrolyze media carrageenan K. alvarezii Dotty waste for 2 times. During the four days of fermentation, ethanol production was higher of 12.41% (v/v). Types of alcohol obtained in fermentation experiment was ethanol, with value was 4.78%; whereas methanol and propanol were not detected.
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Judul: Produksi Bioetanol dari Rumput Laut Kappaphycus alvarezii Menggunakan Khamir Saccharomyces cerevisiae IPBCC ALXVII
Abstrak: Kappaphyus alvarezii contains carrageenan type polysaccharide which consists galactose as its monomers. After acidly hydrolysis process, galactose can be converted into ethanol through fermentation process. However, some yeasts prefer glucose as their food substrate. One of the yeast from Surfactant and Bioenergy Research Centre (SBRC) Laboratory is Saccharomyces cerevisiae IPBCC ALXVII is expected can convert galactose inside hydrolyzed seaweed into ethanol. This study aims to analyze the potential of S. cerevisiae IPBCC ALXVII in production of ethanol from K. alvarezii seaweed. In this study, the inoculum of S. cerevisiae IPBCC ALXVII was prepared by repeated batch for eight times. Fermentation process used two hydrolyzed seaweed with different concentrate of sugar reductor. Fermentation with 150.46 g/L sugar reductor concentrate produced lower content of ethanol i.e. 1.69 g/L while with 57.33 g/L produced the highest content of ethanol i.e. 14.56 g/L with fermentation efficiency about 49.80%. The optimum fermentation time using S. cerevisiae IPBCC ALXVII was 144 hours.
Keyword: Bogor Agricultural University (IPB), energy, ethanol, hydrolysis, Kappaphycus alvarezii

Judul: Invers dari Matriks Tridiagonal Jacobi
Abstrak: Suatu matriks berukuran n×n dinamakan matriks tridiagonal jika untuk . Karya ilmiah ini memberikan algoritma yang mudah untuk menemukan invers ( dari matriks tridiagonal Jacobi yang simetrik dan nonsimetrik. Setiap elemen pada matriks tridiagonal ini adalah bilangan real. Terdapat 3 lema dan 2 teorema untuk menentukan . Lema pertama menunjukkan persamaan utama dalam membuktikan lema-lema dan teorema-teorema selanjutnya. Invers dari matriks yang simetrik dibuktikan oleh lema kedua yang menunjukkan elemen-elemen baris ke- dari . Selanjutnya, lema kedua dilengkapi dengan teorema pertama yang menunjukkan elemen-elemen dengan . Invers dari matriks yang nonsimetrik dibuktikan oleh lema ketiga yang menunjukkan elemen-elemen dengan dan elemen-elemen dengan dibuktikankan oleh teorema kedua.
Keyword: symmetric, nonsymmetric, matrix