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 Etanol dari Rumput Laut Sargassum sp. dan Limbah Agar Gracilaria sp.
Abstrak: Nowadays, problems in the scarcity energy is big problem faced by human. This problem emerges because most energy sources come from fossil fuel that having limitation in its availability. Beside that, combustion of fossil fuel results negative impact to the environment. Therefore, exploration of a new fuel which more safe for environment and renewable is required. One of solution to overcome the problems in energy source is by using bioethanol,which can be produced from biomass contains sugars in its chemical composition. Seaweed has high potency as feedstock to produce bioethanol because having high content of carbohydrate, simple cultivation technology, wide cultivation area as well as harvest time that is relatively short ( range around 4 to 6 weeks) and good CO2 absorption abilty. Indonesia has many diversity in seaweed species, and potentially used as raw material for hydrocolloid industry, such as Porphyroglossum sp., Pterocladia sp., Sargassum sp., and Gracilaria sp. In this research fresh Sargassum sp. and agar waste of Gracilaria sp. were used as fuel feedstock in bioethanol production. The results from proximate analysis for Sargassum sp. showed that major components were mineral/ash and carbohydrate, while for agar waste of Gracilaria sp. was crude fiber. High component especially in carbohydrate and crude fiber contents showed its potency as carbon source for bioethanol fermentation. On the pretreatment using acid hydrolysis, high soluble sugars produced from Sargassum sp. was obtained from acid hydrolysis using H2SO4 concentration of 2 % for 20 minutes which result 0.649 g/l of reducing sugar and 1.015 g/l of total sugar, while for agar waste of Gracilaria sp. was obtained from acid hydrolysis using H2SO4 concentration of 1.5 % for 10 minutes which result 0.157 g/l of reducing sugar and 0.205 g/l of total sugar. From result of fermentation analysis, for the fermentation of Sargassum sp. yielded ethanol 0.18 % (v/v) while for the fermentation of agar waste of Gracilaria sp. yielded ethanol 0.11 % (v/v). This low ethanol rate yields probably becaused by the low availibility of sugar as well as existence of yeast growth inhibitor compound and poison like furfural in acid hydrolysis further products.
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Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh.
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. ,,,
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular.