Judul: Hidrolisis Enzimatik untuk Meningkatkan Produksi Bioetanol dari Makroalga (Eucheum cottonii)
Abstrak: Bioethanol is ethanol produced from the fermentation of glucose and followed by distillation process. One of alternative to replace bioethanol feedstock is using seaweed (Eucheuma cottonii) as raw material substitution. The common process for producing bioethanol are acid and enzymatic hydrolysis, but in this research only focused on enzymatic hydrolysis. The enzymes that used were Cel 150 and xylanase, with additional of acid hydrolysis before the application of enzymatic hydrolysis. Incubation time and enzymes concentration in the hydrolysis step are crucial factor to improve reducing sugar value in increasing bioethanol yield from macroalgae. The treatment was done in each enzyme concentration of 1, 3, 5, 7.5 and 10% with incubation period of 1, 2 and 3 days, for getting the highest percentage of reducing sugar. The result obtained that average of the highest reducing sugar was done on concentration of 7.5% using Cel 150 in two days incubation time and 3% for xylanase within one day incubation period. The lowest average of total solid value for Cel 150 is done in concentration 5% on 3 days incubation time and at same precent of concentration for xylanase on 2 days incubation period. The increasing reducing sugar for Cel 150 and xylanase enzymes with the best concentration and incubation period is 57.69% and 5.37%. The best treatment of each enzyme fermented using Sacaromices cereviceae for four days to get ethanol. The results were 1.46% and 0.31% for cel 150 and xylanase. The result show that concentration and incubation period for enzymatic hydrolysis process have noticeable influence for total reducing sugars value.
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Judul: Fermentation modification of acid hydrolisates of euchema cottonii to produce bioethanol using Saccharomyces cerevisiae and Pachysolen tannophilus.
Abstrak: Euchema cottonii is a red algae that is formed from linear polysaccharide commonly called "carrageenan". Carrageenan is galactan (polysaccharide sulfate linear hydrophilic) which is a polymer consists of galactose. The research objective is to modify bioethanol fermentation by batch condition from seaweed (Euchema cottonii) acid hydrolisates to produce a high yield of bioethanol. The study was conducted in two stages. The first stage is a preliminary phase which consists of size reduction, drying, characterization of E. cottonii with parameters tested were carbohydrates (cellulose and hemicellulose), protein, crude fiber, ash, and water content. The last stage is the preliminary were hydrolysis of E. cottonii using sulfuric acid so that the cellulose and hemicellulose components of E. cottonii can be hydrolyzed into constituent sugars (galactose) and then filtered the results so obtained solids hydrolysis and hydrolyzate containing galactose. The second stage is the stage of primary research which is divided into two stages, adaptation stages and fermentation stages. In the adaptation phase, yeast was adapted in media containing galactose to condition the yeast in media containing galactose. The second stage is the fermentation of acid hydrolisates of E. cottonii to produce bioethanol using two kinds of yeast that has been adapted (Saccharomyces cerevisiae IPBCC AL IX and Pachysolen tannophilus IPBCC AC IX). For the fermentation process, the medium of acid hydrolisates of E. cottonii added vitamins, nitrogen, and minerals (trace elements) to spur the growth of activity in the yeast consumes galactose to produce bioethanol. Euchema cottonii has high polysaccharides content and those can be converted into fermentable sugar through acid or enzymatic hydrolysis. Polysaccarides of red algae Euchema cottonii consists of 29.45% (db) carbohydrates, 3.21% (db) hemicelluloses, and 11.30% (db) celluloses. Type of sugar was obtained in acid hydrolisates of Euchema cottonii consists of 4.95% galactose, 0.25% glucose, 0.04% xylose, and 0.02% maltoheptaosa. The highest ethanol production from adapted Saccharomyces cerevisiae IPBCC AL IX was 2.38% (v/v ethanol in fermentation broth), with 79.09% substrate efficiency and 56.30% fermentation efficiency for 6 days incubation. The highest ethanol production from adapted Pachysolen tannophilus IPBCC AC IX was 0.11% (v/v ethanol in fermentation broth), with 15.39% substrate efficiency and 2.60% fermentation efficiency for 4 days incubation. The highest ethanol production with refreshed culture treatment using adapted Pachysolen tannophilus IPBCC AC IX after fermentation lasts 24 hours by adapted Saccharomyces cerevisiae IPBCC AL IX was 0.81% (v/v ethanol in fermentation broth), with 82.42% substrate efficiency and 19.79% fermentation efficiency for 6 days incubation. The highest ethanol production with refreshed culture treatment using adapted Saccharomyces cerevisiae IPBCC AL IX after fermentation lasts 24 hours by adapted Saccharomyces cerevisiae IPBCC AL IX was 1.76% (v/v ethanol in v fermentation broth), with 53.06% substrate efficiency and 43.53% fermentation efficiency which fermented for 6 days. The highest ethanol production with different of reducing sugar concentration treatment on media of fermentation after 6 days incubation was 2.13% (v/v ethanol in fermentation broth), with 76.31% substrate efficiency and 50.97% fermentation efficiency with reducing sugar consentration on media in the start of fermentation was 6.57% (w/v).
Keyword: bioethanol, yeast adaptation, Euchema cottonii, Pachysolen tannophilus, Saccharomyces cerevisiae, refreshed culture treatment, reducing sugar consentration treatment

Judul: Transisi Fasa Materi Hadronik ke Materi Kuark pada Inti Bintang Neutron.
Abstrak: Bintang neutron terdiri dari beberapa lapisan yang disusun oleh materi nuklir yang berbeda dengan kerapatan yang semakin tinggi ketika mendekati pusat bintang. Inti luar bintang neutron disusun oleh materi hadronik (nukleon, lepton, dan hyperon), sedangkan inti dalam bintang neutron disusun oleh kuark-kuark bebas (up, down, strange) yang saling berinteraksi. Tujuan penelitian ini adalah mempelajari bagaimana transisi dari inti luar ke inti dalam bintang neutron dengan menggunakan pendekatan RMF (Relativistic Mean Field) untuk materi hadronik dan CIDDM (Confined Isospin Density Dependent Mass) untuk materi kuark. Tekanan transisi diperoleh ketika potensial kimia barion materi hadronik dan materi kuark bernilai sama. Nilai tekanan transisi dengan parameter SU6-TM1 sekitar 87 MeV/fm3 dan diperoleh massa maksimum bintang neutron yaitu 1.92M dengan jari-jari sekitar 8.62 km. Nilai tekanan transisi dengan parameter SU6-G2 sekitar 53 MeV/fm3 dan massa maksimum bintang neutron yaitu 1.88M dengan jari-jari sekitar 8.16 km. Jenis transisi fasa adalah orde satu ditandai dengan diskontinuitas dalam kerapatan energi (adanya mixed phase). Parameter-parameter pada model nuklir yang digunakan menyebabkan perbedaan kekakuan persamaan keadaan (EOS) dari materi hadronik dan materi kuark sehingga nilai tekanan transisi dari fasa hadronik ke fasa kuark juga berbeda.
Keyword: bintang neutron, persamaan keadaan, transisi fasa