Judul: Produksi Bioetanol dari Limbah Tanaman Jagung Melalui Sakarifikasi dan Fermentasi Simultan dengan Kultur Campuran Saccharomyces cereviseae dan Pichia stipitis
Abstrak: Corn crop waste as a lignocellulosic material has a large potential in Indonesia. Lignocellulosic material is a renewable raw material for ethanol production. Most of the composition of lignocellulisic materials consist of cellulose, hemicellulose, and lignin. Cellulose hydrolysis will produce glucose that can be fermented into ethanol by Saccharomyces cereviseae. Hemicellulose hydrolysis will produce xylose. Sacharomyces cerevisiae is the most applied and traditional microorganism for ethanol production. It has a high ethanol tolerance, and high yields and rates of fermentation, but its inability to ferment xylose, the second most abundant sugar in nature, limits its use in biofuel production. This study applies simultaneous saccharification and fermentation techniques to the production of ethanol from corn crop waste materials using a culture volume Saccharomyces ceseviseae, Pichia stipitis, and mixed culture of Saccharomyces cereviseae and Pichia stipitis.Simultaneous saccharification and fermentation with individual yeasts Pichia stipitis shows the best results with high ethanol at 5.84 g/l and yield 0.11. Saccharomyces cereviseae and Pichia stipitis mixtures with etnanol 4.34 g/l and yield 0.10, and Saccharomyces cereviseae at least with the results 3.79 g/l ethanolo and yield 0.07 at the time of 96 hours. The results of this study indicate that at 96 hours of mixed culture of Saccharomyces cereviseae and Pichia stipitis not improve the performance their single culture. Further research still needs to be done by optimizing the ratio and between the two yeasts and sequence inoculation.
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Judul: Rekayasa Bioproses Produksi Bioetanol dari Hidrolisat Pati Sagu (Metroxylon sp.) Menggunakan Saccharomyces Cerevisiae Var.ellipsoides Pada Kultivasi Nir-Sinambung dan Semi Sinambung:
Abstrak: Starch of sago is one of the sources of ethanol which is able to be produced by enzymatic hydrolysis and followed by cultivation process. It has high concentration of carbohydrate (80 %), so it can produce glucose highly with enzymatic hydrolysis process. The total amount of glucose has correlation with amount of ethanol, in cultivation process. The first step of research was to prepare substrate from sago starch which was hydrolysed enzymatically using α- amylase and amyloglucosidase (AMG) enzymes. Preliminary research was conducted to determine optimum concentration in which S.cerevisiae var.ellipsoides can live and produce the highest ethanol content. The concentrations being tested were 18, 24, 30 and 36 % (g/L) of total sugar. The main research consists of two systems: batch and fed-batch. Result shows that 24 % concentration (g/L) was find to be the optimum consentration for S.cerevisiae var.ellipsoides with ethanol production reaches up to 10,2 ± 0,000 % (w/v). One of the main research is using batch cultivation. The best result of highest ethanol concent was reached (10,77 ± 0,000 % w/v) when aeration was stopped after biomass condition has reached the maximum condition. The best result on fed-batch cultivation with the highest ethanol concentration (12,05 ± 0,00 % w/v) also was gained at the same treatment with feed concentration of glucose 16 % g/L. Based on calculation of cultivation kinetic parameters, it is shown that in batch cultivation the highest Yp/s, Yp/x (0,15; 0,47; 4,48) was gained on the third treatment that is aeration stopped at 30th hour. On fed-batch cultivation, the highest Yp/s and Yp/x value (0,51 and 5,05) is shown on treatment of which aeration is stopped after 30th hour and feed concentration of 16 % g/L.
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Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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