Judul: Aktivitas Amilolitik Beberapa Kapang dan Kemampuan Produksi Alkoholnya dari Pati Singkong
Abstrak: Bioethanol is a renewable energy, that is produced from starch by enzymatic process. The aim of this research was to select potential fungi which were able to produce glucoamylase and subsequently convert glucose to ethanol. Four out of 32 isolate molds of Institut Pertanian Bogor Culture Collection (IPBCC), that were Aspergillus niger IPBCC 88.145, Trichoderma longibrachiatum IPBCC 07.556, Penicillium sp. IPBCC 07.537, and P. herquei IPBCC 07.557 had amylolytic activity. Aspergillus niger IPBCC 88.145 had the highest amylolytic index 2.7 with optimum activity of glucoamylase (1.95 Unit/mL) at 96 hours of incubation. Based on the CO2 loss conversion, ethanol production from 1% (b/v) cassava starch by A. niger IPBCC 88.145 increased up to 192 hours of incubation with total production approximately 4.13 mL. Alcohol production from sterilized cassava slurry (50%) had the efficiency of alcohol production about 52.11% (v/v) with total volume of alcohol 7.25% (v/v), and alcohol concentration 90.5%. While that of pasteurized cassava slurry had the efficiency of alcohol production about 55.71% (v/v) with total volume of alcohol 7.75% (v/v), and alcohol concentration 93.5%.
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Judul: Produksi Bioetanol dari Hidrolisat Pati Singkong Racun dengan Fermentasi Repeated-Batch oleh Saccharomyces cerevisiae Terimobilisasi pada Ampas Singkong
Abstrak: Bioethanol production by batch fermentation using free cells has low productivity and efficiency. Furthermore, bioethanol production based on cassava starch produces bagasse as by-product which has not been utilized optimally. In this research, Saccharomyces cerevisiae was immobilized on cassava bagasse. This research aim to study bioethanol production from cassava starch in repeated-batch fermentation by Saccharomyces cerevisiae immobilized on iii cassava bagasse. Research method consists of starch extraction, starch hydrolysis, cassava bagasse treatment by HCl 3% (v/v), immobilization of Saccharomyces cerevisiae on cassava bagasse, and fermentation by repeated-batch method. The resulting yield of starch was 26.20% (w/w) and conversion efficiency of starch to hydrolyzed starch was 36.89% (w/w). The use of cassava bagasse treated by HCl 3% (v/v) is capable to immobilize 1.76x1011 cells/g carrier. The resulting ethanol concentration was 42.72-63.66 g/L, productivity 1.78-2.66 g/L/h, sugar conversion 90.80-95.74%, yield 0.33-0.47 g/g, and efficiency 65.91-93.13%. This result showed that ethanol production with repeated-batch fermentation by Saccharomyces cerevisiae immobilized on cassava bagasse has good stability, high productivity, sugar conversion, and efficiency.
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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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