Judul: Identification and optimization of growth media of microalgae originated from Cipanas hot spring water West Java that is potential for biodiesel source
Abstrak: The increasing use of fossil fuel leads to the depletion of fuel sources and increases CO2 emission level into the environment that affects global warming. Microalgae is an alternative biodiesel source that is renewable and environmentally friendly. The objective of the research was to identify and optimize the growth media of microalgae isolate originated from Cipanas hot spring water. Identification was done based on morphological and 18S rDNA gene sequence approaches. Growth media experiment was designed as a factorial randomized block design. First factor was water media composition containing aquades and hot spring water with five level of aquades:hot spring water ratio, which were 1:0, 0:1, 1:1, 2:1, and 1:2 (v/v). The second factor was P concentration, which were 40, 80 and 120 ppm. The result showed that the morphologically a microalgae isolate had similarity to Chroococcus sp prokaryotic, but molecular data indicated that the microalgae was similar to uncultured freshwater eukaryote clones. The highest cell density of microalgae culture was 2.19 and 2,21 which were achieved when microalgae was cultured in aquades:hot spring water medium 1:2 (v/v) and in P concentration 120 ppm, respectively. The highest dry weight average of biomass (175 mg) was obtained in aquades:hot spring water 1:0 (v/v) with P concentration 120 ppm. Hot spring water could be substituted by aquades to gain high lipid content microalgae. Growth media containing aquades:hot spring water 1:0 (v/v) with P concentration 40 ppm produced the highest average of lipid content (21%) and highest average of lipid productivity, 17 mg l-1 day-1.
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Judul: Produksi lipid dan karbohidrat ganggang mikro asal sawah dan perairan tawar yang dikultivasi pada skala lapang
Abstrak: Production of bioenergy as an alternative for oil fuel requires biomass as raw material. With an extremely rapid growth rate, microalgae is potential to be developed as a source of bioenergy by extracting lipids and carbohydrates from its biomass. This research was initiated by a laboratory-scale cultivation of 4 isolates of microalgae (ICBB 9111, ICBB 9112, ICBB 9113, and ICBB 9114) in 50 ml medium with 5 different concentrations, i.e. 0.75 times the standard media M4 composition (0.75 M4), M4, 1.25 M4, 1.50 M4, and 1.75 M4. The composition of M4 standard media (g/L): 1.5 NaNO3, 0.049 K2HPO4, 0.0366 MgSO4, 0.0271 CaCl2, 0.006 citric acid, 0.006 Fe-ammonium citrate, 0.001 EDTA, 0.02 Na2CO3 and 1 ml micro nutrient with composition (g/L): 2.86 H3BO3, 0.1485 MnCl2, 0.1245 ZnSO4, 0.0506 Na2MoO4.2H2O, 0.0506 CuSO4, and 0.043 CoCl2.6H2O. The laboratory scale growth-rates of microalgae at different compositions of standard media were varied. Based on the results of analysis of variance, Duncan's Multiple Range Test, and growth chart, the optimum medium for the field-scale cultivation were 0.75 M4 for microalgae ICBB 9112 and ICBB 9114, and M4 for microalgae ICBB 9111 and ICBB 9113. The growth rate of microalgae at field scale was faster than those at laboratory one. The average biomass productivity of microalgae ICBB 9111, ICBB 9112, ICBB 9113, and ICBB 9114 after cultivated for 2 days at field scale were, respectively, 0.28, 0.21, 0.26, and 12.32 g/L. The highest lipid production was produced by isolate ICBB 9114 (32% w/w) at 0.75 M4 medium, and the highest carbohydrate production was obtained from isolate ICBB 9113 (44% w/w) at M4 media. This result indicates that when the microalgae lipid production is high, the corresponding carbohydrate production is lower and vice versa.
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf