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: Optimasi lingkungan tumbuh mikroalga dari kawah ratu Sukabumi yang berpotensi sebagai sumber biodiesel
Abstrak: Microalgae is a potential as a source for biodiesel and can be cultured in a large scale. The objective of this study was to optimize growing environment (nitrogen consentration in media and light intensity) for microalgae from Kawah Ratu Sukabumi. Microalgae that was previously isolated and cultured, identified and examined for the lipid content using Nile Red method. Microalgae was then grown in the media with different concentrations of nitrogen (0, 0.5, 1 and 2 M) and light intensities (105, 140, 70, 175 mmol photon/m2 / s) over 16 days. Lipid content is monitored at 16 day after inoculation. Based on lipid content, only Chlorella sp. from Kawah Ratu that was potential as a raw material for biodiesel. Chlorella sp. grew the best in media BG11 containing of 750 ppm nitrogen under 70 μmol foton/m2/s light intensity. The highest lipid productivity was produced (10.8 mg/l/day) when it was grown on media BG11 under 70 μmol foton/m2/s light intensity.
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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