Judul: Studi degradasi mikrobiologi minyak dalam sedimen pantai
Abstrak: Research with topic Study of Microbial degradation in coastal sediment had been conducted at Laboratory Microbiology of Oceanography Research Center - Lembaga Ilmu Penelitian Indonesia (P2O-LIPI) Ancol, North Jakarta from March until May 2010. Parameters measured were dissolved oxigen, pH, electrical conductivity, temperature, nutrient, and oxidation-reduction potential. Analysis including decreasing of oil weight using gravimetric method, total number of bacterial cells using Acridine Orange Direct Count method, and hydrocarbonoclastic bacteria using Most Probable Number method. Parameter differences inter-treatment and inter-time seen by using split plot design. Balongan coastal sediment form very fine sand with grain diameter ranged 150-290 μm are 85,261%, >290 μm are 6,853%, and <150 μm are 7.886%. Quality of media monitored during bioremediation trial were declining, such as dissolved oxigen, pH, and oxidation-reduction potential. Only electrical conductivity shown relatively stable values during 28 days of incubation period. Observation result show that there were slight differences in nitrogen content of fertilizer Osmocote (2,2129 mg/L), Terra (2,2581 mg/L), Dekastar (2,0323 mg/L), and Multi cote (1,8065 mg/L). Phosphat content on treatments too show slight differences, Osmocote (0,9463 mg/L), Terra (0,8811 mg/L), Dekastar (0,8484 mg/L), dan Multi cote (1,0116 mg/L ). Oil degradation rate from 0 day until 28th day on treatment with Osmocote (0,3191 mg/day) show the highest value, followed by Dekastar (0,2732 mg/ day), Terra (0,2717 mg/ day), Multicote (0,2589 mg/ day), control positive (0,1024 mg/ day). Osmocote is the most effective among tested slow release fertilizers for stimulating indigenous hydrocarbonoclastic microbial activity in coastal sediment at Balongan, Indramayu, West Java. Effect of nutrient addition is increasing biomass and bacterial growth rate and increasing crude oil biodegradation rate in polluted sediment.
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Judul: Bioremediation Process of Petroleum-Contaminated Coastal Sand using Oil Spill Dispersant (OSD) and Indigenous Bacteria
Abstrak: Oil pollution in coastal areas due to oil spills is an environmental issue that needs a further concern. Several oil spills have been occurring frequently in the worldwide, such as at Malacca strait and the Northern coast of West Java Province. Crude oil contains persistent organic pollutants (POPs) that are difficult to degrade. This study aimed to obtain bacterial strains that could degrade crude oil, through bacterial isolate characterization, and crude oil biodegradation test in a crude oil-enriched microcosm model. Bacterial isolation was carried out by crude oil enrichment in the bacterial, followed by the bacterial purification, characterization, and identification. From the isolated bacteria, two strains were selected with a higher TPH degradation value, namely CYA20 and CYA27. The CYA20 was tolerant to NaCl up to 4%, while the CYA27 could grow up to 12% NaCl concentration. The strain was also tolerant to the pH of 5 – 9 and temperature of 10 – 50 oC. Both strains were observed to utilize POPs, such as phenanthrene and fluorene. Both strains could produce biosurfactants and perform an emulsification activity in paraffin from 0.373-0.533. Based on the phylogenetic analysis, these bacterial strains are identified as Acinetobacter baumannii CYA20 and Bacillus subtilis CYA27, respectively. Therefore, both strains have the potential as biodegradation agents developed in the bioremediation process of crude oil-contaminated environments.
Keyword: Acinetobacter baumannii, Bacillus subtilis, Bioremediasi, Crude oil, Dispersan, Poliaromatik hidrokarbon

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