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: Isolation of deep-sea sediment bacteria for oil spill biodegradation
Abstrak: The potency of deep-sea sediments bacteria is still unfamiliarly used for oil spill biodegradation, and this research was to isolate and identify bacteria from those sediments and adapt them in oily media. Bacterial isolates were cultivated and adapted in a mixture of 0.1% v/v crude oil media. Seven deep-sea sediment samples were treated to isolate bacteria and it produced a variety of bacteria population 5.5 x 102 CFU mL-1 to 1.5 x 106 CFU mL-1. These populations apparently increased after cultivation and adaptation and gave a varying population from 3.0 x 106 CFU mL-1 to 6.8 x 108 CFU mL-1. The increased bacteria population was an indication of the bacterial capability of using carbon in crude oil as a substrate. Those bacteria were Raoultella sp., Enterobacter sp. and Pseudomonas sp., Potensi bakteri sedimen laut dalam untuk teknologi biodegradasi tumpahan minyak masih belum banyak dimanfaatkan. Tujuan dari penelitian ini adalah mengisolasi dan mengidentifikasi bakteri alami dari contoh sedimen laut dalam, dan menyesuaikannya dalam media yang berminyak. Isolat bakteri dikultivasi dan diadaptasi menggunakan media air laut terkondisi nutrien yang dicampur dengan minyak mentah 0.1% v/v. Isolasi dari 7 contoh sedimen laut dalam menghasilkan jumlah populasi bakteri 5.5 x 102 CFU mL-1hingga 1.5 x 106 CFU mL-1. Setelah kultivasi dan adaptasi dilakukan, populasi bakteri meningkat yaitu sebesar 3.0 x 106 CFU mL-1 hingga 6.8 x 108 CFU mL-1. Peningkatan tersebut mengindikasikan bahwa bakteri mampu menggunakan karbon pada minyak mentah sebagai sumber nutrisi. Bakteri yang teridentifikasi dalam penelitian ini diantaranya Raoultella sp., Enterobacter sp. Dan Pseudomonas sp.
Keyword: Bacteria, Biodegradation, Deep-sea Sediment, Isolation, Oil Spill

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