Judul: Optimasi Suhu Dan Lama Inkubasi Pada Hidrolisis  In Situ Minyak Jarak Pagar Untuk Produksi  Surfaktan Mono- Dan Digliserida
Abstrak: The increasing of people population in the world and also the increasing of technology development can support the invention of human need products. Surfactant is a component that can be used as mixing solution for many products. Its amphiphilic character can be used widely in many applications and have increasing usage for each year. Surfactant production based on vegetable oil such as mono- and diglyceride can be obtained from Jatropha oil because it has high productivity and high vegetable oil component. Effective and efficient method to produce mono- and diglyceride can be done with in situ hydrolysis method that is affected by temperature and incubation time. The research purposes are to obtain the effect of temperature and incubation time of Jatropha seed on in situ hydrolysis on surface tension, interfacial tension, emulsion stability, acid value, saponification value, and refractive index parameter, and also to determine optimum condition of physical characteristic of the surfactant (surface tension). The eksperimental design of this research is two level factorial design with two factors, wich were temperature and incubation time. The lowest temperature of incubation is at 33○C and incubation time of 3 days, the highest temperature of incubation is at 37○C and incubation time of 7 days. Meanwhile, the method used to find optimum condition is Response Surface Method. Surfactant M-DG that was produced can decrease water surface tension of 34−40 dyne/cm. It has interfacial tension value about 8−12 dyne/cm, emulsion stability of 48.1−59.49%, acid value of 25.81−67.11 mg KOH/g of oil, saponification value of 135.38−199.57 mg KOH/g of oil, and refractive index about 1.3777−1.4762. The microbiological analysis showed the increasing number of Mucor sp., the producer of lipase 1,3-regiospecific in Jatropha seed after incubation process. Based on the statistical analysis of factors involved, it can be concluded that incubation temperature has negative correlation to surface tension (93.87%), interfacial tension (93.79%), acid value (82.61%), and refractive index (63.93%). It has positive correlation to emulsion stability (92.72%) and saponification value (99.23%). The incubation time has negative correlation to surface tension (92.64%), interfacial tension (89.67%), and refractive index (65.76%), and has positive correlation to emulsion stability (69.98%), saponification value (97.67%), and acid value (96.77%). From Response Surface Method analysis, it can be obtained at the best condition to decrease surface tension to a minimum value of 33.42 dyne/cm with incubation temperature at 36.11○C and incubation time of 7.32 days.
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Judul: Optimasi laju alir udara dan lama inkubasi pada hidrolisis in situ minyak jarak dalam biji jarak untuk produksi surfaktan M-DG
Abstrak: Surfaktan adalah senyawa aktif penurun tegangan permukaan (surface active agent). Kebutuhan surfaktan terus meningkat setiap tahunnya dan hampir seluruhnya impor. Salah satu cara untuk mengatasinya adalah dengan adanya produksi surfaktan berbasis bahan alami seperti monogliserida dan digliserida (MDG). Tanaman jarak (Ricinus communis) merupakan komoditi yang potensial ,dilihat dari kandungan minyak dan produktivitasnya sebagai bahan baku pembuatan surfaktan M-DG. Produksi surfaktan M-DG dari biji jarak dapat dilakukan dengan hidrolisis. Pada penelitian ini dilakukan hidrolisis secara in situ untuk mendapatkan surfaktan M-DG. Hidrolisis in situ memanfaatkan enzim lipase yang terkandung dalam biji jarak serta mengatur kondisi proses sehingga mikroorganisme penghasil lipase spesifik dapat tumbuh.
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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