Judul: Bioremediasi Tanah Tercemar Diazinon Secara Ex Situ dengan Menggunakan Kompos Limbah Media Jamur (Spent Mushroom Compost)
Abstrak: Pesticide is a xenobiotic compound and rexalcytran which should be handled seriously in order to prevent human and environment from those negative effects. One of the methods which can be utilized is bioremediation technique which is utilizing fresh spent mushroom compost (SMC). The diazinon contaminated soil whith the concentration of 500 ppm, 1000 ppm and1500 ppm, was added with SMC of 10%, 20% and 30%, then incubated for 28 days. The reduction of diazinon concentrate was analyzed every week through extracted sample with etyl acetat and measured by spectrophotometer. The data processing was conducted by using respon surface method (RSM). Based on this analysis, the maximum point of diazinon concentrate reduction was 88% with the treatment of combination of 30% compost and 1000 ppm diazinon, it was obatined on the 14th. On the 21st day the diazinon concentration reduction was 91.8%. It was the result from combination of 25% compost and 1000 ppm diazinon. On 28th day, the diazinon concentration reduction was 97.5%, result from the treatment of 26% compost and 1000 ppm diazinon. The diazinon degradation process can be effectively ferformed by adding 15-30% compost, with 1000 ppm of diazinon within 21 days incubation. Some of bacteria have been isolated from SMC. that were, Bacillus mycoides, Bacillus cereus, Bacillus brevis, Pseudomonas stutzeri, dan Chromobacterium spp. Those bacteria were able to growth in solid medium which contains diazinon up to 500 ppm, except Bacillus brevis. The ability of bacteria to degrade diazinon based on their properties is forming a clear zone around the colony which is growth in solid medium of mineral salt peptone yeast (MSPY). Apparently, it is only Bacillus cereus is able to degrade diazinon up to 1700 ppm.
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Judul: Elimination of diazinon in synthetic liquid waste by spent mushroom compost biofilter
Abstrak: Diazinon is a xenobiotic and recalcitrant compound that must be controlled seriously to protect humans and the environment from negative impacts. One method for removing diazinon from the environment is bioremediation with the use of a biofilter. The biofilter used in this study was spent mushroom compost (SMC). The research objectives were to analyze the effect of compost as a biofilter and the initial concentration of diazinon solution on a decreased of diazinon concentration, to analyze the optimum amount of compost and the initial concentration of diazinon solution that have produce a maximum decrease of diazinon concentration, and to identify the survival of bacteria in the high concentration of diazinon contaminated compost. The optimization method used was the response surface method (RSM). Different concentrations of diazinon solution were used, namely 500 ppm, 1000 ppm and 1500 ppm, added into the biofilter SMC, and then incubated for 9 days for the batch system and 4 days for the semi-continuous system. The compost used in the study ranged from 300-500 g. A decreased diazinon in the Batch systems was analyzed daily and in the semi-continuous system for hour/day. The results of the study indicated that in the optimum condition of the batch system with the amount of SMC compost of 499 g and the diazinon concentration of 685.68 ppm, a maximum decrease of 100% was reached for diazinon concentration at the 192th hour and in the semi-continuous system with the SMC compost of 493 g and the diazinon concentration of 562.72 ppm, the maximum decrease of 100% was obtained for the diazion concentration at the 75th hour. Bacteria that could survive in the SMC compost with a high concentration of diazinon (1707 ppm) were Pseudomonas stutzeri, Bacillus cereus, Bacillus brevis, Bacillus azotoformans and Micrococcus agalis sp. Further, the biofilter system with SMC is a good alternative for pesticide biodegradation.
Keyword: elimination, diazinon, biofilter, spent mushroom compost, degrading, Synthetic Liquid Waste, response surface method, pesticide biodegradation

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