Judul: Pemanfaatan Substrat Molasses dan Urea Pada Produksi Biopestisida oleh Bakteri Endofit (Pseudomonas putida) Menggunakan Bioreaktor Kolom Gelembung
Abstrak: The main constraint in the cultivation of nilam (patchouli) is the decrease its production after being harvested 3-4 times. This is due to disease attacks, particularly nematode-a type of disease called Pratylenchus brachyurus. Besides inhibiting the plant growth, an infection of P. brachyurus also decreases the chlorophyll content and oil content of patchouli. A biological control using endophytic bacteria is one alternative to overcome this problem. For the ease of application in the field, the bacteria should be formulated and propagated. The propagation formulation is done by modifying cultivation media. This research aimed to study the utilization of molases and urea on the growth media of endophytic bacteria (Pseudomonas putida) by using a bubble column bioreactor, to get the best cultivation media formulation to produce the highest biomass dry weight, and to measure bacterial filtrate toxicity as a result of cultivation against nematodes (target mortality rate). This study included an analysis of pre-cultivation, during the cultivation process and post cultivation using a completely randomized experimental design of one factor. The factor used was the molases content consisting of 3 levels (molases of 1%, 1.25% and 1.5%) and urea content of 1%. The cultivation was carried out in a bubble column bioreactor with temperature of 25-30ºC, initial pH of 6.8-7.3 and aeration of 0.5v/v/m. The observation was conducted every 6 hours for 48 hours. The result showed that the formulation of media influenced the changes in pH and biomass formation. A molases content of 1.5% and urea content of 1% had the highest dry weight biomass, namely 3.495 (g/l). The efficiency value of the highest substrate utilization in a molases concentration of 1.5% and urea of 1% was 72.10%, with the highest cultivation kinetic parameters in the form of μmax of 0.147/hrs and a td-x of 4.714 hours. The highest value of Yx/s occurred at the molases concentration of 1.5% and urea of 1% for 0.257±0.067 g biomass per g substrate. The highest nematode mortality was at the molases concentration of 1.5% and urea of 1%, which had a positive correlation with dry weight biomass.
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Judul: Pengaruh Aerasi terhadap Produksi Biopestisida oleh Pseudomonas putida Menggunakan Substrat Limbah Cair Tahu
Abstrak: Biopesticides is pesticide containing microorganism like bacteria, viruses, and fungal that are used to control pest. Biopesticides from endophitic bacteria are used to control nematode P. brachyurus. Endophitic bacteria are bacteria that colonize plant tissue without disturbing the plant. Pseudomonas putida is one of the endophitic bacteria that have the potency to control soil borne pathogen with antibiotics and siderophore from their activities. One of substrates that can be used as cultivation media is tofu waste. This waste come from filtration of soybean extract to make tofu through protein fractionation of soybean extract. This substrate contain organic material such as protein, fat, carbohydrate, and others which are useful for bacteria growth. One of the important factors for aerobic cultivation is aeration. The main function of aeration is as oxygen source to bacterial metabolism and homogenity on the medium. The objectives of this research are to produce biopesticides from Pseudomonas putida using tofu waste as substrate, and to determine aeration effect to bacteria biomass on production of biopesticides. The first step of this research is cultivation of medium test. The second step is preparation of inoculums using TSA (Tryptic soybean agar) and TSB (Tryptic soybean broth). After that the inoculums are cultivated on tofu waste substrate using bubble column bioreactor with aeration of 0,5, 1, 1,5 vvm. The parameters from this research are pH, OD (optical density), bacteria biomass dry weight, and residual sugar. The last step is toxicity test to nematode P. brachyurus. Completely randomized factorial design test with aeration as factor is used in this research The result showed that tofu waste can be used as substrate to P. putida growth to produce biopesticides. The highest biomass dry weight is 1,608 g/l which is obtained from cultivation with 1 vvm aeration after 36 hours and the lowest is 1,191 g/l from 0,5 vvm. The toxicity test of nematode P. brachyurus showed that the most effective treatment is using aeration 1 vvm. The percentage of nematode mortalitas is about 99%.
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Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular