Judul: Mekanisme Antimikroba Plantaricin dari Lactobacillus plantarum IIA-1A5 Asal Daging Sapi Lokal terhadap Staphylococcus aureus.
Abstrak: Plantaricin IIA-1A5 is a peptide compound produced by Lactobacillus plantarum IIA-1A5 lactic acid bacteria displaying antimicrobial activities. The purpose of this study is to analyze the mode of action of plantaricin and Staphylococcus aureus disruption by plantaricin IIA-1A5 through testing antimicrobial activities. Results showed the molecular weight of plantaricin IIA- 1A5 was 6.41 kDa. Based on the antagonistic test using paper disc method, plantaricin IIA-1A5 have the diameter of growth inhibition zone to S. aureus larger than that of control (P<0.05). Ability of plantaricin IIA-1A5 to distrupt cell membrane same as triton X-100, but better than that of ethanol, chloroform, methanol, hexana, and SDS (P<0.05). Based on cell leakage test, S. aureus suspension treated with plantaricin displayed higher absorbance value compared to that of controls (P<0.05). SEM analysis showed remarkable cell leakage of S. aureus by plantaricin IIA-1A5.
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Judul: Stability and Antimicrobial Activity of Plantaricin Produced by Lactobacillus plantarum at Alkaline pH
Abstrak: Plantaricin produced by L. plantarum is known to display an adaptive response to alkali stress that enhances its capacity to more effectively stable at alkali condition. The aim of the research was to examine the stability of plantaricin produced by L. plantarum 1A5, 1B1, 2B2 and 2C12 and its antimicrobial activity at alkaline pH. The experiment was done based on completely randomized design (CRD) with factorial arrangement 2 x 4, two levels of pH value and four levels of L. plantarum strains in three replications. Variables analyzed were protein concentration, inhibition zone of the antagonistic test was assayed by agar well diffusion and antimicrobial activity of plantaricin against indicator bacteria at alkaline pH. Plantaricin was found to be sensitive to alkaline treatment. No interaction between pH and strains of L. plantarum to antimicrobial activity of plantaricin (P>0.05). Plantaricin showed antimicrobial activity against Gram positif and Gram negatif bacteria including S. typhimurium ATCC 14028, S. aureus ATCC 25923, E. coli ATCC 25922, P. aeruginosa ATCC 27853 and B. cereus. Plantaricin produced by L. plantarum 1A5, 1B1, 2B2 and 2C12 was stable at alkaline pH but the stability of plantaricin decreased because of alkaline treatment to S. typhimurium ATCC 14028 (P<0.01). Stability of plantaricin after alkaline treatment showed plantaricin potentially could be used as biopreservative on alkali products.
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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