Judul: Evaluasi Kemampuan Lactobacillus rhamnosus R21 Asal Air Susu Ibu untuk Berkompetisi dengan Salmonella Typhimurium selama Rekonstitusi Susu Formula Bayi
Abstrak: Numerous studies have shown that lactic acid bacteria (LAB) may provide health benefits if they live in human gastrointestinal track at a sufficient amount. This fact encourages the development of the use of LAB as probiotic in food products, for example in powdered infant formula. The aim of the present study was to evaluate the ability of L. rhamnosus R21 to compete with one of pathogenic bacteria that commonly contaminate powdered infant formula, namely Salmonella Typhimurium. Lactic acid bacteria used in this study was isolated from breast milk, namely Lactobacillus rhamnosus R21. In addition, this study may indicate the effect of reconstitution temperature towards bacterial competition. Competition between L. rhamnosus R21 and S. Typhimurium was tested by measuring viability after reconstitution at 27, 60, and 70 oC and the growth of both bacteria during hang time of 0, 2, 4, 6, and 8 hours. The doses of L. rhamnosus R21 used in this study were 109, 108, and 106 CFU/mL. These bacteria competed with 104 CFU/mL of S.Typhimurium at three different reconstitution temperatures: 27, 60, and 70 °C. The results showed that L. rhamnosus R21 was more resistant to reconstitution temperature of 60 and 70 oC than S. Typhimurium.Competition between both bacteria showed that an amount of 109 CFU/mL L. rhamnosus R21 was able to inhibit the growth of S. Typhimurium in reconstituted infant formula for 8 hours of hang time. The inhibition values are 3.84 log CFU/mL (27°C), 3.96 log CFU/mL (60 °C), and 3.16 log CFU/mL (70 °C). While, an amount of 108 and 106 CFU/mL L. rhamnosus R21 performed less inhibition to S. Typhimurium. The ability of L. rhamnosus R21 to lower the pH value by producing lactic acid has important role in competition with S. Typhimurium. While the reconstitution temperature did not significantly affect the competition between both bacteria.
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Judul: Kemampuan Campuran Bakteri Asam Laktat Kandidat Probiotik Asal Air Susu Ibu Berkompetisi dengan Cronobacter sakazakii pada Susu Formula Rekonstitusi
Abstrak: Cronobacter sakazakii is an emerging pathogen occasionally found in powdered infant formula (PIF) and causes ilnessess in certain groups of infants. To achieve the minimum risk level of C. sakazakii it is recommended to carry on reconstitution of PIF at temperature of 70 °C or more. The recommended temperature may therefore influence the presence of lactic acid bacteria (LAB) commonly added as probiotic in PIF and other milk powder. The objectives of this study were to determine the antimicrobial activities of cocktail of L. rhamnosus isolated from breast milk against C. sakazakii, to evaluate the effect of the reconstitution temperature towards the survival and growth of L. rhamnosus and C. sakazakii, and to determine the influence of L. rhamnosus on the growth of C. sakazakii after reconstitution. L. rhamnosus cocktail was more effective in inhibiting the growth of single strain C. sakazakii than cocktail of C. sakazakii. The use of cocktail of L. rhamnosus R21 & R25 could inhibit the growth of C. sakazakii YR c3a by 3.75 log CFU/mL. At the same time, the growth of cocktail of L. rhamnosus was not affected by the presence of C. sakazakii. Addition of cocktail of L. rhamnosus R21 & R25 in reconstituted powdered infant formula did not influence the growth of C. sakazakii significantly. Survival of C. sakazakii was influenced by reconstitution temperatures.
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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