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: Sintas Bakteri Asam Laktat Kandidat Probiotik Kering Beku Asal Air Susu Ibu Selama Rekonstitusi dan Kemampuannya untuk Berkompetisi dengan Cronobacter sakazakii
Abstrak: Powdered infant formula (PIF) is a fabricated food product whose nutrition is formulated to correspond to breast milk. Nowadays, some PIF manufacturers have supplemented PIF with probiotic bacteria. However, due to possible Cronobacter spp. contamination, reconstitution at 70 oC is adviced thus it may also affect the viability of lactic acid bacteria (LAB). The objective of this study was to evaluate the survival of freeze dried LAB isolated from breast milk during reconstitution and their ability to compete with Cronobacter sakazakii (C. sakazakii) in PIF. This study was conducted in 4 stages, i.e. (1) screening of LAB isolates based on the survival during reconstitution at 50 oC; (2) competition of LAB isolates with C. sakazakii YRC3a; (3) evaluation of the LAB isolates on freeze drying process; and (4) competition of LAB isolates with C. sakazakii YRC3a in PIF at various reconstitution temperatures. Screening of LAB showed that all LAB isolates decreased in cell number after reconstitution at 50 oC. Based on the result of screening, 4 LABs were chosen i.e Lactobacillus rhamnosus (L. rhamnosus) R14, R21, R23, and R25 because the bacterial number decrease was lower. However, only L. rhamnosus R21 and R25 were capable of inhibiting the growth of C. sakazakii YRC3a. Meanwhile, assessment of the LAB survival during freeze drying process showed insignificant reduction of cell number of L. rhamnosus R21 and R25. Competition of freeze dried L. rhamnosus R21 and R25 with C. sakazakii YRC3a during reconstitution in PIF at various reconstitution temperatures (50, 60, and 70 oC) showed that the freeze dried LAB were able to suppress the number of C. sakazakii YRC3a as the temperature increased. The result also showed that LAB isolates did not undergo significant cell reduction as the reconstitution temperature increased.
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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