Judul: The Occurrence of Genes for Folate Production in Local Isolates of Lactic Acid Bacteria and Distribution of Extracellular and Intracellular Folates
Abstrak: Folate-producing lactic acid bacteria (LAB) can act as folate-efficient producers or overproducers. Folate-efficient bacteria will only produce folate as their needs and only if folate is not available in the medium, whereas folate-overproducing bacteria can produce folate beyond their needs, even though there is early folate in the medium. However, a microorganism must have an efficient metabolic system; hence, finding folate-overproducing bacteria might be challenging. This work aimed to determine key genes for folate production and obtain folate-producing LAB. In particular, the objectives of this research were: (1) mapping the folate biosynthesis genes in diverse LAB species and identifying their role in the ability of LAB to produce folate; (2) finding potential folate biosynthesis marker genes in the genotypic screening for folate producers; (3) identifying the types of folate and the distribution of intra- and extracellular folate; and (4) applying stress exposure to methotrexate (a folate analogue) and the addition of enhancer compounds (PABA, glutamate, PABA-glutamate, CaCl2, and ascorbic acid) for effectively increasing extracellular folate production in LAB. Of 13 LAB isolates from Indonesian fermented foods (tempeh, tapai, fermented mustard, kefir granules) and breast milk, eleven isolates had all of the eight genes involved in folate biosynthesis (folE, folQ, folB, folK, folP, folC1, folA, and folC2) and could produce extracellular folate (ranging from 10.37 to 31.10 µg/mL). In contrast, two LAB isolates lacked several folate biosynthesis genes (folQ, folP, and folA) and could not produce extracellular folate. The folQ gene, which was not found in non-folate-producing isolates, could potentially be used as a marker for folate biosynthesis. Phylogenetic tree analysis showed that the folate biosynthesis genes (except folK and folP) of the LAB isolates in this study were on the same branch as the folate biosynthesis genes of the various LAB isolates from the database, supported by a higher percentage of conserved sites than the variable sites. The folK and folP genes may be non-essential genes in the folate biosynthesis pathway, and further research is needed to study their contribution level to de novo folate biosynthesis. Production of extracellular folate by selected LAB isolates was further evaluated in folate-free media and analyzed using the HPLC-DAD method with three individual-form folate standards, i.e., tetrahydrofolate (THF), 5-methyl-tetrahydrofolate (5-MTHF), and folic acid. Although the three folate standards could be detected with good peak separation, only the 5-MTHF peak was detected in extracellular folate samples of LAB isolates. Another peak that was only found in samples of folate-producing isolates was also suspected to be a folate peak and had a much higher area than the 5-MTHF peak, and further quantified as other folates, although further analysis is needed to confirm the form of folate. Five LAB isolates (R23, JK13, BK27, S2SR08, and NG64) produced 10% of 5-MTHF, while the other 7 LAB isolates (4C261, R12, R15, BD2, JK16, BG7), which included the reference strain (WCFS1), produced a 5-MTHF content of only 6%, and the rest are other folates. The highest extracellular folate producer isolates, namely Lacticaseibacillus rhamnosus R23 from ASI and Limosilactobacillus fermentum JK13 from kefir granules produced a much higher proportion of extracellular folate (95%)
Keyword: lactic acid bacteria, biosynthesis, distribution, folate, production, strategy

Judul: Characterization of indigenous lactic acid bacteria from beef as probiotic and identification by 16s rRNA gene sequencing
Abstrak: Functional foods are foods that have health promising benefit over and above their basic nutritional value. Probiotics are included as component of functional foods. Probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host. The research was aimed to characterize the probiotic properties and to identify indigenous lactic acid bacteria (LAB) isolated from fresh beef derived from traditional market around Bogor, West Java, Indonesia. The twenty eight LAB isolates showed different ability to survive under simulated gastrointestinal conditions. Only 10 isolates could survive well at pH 2.0 (survival rate over than 50%) and the population increased at pH 2.5, 3.2 and 7.2. The ten LAB isolates (strain 2B4, 1B1, 1A5, 2C2, 2D1, 2B2, 1C4, 2B1, 1A32 and 2C12) could survive well at 0.5% bile salt, showed antibacterial activities and good coagregation capabilities against the tested pathogenic bacteria (Escherichia coli ATCC 25922, Salmonella Typhimurium ATCC 14028, Enteropathogenic Escherichia coli/EPEC, and Staphylococcus aureus ATCC 25923) and could adhere to intestinal surface by in vitro analysis. The 16S rRNA gene could be amplified by PCR (Polymerase Chain Reaction) to get single band with designed primer. Identification by 16S rRNA gene sequencing of 20 isolates showed that 11 isolates were identified as Lactobacillus plantarum, 6 isolates as Lactobacillus acidophilus, 2 isolates as Pediococcus pentosaceous and 1 isolate as Enterococcus faecium. The ten LAB isolates were proven to be probiotic candidates, which consist of 7 isolates of Lactobacillus plantarum (strain 1B1, 1A5, 2D1, 2B2, 1C4, 2B1, 2C12) and 3 isolates of Lactobacillus acidophilus (strain 2B4, 2C2, 1A32). Lactobacillus plantarum 2C12 and Lactobacillus acidophilus 2B4 were further evaluated to prevent diarrheae caused by EPEC. Albino rats (Rattus norvegicus) were daily orally administered by 108 cfu/ml of both probiotics without or simultaneously infected with EPEC (106 cfu/ml). Negative control was not infected by probiotic and EPEC while positive control was challenged with EPEC alone. It was observed that rats administered by L. plantarum 2C12 and L. acidophilus 2B4 which were challenged with EPEC had better performances when compared with the positive control for daily weight gain, feed consumption and feed efficiency rate. Both probiotics could prevent diarrhea caused by EPEC by increasing total population of lactic acid bacteria 1 log cfu/cm2 on mucosa of cecum and 1 log cfu/g on content of cecum, reducing population of E.coli 1-2 log cfu/cm2 on mucosa of cecum and 1 log cfu/g on cecum content also increasing 33.66-71.79 x 106 cell on lymphocytes. L. acidophilus 2B4 had better probiotic characteristics than L. plantarum 2C12, with specific health function to prevent diarrhea caused by EPEC.
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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