Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Xylan Degradation Mechanism of Human Intestinal Bacteria(Izmir Institute of Technology, 2017) Polat, Nüket; Büyükkileci, Ali Oğuz; Güleç, ŞükrüXylan is the second most abundant plant cell wall polysaccharide after cellulose. The xylan rich lignocellulosic material obtained from agriculture, forestry and industrial wastes provides cost effective raw materials. The degradation of xylan in the human body is an important process contributing to the continuation of the microbial communities living in the human colonic ecosystem. Due to its complex, long chain structure and the various chemical bonds it contains, xylan hydrolysis requires different enzymatic activities. Bacteria that live in the colon and are useful for human health, such as Bifidobacterium and Lactobacillus species can not perform xylan utilization. However, several types of xylan are utilized by the Bacteroides species, which have the second largest density in the colon. In this study, different Bifidabacterium and Bacteriodes species were investigated for their ability to degrade beechwood xylan and corncob xylan. Bifidabacterium and Bacteriodes were cultured together in tubes containing xylan as the sole carbon source. It was observed that; the B. animalis subsp. lactis, which does not have the ability to use the xylan, could grow when cultured on xylan-containing medium with Bacteroides species. These showed that, the xylan in the media was degraded into xylooligosaccharides by the Bacteroides species and the XOS formed was used as a carbon source by both species. The short chain fatty acid and lactic and succinic acid production profiles of co-cultures were different than the mono cultures, indicating a positive effect of co-culturing. This study showed that xylan is a potential prebiotic carbohydrate, which can selectively stimulate the growth of beneficial bacteria in the colon, as a result of possible cross feeding of different bacteria residing in the colon.Master Thesis Real-Time Pcr as a Molecular Tool for the Enumeration of Probiotics in Commercial Products(Izmir Institute of Technology, 2016) Öz, Ödül; Baysal, Ayşe Handan; Arslanoğlu, AlperQuantitative Real-Time PCR (qPCR) assays targeting the 16S rDNA was developed as a genus and species specific detection tool for Bifidobacterium and Lactobacillus, and Bifidobacterium animalis subsp. lactis BB-12 and Lactobacillus acidophilus LA-5, respectively. Standard curves were established to quantify these probiotic bacteria. The linear regression of standard curves indicated high correlations between the log numbers of pure probiotic culture cells and the Ct values. The assay had a high efficiency and the limit of detection was estimated to be 1.54 ng DNA (corresponding to 104 cells). Results show that qPCR method may be very useful as a rapid, sensitive and specific tool for detecting and quantifying B. animalis subsp. lactis BB-12 and L. acidophilus LA-5 in probiotic supplements. FTIR spectroscopy was used for the first time to determine the ratios of different microorganisms in commercial probiotic supplements. FTIR analysis was also performed for the pure probiotic cultures of B. animalis subsp. lactis BB-12 and L. acidophilus LA-5. Results obtained in this study showed that FTIR spectroscopy is potentially a rapid method for determining probiotic cell components and their ratios in the supplements and verification their detection and identification.Master Thesis Production of B-Galactosidase Using Lactic Acid Bacteria and Optimisation of Fermentation Parametters(Izmir Institute of Technology, 2007) Üstok, Fatma Işık; Tari, CananFood grade thermostable B -galactosidase preparations are always in demand for a number of industrial applications. Thermostable -galactosidases from LAB having a neutral pH-optimum can be safely used to reduce the lactose content of milk for the lactose intolerant people. In this study, -galactosidase was produced with high productivities by novel Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains isolated from traditional Turkish yogurt samples in Toros mountain region. A full factorial statistical design was used separately for Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains in screening experiments. Among the strains, Lactobacillus delbrueckii subsp. bulgaricus 77 and Streptococcus thermophilus 95/2 were found to have high potential for B-galactosidase and lactic acid production, therefore these were used in the further optimisation studies.The efficiency of different cell disruption methods was investigated on the extraction of -galactosidase. Among these, lysozyme enzyme treatment was determined as the most effective method. Optimisation studies were carried out using response surface methodology to optimize fermentation conditions for pure strains as well as for mixed ones. Therefore, symbiotic relationship between St 95/2 and Lb 77 were investigated as well. Symbiotic relationship provided 39% and 6.1 % more -galactosidase activity and 44 % and 9.73 % more lactic acid production when compared to the optimisation results of pure strains Lb 77 and St 95/2, respectively.Overall, characterization studies showed that enzymes obtained from these strains can be considered as food grade and thermostable since they are obtained from thermophile, food originated novel LAB of local microflora.