Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Isolation and Molecular Characterization of Lactic Acid Bacteria From Raw Milk(Izmir Institute of Technology, 2002) Çetin, Ali Emrah; Yenidünya, Ali Fazıl; Yenidünya, Ali Fazıl; 04.03. Department of Molecular Biology and Genetics; 04. Faculty of Science; 01. Izmir Institute of TechnologyLactic acid bacteria are industrially important because they are used as starter cultures in food production, they produce antimicrobial compounds and they are used in the formulation of probiotic products. Several dairy products such as raw milk, traditionally fermented cheese (produced without the use of commercial starter cultures), and kefir which are produced in country are good sources of novel lactic acid bacterial strains. These lactic acid bacterial strains may have potential for the production of new fermented dairy products with characteristic aroma and flavour. Therefore, the isolation of lactic acid bacteria from natural products and their identification are important. For many years, several phenotypic methods have been used to identify lactic acid bacteria, but they are not often capable of effectively differentiating subspecies and strains within a genus. New methods based on the genotypic properties have been developed and used for the proper classification of bacteria The aim of this research was the isolation of lactic acid bacteria from raw milk and the identification of the lactic acid bacterial isolates by biochemical tests, polymerase chain reaction (PCR)-based methods and pulsed field gel electrophoresis (PFGE). Lactic acid bacteria were isolated from cow.s raw milk and identified by biochemical reactions. Two PCR based methods, ITS-PCR (Internal Transcribed Spacer-PCR) and PCR-RFLP (PCR- Restriction Fragment Length Polymorphism) were then used for the differentiation of reference strains of lactic acid bacteria. PCR-RFLP method, based on the amplification and restriction digestion of 16S rRNA gene, was found to be useful for the identification. Thirteen raw milk isolates were identified as Lactococcus lactis, 24 as Enterococcus spp., and 2 as Lactococcus lactis subsp. cremoris by PCR-RFLP method. Pulsed field gel electrophoresis was also optimized for the identification of reference strains. Restriction profiles obtained by digesting the genomic DNA with Sma I enabled differentiation of the reference strains of Lactococcus, Enterococcus, and Streptococus thermophilus.Master Thesis Determination of Antibiotics in Raw and Uht Milk Samples by the Image Forming Method of Biocrystallization(Izmir Institute of Technology, 2011) Pelvan, Merve; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThis study aims to investigate a new technique for the antibiotic residue analysis that can able to detect a wide range of antibiotic residues directly in raw and drinking milk by producing reliable and definitive results. "Biocrystallization method" was selected as a new technique to distinguish the raw and UHT milk samples containing antibiotic residues from the antibiotic free ones. This method is based on the crystallographic phenomenon that occurs after adding ionic substances to an aqueous solution of dihydrate CuCl2 and drying in a constant temperature and relative humidity. In this study, the raw and UHT milk samples was screened for antibiotic residues using New SNAP* Beta-Lactam (IDEXX Lab. USA) test kits. Then, the chemical properties of milk samples (e.g. fat%, protein%, lactose%, minerals%, SNF%) were determined. At the same time, biocrystallization method were optimized with antibiotic free raw milk samples. Evaluation of biocrystallograms was performed via a panel. The best biocrystallogram images were obtained for 6 ml of milk samples prepared from 0.5 % milk and 5% CuCl2.2H2O solution by mixing at a ratio of 3 (milk) to 1 (CuCl2.2H2O) dried at 30 °C ,60% relative humidity for 22 h. After optimization, the raw and UHT milk samples were spiked with Penicillin G (2, 4, 8 ppb) and Ampicillin (2, 4, 8 ppb) to generate biocrystallogram images at the optimized conditions. All the images were evaluated with a visual inspection. Biocrystallization method was successfully used to distinguish raw and UHT milk from the samples spiked with Penicillin G and Ampicillin. This method gave better results when discriminating naturally contaminated raw milk from antibiotic free raw milk.