36B-11 |
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P. BASARAN, Dept. of Food Engineering, Suleyman Demirel Univ., Cunur Kampusu, Isparta, 32260, Turkey and N. Basaran, Food Science & Technology, Cornell Univ., New York State Agricultural Experiment Station, 630 W. North St., Geneva, NY 14456-1371. Lactococcus lactis is a Gram-positive lactic acid bacterium (LAB) that is widely used as starter cultures in the dairy industry for production and preservation of fermented foods. D-xylose is the second most commonly found sugar in the environment. D-xylose is converted to D-xylulose by xylose isomerase enzyme. Xylulose is subsequently phosphorylated with xylulokinase (XK) to xylulose-5-phosphate, which can be further catabolized via the pentose phosphate and the Embden–Meyerhof–Parnas (EMP) pathways to pyruvate. Xylose isomerase enzyme also catalyzes the conversion of D-glucose to D-fructose and is used as biocatalyzer for the production of high fructose corn syrup in food industry. Our main objective was to examine the presence of genes for xylose catabolism in LAB. Nine environmental and seventeen commercial isolates identified by conventional physiological and biochemical tests as LAB were used for screening. A set of primers and DIG-dUTP labeled functional probes were developed for the detection of xylose isomerase gene (xylA) and xylulose kinase (xylB) gene fragments of LAB. Total chrosomal DNA was isolated from cultures and digested with BamHI-HindIII restriction endonucleases. Digested chromosomal DNA was used in Southern Blot Hybridization. The set of oligonucleotides and probes allowed detection of xylA and xylB gene fragments in all the Lactococcus strains except two. Neverthless, neither of the strains tested did show xylose isomerase or xylulokinase enzymatic activities. Xylose catabolism has great commercial significance in the fermentation of wood waste and fibre. LAB perhaps the safest and most effective microorganisms for fermenting sugars. The implications for the presence of the genes encoding for xylose catabolism in LAB provide clues about the possible evolution of genes as they loose their physiological importance.
Session 36B, Biotechnology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |