Studies on dextransucrase production by Streptococcus sanguis 804, NCTC 10904: An examination of dextransucrase production patterns at varius pH values and the dextrans elaborated

Black, Phyllis Margaret (1975) Studies on dextransucrase production by Streptococcus sanguis 804, NCTC 10904: An examination of dextransucrase production patterns at varius pH values and the dextrans elaborated. PhD thesis, University of Glasgow.

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Abstract

Streptococcus sancuis 804 is a microaerophic organism which was originally isolated from human dental plaque (Carlsson, 1965). It is one of the first organisms to colonise the tooth surface during dental plaque formation and is the predominant aerobic streptococcus in young plaque (Carlsson, 1965). It produces the constitutive, extracellular enzyme, alpha-(1,6)glucan: D-Fructose 2-glucosyltransferase (EC 2.4.1.5), commonly known as dextransucrase, which polymsrises the glucose moiety of sucrosetoform dextran, with the release of fructose. The dextran it produces is believed to contribute to dental plaque formation and the initiation of dental caries. This study examined dextransucrase production by S. sanguis at different pH values in order to elucidate optimal conditions for its production. The optimum pH was found to be in the region of 7-1 +/- 0-1 but, it emerged, that at all pH values studied the enzyme was produced in three, distinct, reproducible phases. Dextran was prepared from enzyme harvested at each of the three phases at pH 7-1 +/- 0-1 and, after characterisation of the substances as dextran by gas-liquid chromatography, acidic hydrolysis and a specific aggregation technique, they were examined for structural differences by infrared spectroscopy, periodate exidation and enzymic degradation. The results suggest that the three preparations differ in structure. Crude enzyme prepared from culture supernatant at the second or third peak of enzyme activity was partially purified by hydroxylapatite chromatography. Enzyme from the second peak had a pH optimum in the region 5-2 - 7-5. It is suggested that there may be more than one enzyme involved in dextran production by S.sanguis 804.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J A Beeley
Keywords: Microbiology
Date of Award: 1975
Depositing User: Enlighten Team
Unique ID: glathesis:1975-73710
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: http://theses.gla.ac.uk/id/eprint/73710

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