Abstract
Streptococcal mutans synthesized under different conditions by growing cultures or by their glucosyltransferases were shown to exhibit a great structural and property diversity. Culturing and environmental factors causing structural differences in mutans were specified. All of the obtained biopolymers (76 samples) were water-insoluble and most of them (72) had a structure with a predominance of α-(1→3)-linked glucose (i.e., the content of α-(1→3)-linkages in the glucan was always higher than 50%, but did not exceed 76%). An exception were four glucans containing more than 50% of α-(1→6)-sequences. In these structurally unique mutans, the ratio of α-(1→3)- to α-(1→6)-bonds ranged from 0.75 to 0.97. Aside from one polymer, all others had a heavily branched structures and differed in the number of α-(1→3), α-(1→6), and α-(1→3,6) linkages and their mutual proportion. The induction of mutanase production in shaken flask cultures of Trichoderma harzianum by the structurally diverse mutans resulted in enzyme activities ranging from 0.144 to 1.051 U/mL. No statistical correlation was found between the total percentage content of α-(1→3)-linkages in the α-glucan and mutanase activity. Thus, despite biosynthetic differences causing structural variation in the mutans, it did not matter which mutan structures were used to induce mutanase production.
Highlights
Mutans, i.e., mixed-linkage [α-(1→3), α-(1→6)] water-insoluble D-glucans, are structural and functional components of cariogenic biofilms and are commonly used as specific and efficient inducers of mutan-degrading enzymes known as mutanases—α-(1→3)-glucan 3-glucanohydrolases [1]
A detailed chemical structure of a mutan synthesized by cariogenic streptococci was analyzed, and the best operating conditions for efficient production of this polymer were standardized [7,16]
It was assumed that each deviation from optimal conditions estimated for both stages of mutan production can modify the mutual proportions of the different types of links in the polymer leading to a high structural diversity of the glucans obtained in this way
Summary
I.e., mixed-linkage [α-(1→3), α-(1→6)] water-insoluble D-glucans, are structural and functional components of cariogenic biofilms and are commonly used as specific and efficient inducers of mutan-degrading enzymes known as mutanases—α-(1→3)-glucan 3-glucanohydrolases [1]. The investigation of the structural diversity of mutans synthesized under changing culture and environmental conditions and the estimation of the effect of these diverse inducers on mutanase activity would facilitate the production of this valuable enzyme. Data from in vitro studies using individual Gtfs indicate that the polymers synthesized possess a distinct structure and properties than the products formed by a mixture of Gtfs or a crude enzyme preparation [13,17,18]. The aim of these investigations was to show structural variations in streptococcal mutans caused by their synthesis under different culture and environmental conditions, and to study the influence of structurally diverse biopolymers on the induction of synthesis of T. harzianum mutanase
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