Caister Academic Press

Fructan Biosynthesis in Bacteria

Lázaro Hernández, Yamira Quintero and Alexis Musacchio
from: Microbial Exopolysaccharides: Current Research and Developments (Edited by: Özlem Ateş Duru). Caister Academic Press, U.K. (2019) Pages: 133-164.

Abstract

In nature, fructans are synthesized from sucrose by a relative low number of plant species and a wide range of microorganisms, including bacteria, archaea, and fungi. Levan, the predominant bacterial fructose polymer, is a biofilm-forming exopolysaccharide that fulfills diverse biological roles. The biosynthetic enzyme levansucrase (EC 2.4.1.10) catalyzes sucrose hydrolysis, sucrose fructosylation, and fructan polymerization, as the three main activities. The hydrolase/transferase ratio, the spectrum of fructan products, and the overall levan yield vary depending on the intrinsic properties of each enzyme and the reaction conditions. This review provides a detailed update on the most relevant genetic, biochemical, structural, and evolutionary aspects of levansucrase. Several levan-producing bacteria are enzymatically equipped to utilize the polymer as an alternative carbon source under starving conditions. The last section describes how the strictly controlled transcription of levanase genes ensures the prevalence of levan synthesis over degradation whenever exogenous sucrose is available as an energetic substrate read more ...
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