Dextran: Sources, Structures, and Properties

Elsa Díaz-Montes

doi:10.3390/polysaccharides2030033

Abstract

Dextran is an exopolysaccharide (EPS) synthesized by lactic acid bacteria (LAB) or their enzymes in the presence of sucrose. Dextran is composed of a linear chain of d-glucoses linked by α-(1→6) bonds, with possible branches of d-glucoses linked by α-(1→4), α-(1→3), or α-(1→2) bonds, which can be low (<40 kDa) or high molecular weight (>40 kDa). The characteristics of dextran in terms of molecular weight and branches depend on the producing strain, so there is a great variety in its properties. Dextran has commercial interest because its solubility, viscosity, and thermal and rheological properties allow it to be used in food, pharmaceutical, and research areas. The aim of this review article is to compile the latest research (in the past decade) using LAB to synthesize high or low molecular weight dextran. In addition, studies using modified enzymes to produce dextran with specific structural characteristics (molecular weights and branches) are addressed. On the other hand, special attention is paid to LAB extracted from unconventional sources to expose their capacities as dextran producers and their possible application to compete with the only commercial strain (Leuconostoc mesenteroides NRRL B512).

Highlights

Lactic acid bacteria (LAB) are microorganisms that produce lactic acid as the main or only product of carbohydrate fermentation
LAB are considered probiotic bacteria because they can be incorporated into food to improve the consumer0 s intestinal microbial balance, and they are generally recognized as safe (GRAS) because they are not pathogenic for humans [3]
The production of dextran occurs mainly by a fermentation with LAB in a medium with sucrose; the enzymatic route has been used because it is a direct method in which other products or metabolites are not produced

Summary

Introduction

Lactic acid bacteria (LAB) are microorganisms that produce lactic acid as the main or only product of carbohydrate fermentation (heterofermentation or homofermentation, respectively). Levan and inulin are the fructans produced by LAB, while the most commonly produced glucans are cellulose, pullulan, curdlan, mutan, alternan, and dextran [6]. These natural polysaccharides have been used as carriers, encapsulants, thickeners, binders, lubricants, and additives in the pharmaceutical and food industries [7]. Polysaccharides 2021, 2, Polysaccharides 2021, 2 the most important EPS for medical and industrial use is dextran, which was initially believed to be synthesized only by Leuconostoc mesenteroides, but subsequent research reported dextran, which by wasanother initially believed be Section synthesized.

Synthesis of Dextran

Characteristics

Properties of Dextran

Concluding Remarks and Future Perspectives