New bacterial strain may produce higher yield dextran, suggests research

By Nathan Gray

- Last updated on GMT

Related tags Lactic acid bacteria Bacteria Microbiology

A newly identified lactic acid bacteria strain that produces higher yields of dextran than other strains has been identified by researchers.

Writing in the journal Carbohydrate Polymers​ researchers from The Karachi Institute of Biotechnology & Genetic Engineering (KIBGE) in Pakistan reported that detxtran – a food additive often used as a thickener or stabiliser – produced by the lactic acid bacteria Leuconostoc mesenteroidesAA1 ​is of higher molecular weight and yield than current commercially available strains.

“The key points for production of dextran in industry are its molecular weight and dextran yield and keeping these point in view​L. mesenteroidesAA1 is a potential candidate for dextran production at industrial scale,”​ said the researchers, led by Shah Ali Ul Qader from​KIBGE.

“Commercially​L. mesenteroidesB-512F is used for the production of dextran and the percent conversion of sucrose to dextran by this strain is reported to be 41.0%, as compared to​L. mesenteroidesAA1 which is 48.9%,”​ they added.


Long-chain, high-molecular-weight polymers that dissolve or disperse in water to give improved rheological (gelling, thickening) or physico-chemical (emulsion stabilisation, particle suspension etc) properties, are important tools for food product formulation.

Most of such polysaccharides currently used are obtained from plants and seaweed – including starch, pectin, agar and alginates – however microbial fermentation is also used for the production of food polysaccharides including homo-polymers of glucose – such as beta-glucans, bacterial cellulose, pullulan – and hetero-polymers – like xanthan gum, gellan gum, bacterial alginates. Dextran belongs to this group of homopolysaccharides.

Ul Qader and colleagues noted that an “incredible increase in the demand of biodegradable biotechnological products including enzymes and biopolymers” ​such as​food polysaccharides has diverted research to search for more biological sources capable of producing them at industrial scale.

They added that many microbial sources have been exploited for this purpose, noting that one of the most important microbial sources are the lactic acid bacteria, which have been popular for producing polysaccharides due to its generally regarded as safe status (GRAS) and their history of use in the food industry.

Bacterial production

“Among many exopolysaccharides available from microbial sources dextran has gained worldwide recognition because ​L. mesenteroidesis capable of producing water soluble and insoluble dextran with diversified properties,”​ said the researchers.

As a result, they said, L. mesenteroides​ is used for the production of dextran that has several targeted industrial applications from food, cosmetics, and pharmaceuticals. However, they added that with the rapid advances in enzymology and fermentation technology, the search for new strains able to produce commercially feasible quantities of dextran is continuous.

Study details

Ul Qader and co-workers reported that the yield of dextran and it molecular weight from L. mesenteroidesAA1​ to be higher than in previously reported strains.

They said that the physicochemical characteristics and structural analysis of dextran from L. mesenteroidesAA1​ revealed that it has many potential applications in industry, noting that L​. mesenteroidesAA1​ can be used for commercial production of dextran on large scale.

“The dextran produced by L. mesenteroides AA1 has remarkable potential to be used for several industrial purposes,” ​they added – noting that dextran produced by L. mesenteroides​ AA1 is water soluble and tasteless.

Source: Carbohydrate Polymers
Published online ahead of print, doi: 10.1016/j.carbpol.2011.08.094
“Characterization and potential applications of high molecular weight dextran produced by Leuconostoc mesenteroides AA1”
Authors: A. Aman, N.N. Siddiqui, S.A.U. Qader

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