The science of today is the technology
is a linear polysaccharide made of many glucose molecules joined as chains of varying length. It was the first industrial polysaccharide produced by lactic acid bacteria (LAB) and is also one of the first water soluble gums known to man. Additionally, dextran is one of the first microbial polysaccharides to be commercialised and to be approved for use in food.
The Dextran polysaccharide chain is lengthened using the enzyme dextran sucrose, which sequentially adds glucose units to the molecule chain. The biosynthesis of dextran has been demonstrated in numerous bacteria, especially in Streptococcus mutans, Leuconostoc mesenteroides ssp. mesenteroides and Leuconostoc mesenteroides ssp. dextranicum. Leuconostoc produces the enzyme dextran sucrase and secretes it into the culture medium in the presence of sucrose. This enzyme, dextran sucrase, then synthesises dextran from the sucrose substrate. Dextran is an extremely versatile compound and it wide potential uses are favoured by the different properties of the polymer such as; (i) neutral and water soluble, (ii) stable for more than 5 yr., (iii) biocompatibile: Dextran can be safely consumed and (iv) is biodegradable.
A fragment of the dextran structure is shown in figure 1.
In the 1940s, Allene Jeanes was a scientist at the USA's Northern Regional Research Laboratory. A soft drink company had sent her a sample of their product, which had mysteriously become thick and gooey. She soon found that a bacterium had converted the sugar in the soda to dextran. Perhaps the bacteria had come from some worker's dental plaque! She found that the bacterium could be grown in the lab in a vat of sugar solution, and make lots of dextran. During World War II, doctors tried transfusing plasma which is blood without any cells in it. It does not cause complications, and can immediately increase the blood pressure and replenish electrolytes. However, plasma can spoil easily, so it must be kept on ice all the time. In the battlefield, where do you store plasma? That's where dextran helps. It can be carried dry, quickly mixed with water and salt and transfused to the patient. It pushes up the blood pressure immediately, while the saline helps restores some electrolytes. Dextran was then purified, dried, and sent to Korea. There it would help soldiers survive the journey from battlefield to hospital, where they could be treated further.