Dextransucrases are glucosyltransferases that catalyze the transfer of alpha-D-glucopyranose residues from sucrose to low molecular weight acceptors, forming oligos and polysaccharides. The main dextransucrase reaction product is dextran, along with the release of fructose. Dextran is a linear polymer of glucose joined mainly by alpha (1 -> 6) links and fewer alpha (1 -> 2),alpha (1 -> 3) and/or. alpha (1 -> 4) links. The structural characteristics or the frequency and type of linkage in dextran are dependent on the nature of the enzyme and type of producing microorganism. It has acknowledgeable industrial applications in medical, pharmaceutical, food, textile and chemical industries, depending on its structural characteristics. This paper offers the physical and chemical characterization of a clinically important dextran produced by dextransucrase of a newly isolated strain of L. lactis KU665298 in a laboratory fermenter. Structural analysis of dextran by FTIR, H-1 NMR, C-13 NMR confirmed the presence of a large percentage of alpha-(1 -> 6) linear linkages with very few alpha-(1 -> 3) branch points. The surface morphology and molecular weight distribution of purified dextran has also been included in this study.

Dextran is a bacterial exopolysaccharide (EPS) which has multifarious values in the area of medicine, food and fine chemical industries. It is a linear polymer of glucose joined mainly by alpha (1 -> 6) links and fewer alpha (1 -> 2), alpha (1 -> 3) and/or alpha (1 -> 4) links. Fermentation processes for EPS production are utterly expensive owing to purification costs, giving an advantage to the use of enzymes. Therefore, dextran polymer can be synthesized from sucrose by the action of dextransucrase enzyme which is an extracellular bacterial glucosyltransferase. In the current study, purified dextransucrase from Leuconostoc lactis KU665298 has been immobilized by using various entrapment methods and calcium-alginate was found to be the most suitable matrix for this enzyme immobilization with an immobilization efficiency of 90.7%. Different conditions were standardized for the entrapment of purified dextransucrase from L. lactis in calcium alginate matrix and enzyme was also characterized for various reaction parameters for its utility in dextran production in a laboratory fermenter. The dextran production by calcium-alginate immobilized dextransucrase was found to be 2.02 g/L on dry weight basis after 24 h of incubation.

Dextransucrase is a glucosyltransferase which synthesizes high molecular weight glucose polymer (dextran) from sucrose. Dextran has diverse applications in pharmaceutical, food and fine chemical industries. The combined effects of the agitation and aeration rates on the production of dextransucrase in laboratory fermenter were systematically investigated with Leuconostoc lactis KU665298 by applying RSM. Dextransucrase production from L. lactis was found to improve after the scale up of production process from shake flask (3.6 U/mL) to fermenter level (5.27 U/mL) at an agitation of 200 rpm and aeration of 0.85 vvm. The volumetric oxygen transfer coefficient (KLa) was used as the basis for the evaluation of aeration efficiencies. KLa value for most befitting fermentation condition aiding maximum dextransucrase production was 0.15 min-1. This is the first report in which RSM has been applied to design fermentation batches of different combinations of aeration and agitation rate in a laboratory fermenter to produce dextransucrase.

Dextransucrase is an important extracellular glucosyltransferase which catalyzes the synthesis of dextran from sucrose and valuable oligosachharides. Dextran is a high molecular weight glucose polymer, which has diverse applications in the area of medicine, food and fine chemical industries. A CCD based statistical approach was employed for the enhanced dextransucrase production by Leuconostoc lactis KU665298, isolated from sugarcane mill bagasse sample. The most determining factors (i.e. incubation time, inoculum size, sucrose and K2 HPO4 ) for dextransucrase production by L. lactis were screened by Plackett Burman design. Maximum dextransucrase activity of 3.6 U/mL was obtained with the experimental conditions of incubation time 18h with inoculum volume 6.5 (%, v/v) in a medium (pH 8), containing (%, w/v) sucrose 2, K2 HPO4 2.5, which corresponded well with the predicted value of 3.05 U/mL by the model.