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Dextranase is commonly used for eliminating dextran contamination in sugar factory. This research, dextranase from Aspergillus allahabadii X26, was produced, purified and characterized including on dextran hydrolysis. A. allahabadii X26 was cultured in a medium containing 1% dextran T2000 as a carbon source in 5-l fermenter aerobically at 30 °C and obtain 110 U/ml crude extracellular dextranase activity within 9 days of incubation. Extracellular dextranase could be purified by the 2 steps of ammonium sulfate precipitation and affinity chromatography using Sephacryl S-300 HR. This resulted in 6.5-fold and a 39.1% recovery yield obtaining 3009 U/mg mg protein. The purified enzyme exhibited 66 kDa on SDS-PAGE and was specified as a glycoprotein. The optimum pH and temperature for enzyme activity were 5.8 and 55 °C, respectively. The enzyme exhibited thermostability in the range of 20–50 °C and pH 5–9 over the incubation period of 1.5 h. The dextranase activity was enhanced by Co2+, Mn2+ and Ca2+, whereas most ions and reagents did not inhibit its activity. The enzyme only had specificity to the α(1 → 6) glycosidic bond of dextran. Partial sequences of the enzyme determined by an ESI mass spectrometer showed similarity toward dextranase GH49. This purified dextranase (0.2 U/ml) from A. allahabadii X26 could degrade high molecular weight dextran into fragments of 5–10 kDa and oligodextrans within 5 min. These A. allahabadii X26 dextranase properties indicated high potential for dextran elimination in sugar production process.

Dextran from Weissella confusa R003 isolated from sugar cane juice was purified and characterized. Dextran synthesis was performed by fermenting W. confusa R003 in MRS medium containing 10% (w/v) sucrose with continuous shaking at 125 rpm and at 30°C. For 24 hours, the 50% efficiency yield was obtained. Dextran in the culture medium was purified by ethanol precipitation. Structural analysis of dextran using 1H NMR, 13C NMR, and 2D NMR techniques showed the existence of glucoses with 97.4% α (1→6) linkage in the main chains and 2.6% α (1→3) in branches. The estimation of molecular weight by dynamic light scattering exhibited average molecular weight of 1.0 × 104 kDa. At low concentration (2.5% w/v), dextran behaved like liquid structure, while, increasing the concentration (5.0 and 10.0% w/v), it was revealed as viscoelastic behavior. The highest gelling phenomenon was found in the concentration of 10% w/v and at 37°C. Due to its production and properties, it may be suitable for commercial production and application in the field of foods as well as hydrogel.

Dextran is a polysaccharide consisting of glucose monomers linked mainly by α(1–6) bonds, produced by numerous microorganisms. It is well known that dextran in cane detrimentally affects processing in the sugar industry. Many microorganisms have been isolated from sugarcane juice during the milling process at Mitr Phuveing Sugar Factory. These organisms were screened for their dextran producing property by selecting mucoid colonies on plate count agar (PCA), MRS agar and malt extract (ME) agar medium containing 10% sucrose. The secondary and tertiary screening was accomplished by growing them in sugarcane juice and complete liquid medium (CM) adding 10% sucrose, aerobically at the appropriate temperature for each isolate. The rapidly growing strains were selected. The bacterial strains were Klebsiella pneumoniae, Enterobacter cloacae, and Lactobacillus fermentum. Among these K. pneumoniae P100 produced the maximum concentration of dextran (6,800 ppm) at stationary phase within 12 h of incubation in CM. Biocide, Dimethyl Benzyl Ammonium Chloride (DBAC) (2 ppm) commonly used to inhibit some microorganisms in the modern cane milling process at Mitr Phuveing Sugar Factory, could not inhibit K. pneumoniae P100 within 30 minutes. From these experiments, the factory has changed the sanitization during the milling process, which has saved on biocide costs.