Topic
Levansucrase activity
About: Levansucrase activity is a research topic. Over the lifetime, 47 publications have been published within this topic receiving 1339 citations.
Papers
TL;DR: Identification of levan indicated that fructose was the building unit of leVan, and hence conversion of fructose to levan reached 84% using 1000 μg/ml enzyme protein.
Abstract: Bacillus subtilis NRC 33a was able to produce both inducible and constitutive extracellular levansucrase, respectively, using sucrose and glucose as carbon source. The optimal production of the levansucrase was at 30 degrees C. The effect of different nitrogen sources showed that baker's yeast with 2% concentration gave the highest levansucrase activity. Addition of 0.15 g/L MgSO(4) was the most favorable for levansucrase production. The enzymic synthesis of levan was studied using 60% acetone fraction. The results indicated that high enzyme concentrations produced increasing amounts of levan, and hence conversion of fructose to levan reached 84% using 1,000 microg/ml enzyme protein. Sucrose concentration was the most effective factor controlling the molecular weight of the synthesized levan. The conversion of fructose to levan was maximal at 30 degrees C. The time of reaction clearly affected the conversion of fructose to levan, which reached its maximum productivity at 18 hours (92%). Identification of levan indicated that fructose was the building unit of levan.
83 citations
TL;DR: The first-time isolation and molecular characterization of a L. mesenteroides levansucrase gene (m1ft) is reported, which shows an activity band at 103 kDa on a non-denaturing SDS-PAGE, indicating a dimeric form of the active M1FT.
72 citations
TL;DR: The elucidation of the role levansucrase in RFO metabolism by lactobacilli allowed the conversion or hydrolysis of RFOs in food fermentations.
70 citations
TL;DR: Cloned and characterized the enzymatic kinetics using levansucrase expressed in Escherichia coli and found that optimum pH for d-glucose production and levan formation was 6.0 and 8.0, respectively, whereas optimum temperature was 30°C and 4°C, respectively and the Km and Vmax values for levanucrase were calculated to be 47.81 and 57.47 μmole/min mg protein, respectively.
Abstract: Although levan produced by Bacillus amyloliquefaciens is known to have efficient immunostimulant property which gives 100% survival of common carp when infected with Aeromonas hydrophila, no detailed reports are available describing kinetic studies of D: -glucose production and levan formation. In this study, we cloned and characterized the enzymatic kinetics using levansucrase expressed in Escherichia coli. Optimum pH for D: -glucose production and levan formation was 6.0 and 8.0, respectively, whereas optimum temperature was 30 degrees C and 4 degrees C, respectively. The K (m) and V (max) values for levansucrase were calculated to be 47.81 mM sucrose and 57.47 1mole/min mg protein, respectively. Prominent expression of levansucrase was obtained through xylose induction in Bacillus megaterium, where most of the His(6)-tagged protein was secreted into the culture broth, giving levansucrase activity of 12,906 U/l. Response-surface methodology (RSM) was further employed to optimize the fermentation conditions and improve the level of levansucrase production. Maximum levansucrase activity of 20,251 U/l was obtained in 12 h of fermentation carried out at 28 degrees C, starting induction with 0.735% xylose when A (600) was 1.2, which was 1.6- and 62-fold higher than those obtained in the nonoptimized conditions for the recombinant strain and the native strain, respectively.
48 citations
TL;DR: It is demonstrated that virulence factor expression levels account for differences in disease severity caused by wild isolates of E. amylovora on apple trees.
Abstract: Lee, S. A., Ngugi, H. K., Halbrendt, N. O., O’Keefe, G., Lehman, B., Travis, J. W., Sinn, J. P., and McNellis, T. W. 2010. Virulence characteristics accounting for fire blight disease severity in apple trees and seedlings. Phytopathology 100:539-550. The gram-negative bacterium Erwinia amylovora is the causal agent of fire blight, the most destructive bacterial disease of rosaceous plants, including apple and pear. Here, we compared the virulence levels of six E. amylovora strains (Ea273, CFBP1367, Ea581a, E2002a, E4001a, and HKN06P1) on apple trees and seedlings. The strains produced a range of disease severity, with HKN06P1 producing the greatest disease severity in every assay. We then compared virulence characteristic expression among the six strains, including growth rates in immature apple fruit, amylovoran production, levansucrase activity, biofilm formation, carbohydrate utilization, hypersensitive cell death elicitation in tobacco leaves, and protein secretion profiles. Multiple regression analysis indicated that three of the virulence characteristics (amylovoran production, biofilm formation, and growth in immature apple fruit) accounted for >70% of the variation in disease severity on apple seedlings. Furthermore, in greenhouse-grown ‘Gala’ trees, >75% of the variation in disease severity was accounted for by five of the virulence characteristics: amylovoran production, biofilm formation, growth in immature apple fruit, hypersensitive cell death elicitation, and sorbitol utilization. This study demonstrates that virulence factor expression levels account for differences in disease severity caused by wild isolates of E. amylovora on apple trees. Additional keywords: disease incidence, DspA/E, HrpN, hypersensitive reaction, pCPP60, pEA29, type III secretion.
46 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 3 |
| 2020 | 2 |
| 2019 | 1 |
| 2017 | 5 |
| 2015 | 2 |
| 2013 | 1 |