Some important process properties of α-l,4-D-ghican phosphorylases isolated from the bacteriumCorynebacterium callunae and potato tubers (Solatium tuberosum) were compared. Apart from minor differences in their stability and specificity (represented by the maximum degree of maltodextrin
conversion) and a 10-fold higher affinity of the plant phosphorylase for maltodextrin (KM of 1.3 g/L at 300 mM of orthophosphate), the performances of both enzymes in a continuous ultrafiltration membrane reactor
were almost identical. Product synthesis was carried out over a time course of 300–400 h in the presence or absence of auxiliary
pullulanase (increasing the accessibility of the glucan substrate for phosphorolytic attack up to 15–20%). The effect of varied
dilution rate and reaction temperature on the resulting productivities was quantitated, and a maximum operational temperature
of 40°C was identified. 相似文献
The wood-degrading fungus Trametes multicolor secretes several laccase isoforms when grown on a simple medium containing copper in the millimolar range for stimulating
laccase synthesis. The main isoenzyme laccase II was purified to apparent homogeneity from the culture supernatant by using
anion-exchange chromatography and gel filtration. Laccase II is a monomeric glycoprotein with a molecular mass of 63 kDa as
determined by sodium dodecylsulfate polyacrylamide gel electrophoresis, contains 18% glycosylation, and has a pI of 3.0. It oxidizes a variety of phenolic substrates as well as ferrocyanide and iodide. The pH optimum depends on the substrate
employed and shows a bell-shaped pH activity profile with an optimum of 4.0 to 5.0 for the phenolic substrates, while the
nonphenolic substrates ferrocyanide and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonate) show a monotonic pH profile with
a rate decreasing with increasing pH. 相似文献
A number of wild-type isolates ofSclerotium rolfsii were screened for their capacity to produce lignocellulolytic enzymes when grown on a cellulose-based medium.S. rolfsii proved to be an efficient producer of hemicellulolytic enzymes under the conditions selected for this screening, although there was a great variability in enzyme activities formed by the different isolates. In addition to xylanase and mannanase, which were produced in remarkably high levels, a number of accessory enzymes, which are important for the complete degradation of substituted hemicelluloses and include a-arabinosidase, acetyl esterase, and a-galactosidase, are formed byS. rolfsii. Efficient production of xylanase and mannanase was achieved when cellulose-based media were used for growth. Under these conditions, enhanced levels of endoglucanase were formed as well. Formation of xylanase and mannanase could be more specifically induced when using xylan or mannan as growth substrates, although the enzyme activities thus obtained were significantly lower compared to cultivations on cellulose as main inducing substrate.
Abstract In synthetic pathways to complex carbohydrates such as oligosaccharides or nucleotide sugars the activated sugar 1-phosphates serve as important starting molecules. In this study the enzymatic synthesis of α-glucose-1-phosphate (Glc-1-P) has been investigated using a new bacterial α-glucan phosphorylase from Corynebacterium callunae. The major factors governing the rate of reaction and the attainable degree of substrate conversion have been identified and, accordingly, for optimizing the yield and limiting reaction time for the enzymatic process several points must be considered: (i) the pH-dependent equilibrium of reaction, (ii) product inhibition of the phosphorylase and (iii) enzymatic cleavage of α-1,6 glycosidic linkages present in α-1,4-glucans such as starch or maltodextrins by pullulanases to improve their phosphorolytic conversion. Results obtained in continuous experiments with the phosphorylase retained in an ultrafiltration membrane reactor confirmed the complete operational stability of the enzyme for several days at 30 °C. Since no more than approximately 18 % of the inorganic phosphate can be converted into Glc-1-P an efficient procedure for phosphate and product recovery will be particularly important. 相似文献
Applied Biochemistry and Biotechnology - Recombinant β-glycosidase CelB from the hyperthermophilic archaeon Pyrococcus furiosus was produced through expression of the plasmid-encoded gene in... 相似文献
During a screening for the enzyme pyranose 2-oxidase (P2O) which has a great potential as a biocatalyst for carbohydrate transformations,
Trametes multicolor was identified as a promising, not-yet-described producer of this particular enzyme activity. Furthermore,
it was found in this screening that the enzyme frequently occurs in basidiomycetes. Intracellular P2O was produced in a growth-associated
manner by T. multicolor during growth on various substrates, including mono-, oligo-, and polysaccharides. Highest levels
of this enzyme activity were formed when lactose or whey were used as substrates. Peptones from casein and other casein hydrolysates
were found to be the most favorable nitrogen sources for the formation of P2O. By applying an appropriate feeding strategy
for the substrate lactose, which ensured an elevated concentration of the carbon source during the entire cultivation, levels
of P2O activity obtained in laboratory fermentations, as well as the productivity of these bioprocess experiments, could be
enhanced more than 2.5-fold. 相似文献
Applied Biochemistry and Biotechnology - The production of sorbitol and gluconic acid by isolated glucose-fructose oxidoreductase (GFOR) fromZymomonas mobilis has been studied in a convective,... 相似文献
Applied Biochemistry and Biotechnology - The white-rot fungus Trametes multicolor MB 49 has been identified as an excellent producer of the industrially important enzyme laccase. The formation of... 相似文献