Sugar beet pectin

Prior to WWII, attempts were made in Germany to nitrate pectins prepd by extracting sugar beet shavings (Refs 1,3 4). However, the... 

In some species, onion (2), tomato, and sugar beet (13), the interface regions between cells, ie the middle lamella and the cell corners, are rich in relatively unesterified pectins which may function in cell-cell adhesion and play an important structural role in tissue integrity. Cell corners, in particular, may act as joists in the scaffolding function of the wall, bearing much of the mechanical load of the tissue (Jeronomidis, pers. comm.). In Zinnia leaves, although all of the cell-walls contain methyl-esterified pectin. 

Rombouts, F.M. and Thibault, J.F. (1986) Sugar beet pectins chemical structure and gelation through oxidative coupUng. In Chemistry and Function of Pectins, edited by M.L. Fishman, et al, pp. 49-60. American Chemical Society, Washington, DC. 

The same enzyme (RGAE) could be purified from A. niger, together with two other esterases a feruloyl esterase (FAE) and an acetyl esterase (PAE) specific for the removal of one type of acetyl group present in the smooth regions of sugar-beet pectin. 

The discovery of these enzymes enables a better structural characterisation of the hairy (ramified) regions of pectin, as already demonstrated by Schols et al. (1990b) and also of native plant cell wall pectin (Schols et al., 1995). In this study we show how the two exo-enzymes of the above described series, the RG-rhamnohydrolase and the RG-galacturonohydrolase, can be used as tools in the characterisation of unknown RG fragments. These unknown fragments were the products of RG-hydrolase or RG-lyase action toward linear RG oligomers (RGO s), which were produced by acid hydrolysis of sugar beet pulp. 

Extrusion-cooking of cell-wall rich products (e.g. wheat bran, apple pomace, citrus peels, sugar-beet pulp, pea hulls.) led to an important solubilisation of polysaccharides of various types without extensive degradation of the polymeric structure. The possibility of obtaining gelled systems directly with the extruded pectin-rich materials was demonstrated. 

Extrusion-cooking increased very significantly the water-solubility of plant cell wall rich-materials. High amounts of pectins can be solubilised from sugar-beet pulp, citrus peels or apple pomace. 

To improve production of rhamnogalacturonase by Aspergillus aculeatus CBS 115.80 shake flask ejqjeriments were performed on several substrates. Cross reactivity was found after transfer to thamnose in combination with galacturonic acid and on apple pectin, citrus pectin, beet pectin and sugar beet pulp. No cross reactivity was found after transfer to meda containing simple carbon sources such as sucrose, glucose, fiuctose, rhamnose or galacturonic acid. 

Figure 2. Influence of the ionic strength and the polymer concentration on the binding isotherms of Pb2+ by sugar-beet pectins in water (empty symbols) and in 0.1 M NaNOs (full symbols) at 25°C ( ) 2 mequiv. COO. l-, ( ) 8 mequiv. COO-.l-i (—) total binding of added Pbz+.

Figure 3. Influence the metal ion type on the binding isotherms of sugar-beet (A) and citrus (B) pectins at 2 mequiv. COO-.l- in 0.1 M NaNOs and at 25 °C. Symbols as in figure 1.

In water, Scatchard plots showed clear concave-shaped curves whatever the pectin origin (figure 4A). Nevertheless, differences between sugar-beet and citrus pectins appeared in presence of ionic strength. While citrus pectins exhibited convex-shaped curves whatever the metal ion, sugar-beet pectins display convexe curvature for Cu2+ and Pb2+ but concave-shaped curves for the other three cations (figure 4B, in the case of Ni2+). 

Binding isotherms presented the same characterisitics for sugar-beet and citrus pectins according to the pectin concentration and the conditions of ionic strength. The single case of... 

Interactions studies between some divalents metal ions and pectins from citms and sugar-beet revealed that the chemical structure of the latter, namely the presence of acetyl functions, induces differences of binding process whereas the scale of selectivity was not affected. Some further studies could be carried out on the correlation between the binding mode and the degree of acetylation. Lastly, pectins showed a clear scale of selectivity towards heavy metals with high capacities of binding which make them suitable to be used in waste-waters depollution. 

To date, the structural features of pectic polysaccharides and plant cell walls have been studied extensively using chemical analysis and enzymatic degradation. In addition, research on isolation and physicochemical characterisation of pectin from citrus peels, apple peels, sunflower head residues and sugar beet pulp has been reported (2). However, the pectic polysaccharides extracted from wheat straw have only previously been reported by Przeszlakowska (3). The author extracted 0.44% pectic substances from Author to whom correspondence should be addressed. 

Acetyl esterase (AE) has been purified to homogeneity from orange peels. The purification steps included cation exchange chromatography and gel filtration. The enzyme has affinity for triacetin and sugar beet pectin with K, of 39 mM and of 26 mg/ml, respectively. AE has a MW of 42 kD and is a monomer. The isoelectric point is at pH > 9. 

AE catalyses the cleavage of acetyl groups from different substrates. The enzyme activity was determined by measuring the release of acetic acid. The amount of acetic acid was measured spectrophotometrically using an acetic acid analysis kit (Boehringer, Mannheim). The activity of AE was measured in 0.6% sugar beet pectin solubilised in 25 mM Na-succinate pH 6.2 and incubated with enzyme fraction in total 500 nl assay. The samples were incubated at 40°C and aliquots were examined after 0, 1, 2 and 3 hours of incubation. The enzyme reaction was stopped by incubating the samples at lOO C for 5 min. Precipitated... 

The AE activity was strongly dependent of the pH. When measured with 1 % sugar beet pectin and 80 mM triacetin an optimum was found at pH 5 - 5.5. 

The affinity for sugar beet pectin was determined using a Lineweaver-Burk plot. The K was calculated to be 26 mg/ml for sugar beet pectin whereas the Kj, for triacetin was 39 mM. This showed a very low affinity for sugar beet pectin and triacetin. Substrate specifity of purified AE is summarized in table 2. 

Enzymes can be used to specifically modify the pectins. Pectin methyl esterase is already widely used to adjust the gelling properties of commercially available pectins. The acetyl esters also strongly affect the gelation [2,3] and removal is important for the upgrading of sugar beet pectin, extractable from a by-product of the sugar industry. 

KP pectin from sugar beet pulp was from Kobenhavns Pectinfabrik (Lille Skensved, Denmark). G-pectin was extracted from the whole sugar beet by Grindsted Products, Denmark. A preparation of modified hairy regions (MHR) was isolated from apple [5]. The non pectic acetylated substrates are described elsewhere [6,7,8]. 

This novel enzyme was the only esterase able to release acetyl from sugar beet pectin and removed about 30% of the total acetyl groups present. It also caused the release of acetyl groups from a range of other acetylated substrates, either synthetic or extracted from plants, in small amounts. PAE had an apparent molecular weight of 60 kDa and showed optimal activity at pH 5.5 and a temperature of 50 C. The enzyme is sensitive to buffer composition and requires a bivalent cation for optimal activity and stability. In purified form this enzyme proved unstable, especially in phosphate buffers. 

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