The decarboxylation of pectin

Abstract

EARLY work on the occurrence of pectins and hemicelluloses showed that these substances were normally to be found in association in the cell-wall, the relative amount of each being dependent on the condition of the tissue, i.e. whether lignified or non-lignified [Clayson, Norris, and Schryver, 1921]. Subsequent work [Candlin and Schryver, 1928] indicated the existence of an intimate relation between the two classes of substances, since pectin was shown to undergo decarboxylation under the influence of alkali, yielding inter alia a substance of the hemicellulose type. The yield of hemicellulose obtained bythis treatment was invariably low, amounting only to 12-20 % of the pectin taken; further, these workers were unable to determine the nature of the products which represented the major part of the pectin. This might have been due to the fact that, as is well known, the sugars readily undergo profound changes in the presence of alkali, giving a variety of indefinite degradation products. It would follow therefore that if, as would seem possible from its accepted constitution, the pectin molecule yields sugars on decarboxylation, these latter would be destroyed immediately by the alkali present.Since, however, the decarboxylation of pectin is a reaction likely to throw some light upon the question of the relationship between certain of the cellwall substances, it is desirable to establish the nature of the substances other than hemicelluloses produced thereby. With this object it is necessary to employ a decarboxylating reagent which will not tend to destroy these other products, and it has been found possible to use hot water for this purpose. By this means, pectin has been shown to yield an insoluble substance, of the hemicellulose type, and one or more soluble substances, probably sugars.The insoluble product finally obtained appears to have undergone much more complete decarboxylation than the end-product (hemicellulose) described by Candlin and Schryver [1928]. From this insoluble product, a substance of the hemicellulose type has been separated, containing 6.2 % of uronic anhydride, and yielding a mixture of sugars on hydrolysis.The investigation of the soluble products is not complete, but it is thought that the observation that pectin can be decarboxylated by means of hot water is of sufficient interest to warrant the publication of a brief account of the work at the present stage.

Detection and identification of pathotypes of verocytotoxigenic Escherichia coli isolated from weaned piglets using gene probes for seven E. coli toxins

“…As these phenotypic assays on Vero cells are time-consuming and difficult to carry out on a large number of E. coli isolates the DNA colony hybridization genotypic assay using gene probes for EDP, SLTI and SLTII was performed with VTEC and non VTEC porcine isolates. The results of this work show that (i) EDP and SLTII probes cross-hybridized (ii) both EDP and SLTII probes hybridized to all VTEC but to none of the non VTEC isolates (iii) all E. coli isolates were negative using the gene probe for SLTI which does not seem to be common among porcine E. coli [6,7,20]. The genes encoding EDP show extensive homology with those encoding SLTII, but not with those encoding SLTI [12,13].…”

“…Some VTEC isolates associated with ED also produce one or more classical enterotoxins (Ent VTEC isolates) [4,[6][7][8]. The Ent VTEC isolates belonging to the O141 : K85 serotype usually produce STb alone ( [6], see also RESULTS).…”

“…Most of these verocytotoxigenic porcine E. coli (VTEC) are haemolytic and belong to the O138 : K81, O139 : K82, O141:K85 serotypes [4][5][6]. Some of these verocytotoxigenic E. coli (VTEC) can also produce one or more of the classical enterotoxins (Ent VTEC isolates) and for this reason are thought to be also involved in post-weaning diarrhea [4,[6][7][8].…”

Purification of Diphtheria Toxin and Diphtheria Toxoid

“…Holt ( 5 ) and Linggood (10) have found that diphtheria toxin can be converted into toxoid a t 300 C. without the loss of 15-30 per cent of the flocculating activity which usually occurs at 37-41O C . In preparatory work with this less harshly treated crude material, the latter was found to be decidedly better.…”