Rheological properties of mixtures of κ-carrageenan from Hypnea musciformis and galactomannan from Cassia javanica

Mixed gels of κ-carrageenan (κ-car) from Hypnea musciformis and galactomannans (Gal) from Cassia javanica (CJ) and locust bean gum (LBG) were compared using dynamic viscoelastic measurements and compression tests. Mixed gels at 5 g/l of total polymer concentration in 0.1 M KCl showed a synergistic maximum in viscoelastic measurements for κ-car/CJ and κ-car/LBG at 2:1 and 4:1 ratios, respectively. The synergistic maximum obtained from compression tests carried out for mixed gels at 10 g/l of total polymer concentration in 0.25 M KCl was the same for both κ-car/CJ and κ-car/LBG gels. An enhancement in the storage modulus (G′) and the loss modulus (G″) was observed in the mechanical spectra for the mixtures in relation to κ-car. The proportionally higher increase in G″ compared with G′, as indicated by the values of the loss tangent (tan δ), suggests that the Gal adhere non-specifically to the κ-car network.     

高效液相色谱法分析猪屎豆种子胶多糖中的单糖组成

建立了一种采用SUGAR SP-G 0810(Pb型)糖分析色谱柱,以纯水为流动相,利用示差折光检测器的高效液相色谱外标法直接分离分析半乳甘露聚糖胶中单糖组成的方法。木糖、葡萄糖、半乳糖和甘露糖的分离在20 min内完成,检出限分别达到2.0μg,20μg,1.0μg和20μg,线性范围为2～10 mg/mL。该方法简便、快速、重现性好,用于猪屎豆种子胶多糖中单糖组分的测定,并进行回收率试验,结果5次测定的半乳糖和甘露糖的回收率分别为95.83%和103.68%,RSD分别为1.53%和1.50%。     

Rheological properties of mixtures of kappa-carrageenan from Hypnea musciformis and galactomannan from Cassia javanica

Mixed gels of κ-carrageenan (κ-car) from Hypnea musciformis and galactomannans (Gal) from Cassia javanica (CJ) and locust bean gum (LBG) were compared using dynamic viscoelastic measurements and compression tests. Mixed gels at 5 g/l of total polymer concentration in 0.1 M KCl showed a synergistic maximum in viscoelastic measurements for κ-car/CJ and κ-car/LBG at 2:1 and 4:1 ratios, respectively. The synergistic maximum obtained from compression tests carried out for mixed gels at 10 g/l of total polymer concentration in 0.25 M KCl was the same for both κ-car/CJ and κ-car/LBG gels. An enhancement in the storage modulus (G′) and the loss modulus (G″) was observed in the mechanical spectra for the mixtures in relation to κ-car. The proportionally higher increase in G″ compared with G′, as indicated by the values of the loss tangent (tan δ), suggests that the Gal adhere non-specifically to the κ-car network.     

The role of carbohydrates in seed germination and seedling establishment of Himatanthus sucuuba, an Amazonian tree with populations adapted to flooded and non-flooded conditions

Background and Aims

In the Amazonian floodplains plants withstand annual periods of flooding which can last 7 months. Under these conditions seedlings remain submerged in the dark for long periods since light penetration in the water is limited. Himatanthus sucuuba is a tree species found in the ‘várzea’ (VZ) floodplains and adjacent non-flooded ‘terra-firme’ (TF) forests. Biochemical traits which enhance flood tolerance and colonization success of H. sucuuba in periodically flooded environments were investigated.

Methods

Storage carbohydrates of seeds of VZ and TF populations were extracted and analysed by HPAEC/PAD. Starch was analysed by enzyme (glucoamylase) degradation followed by quantification of glucose oxidase. Carbohydrate composition of roots of VZ and TF seedlings was studied after experimental exposure to a 15-d period of submersion in light versus darkness.

Key Results

The endosperm contains a large proportion of the seed reserves, raffinose being the main non-structural carbohydrate. Around 93 % of the cell wall storage polysaccharides (percentage dry weight basis) in the endosperm of VZ seeds was composed of mannose, while soluble sugars accounted for 2·5%. In contrast, 74 % of the endosperm in TF seeds was composed of galactomannans, while 22 % of the endosperm was soluble sugars. This suggested a larger carbohydrate allocation to germination in TF populations whereas VZ populations allocate comparatively more to carbohydrates mobilized during seedling development. The concentration of root non-structural carbohydrates in non-flooded seedlings strongly decreased after a 15-d period of darkness, whereas flooded seedlings were less affected. These effects were more pronounced in TF seedlings, which showed significantly lower root non-structural carbohydrate concentrations.

Conclusions

There seem to be metabolic adjustments in VZ but not TF seedlings that lead to adaptation to the combined stresses of darkness and flooding. This seems to be important for the survival of the species in these contrasting environments, leading these populations to different directions during evolution.     

Expression of Rice (Oryza sativa L. var. Nipponbare) α-Galactosidase Genes in Escherichia coli and Characterization

Two putative α-galactosidase genes from rice (Oryza sativa L. var. Nipponbare) belonging to glycoside hydrolase family 27 were cloned and expressed in Escherichia coli. These enzymes showed α-galactosidase activity and were purified by Ni Sepharose column chromatography. Two purified recombinant α-galactosidases (α-galactosidase II and III; α-Gal II and III) showed a single protein band on SDS–PAGE with molecular mass of 42 kDa. These two enzymes cleaved not only α-D-galactosyl residues from the non-reducing end of substrates such as melibiose, raffinose, and stachyose, but also liberated the galactosyl residues attached to the O-6 position of the mannosyl residue at the reducing-ends of mannobiose and mannotriose. In addition, these enzymes clipped the galactosyl residues attached to the inner-mannosyl residues of mannopentaose. Thus, α-Gal II catalyzes efficient degalactosylation of galactomannans, such as guar gum and locust bean gum.     

Incorporation of galactomannans in the diet of newly weaned piglets: Effect on bacteriological and some morphological characteristics of the small intestine

In search of substances replacing antibiotics as growth promoters for farm animals, non-digestible oligosaccharides (NDO) or non-starch polysaccharides (NSP) have been proposed as possible alternatives. In this context, the influence of galactomannans on bacteriological and morphological aspects of the gastrointestinal tract in weanling pigs was investigated. Four groups of five newly weaned piglets received one of the following diets: control feed (C), C supplemented with guar gum (1%), C supplemented with locust bean gum (1%) and C supplemented with 10% of carob tree seeds meal as source of locust bean gum. The animals were euthanized after 11?–?12 days and digesta were sampled in stomach, jejunum (proximal and distal) and caecum, while mucosal scrapings and ring shaped tissue samples were taken of proximal and distal jejunum. On these samples bacteriological, biochemical and morphological determinations were carried out. Total count of bacteria in digesta and mucosal scrapings was not influenced by the different diets, with the exception of the proximal jejunum where a small decrease (0.5 log₁₀ CFU) was noted with the guar gum and carob tree seeds diet. The number of E. coli increased by feeding both gums and carob tree seeds. With the latter diet, higher counts of streptococci were observed. In agreement with the lower concentration of lactic acid in jejunal contents, guar gum decreased the number of lactobacilli. Locust bean gum decreased the molar proportion of acetate in caecal contents while butyrate and valerate were augmented. Feeding the carob tree seeds resulted in shorter villi and a lower villus height/crypt depth ratio in the jejunum mucosa, which was an indication for a faster renewal rate of the epithelium. Both locust bean gum feeds significantly lowered the mitotic index in the crypts of the small intestine. Only with the carob tree seeds diet, viscosity of jejunal contents was increased. In conclusion, the effects of the addition of 1% of pure guar gum or locust bean gum were inconsistent and not very outspoken, whereas 10% of carob tree seeds meal in the diet resulted in influences on intestinal characteristics at the bacteriological and morphological level.