Higher Total Carbohydrate Content Research Articles

Enhanced accumulation of starch and total carbohydrates in alginate-immobilized Chlorella spp. induced by Azospirillum brasilense: I. Autotrophic conditions

The effect of the microalgae-growth promoting bacterium Azospirillum brasilense on accumulation of total carbohydrates and starch in two species of Chlorella (Chlorella vulgaris and Chlorella sorokiniana), when the bacterium and each microalga were jointly immobilized in alginate beads was studied under autotrophic conditions for 144h in synthetic medium. The interaction of the bacterium with the microalgae enhanced accumulation of total carbohydrate and starch. Cells of Chlorella accumulated the highest amounts of carbohydrate after incubation for 24h. Yet, this did not coincide with the highest affinity and volumetric productivity measured in these cultures. However, after incubation for 72h, mainly in jointly immobilized treatments of both microalgae species, the cultures reached their highest total carbohydrate content (mainly as starch) and also the highest affinity and volumetric productivity. These results demonstrate the potential of A. brasilense to affect carbohydrates and starch accumulation in Chlorella spp. when both microorganisms are co-cultured, which can be an important tool for applications of microalgae.

Cell wall metabolism in gibberellin-treated persimmon fruits

The application of gibberellin [GA3] to persimmon fruits as an orchard spray, at least 2 weeks prior to harvest, has been shown to delay ripening of the fruit on the tree and its rate of softening after harvest. This effect persisted during and after cold storage. The delay in softening has been attributed to the effect of the phytohormone on cell wall metabolism. To examine this hypothesis, cell walls of GA3-treated fruit were compared to those of non-treated fruit. Comparison between fruit was from harvest till the termination of post-storage softening. The study included TEM examinations, assay of certain hydrolase activities and determination of compositional changes occurring in the various cell-wall carbohydrate polymers. Our findings indicate that GA3 either delays or inhibits all of the cell wall changes that were found to accompany fruit softening, including dissolution of the middle lamella, separation of the plasmalemma from the cell-wall, mitigation of the structural coherence and density of the primary cell wall, increases solubilization of pectic polymers, loss of neutral sugars, predominantly arabinose and galactose, and increased activities of exo-polygalacturonase [PG] and endo-1,4-β-glucanase [EGase]. The principal discernible compositional difference between GA3-treated fruit and control fruit at harvest was a higher total carbohydrate content in the cell wall material extracted from GA3-treated fruit, which was due chiefly to an increased amount of cellulose.

Characterization of Vitamin B12-Binding Proteins Isolated from Human Milk and Saliva by Affinity Chromatography

Abstract Human tissues and body fluids contain a number of immunologically related R type vitamin B12-binding proteins that can often be distinguished from one another by the use of ion exchange chromatography, electrophoresis, and gel filtration. The single major vitamin B12-binding proteins present in human milk and saliva are included in this group of proteins and have been isolated in homogeneous form with the use of affinity chromatography on vitamin B12-Sepharose. Both proteins bind approximately 20.5 µg of vitamin B12 per mg of protein and are indistinguishable in terms of absorption spectra, immunodiffusion with rabbit antihuman milk and anti-human saliva vitamin B12-binding protein sera, molecular weight (61,000 to 63,000) as determined by sedimentation equilibrium ultracentrifugation, total amino acid composition, migration on disc gel electrophoresis, and sequence of the first 13 NH2-terminal amino acids (Glu-Ile-Ser-Glu-Val-Ser-Glu-Glu-Asn-Tyr-Ile-Arg-Leu). Both proteins contain fucose, galactose, mannose, galactosamine, glucosamine, and sialic acid residues, although the saliva vitamin B12-binding protein contains more fucose and galactose and has a higher total carbohydrate content (39.9%) than the milk protein (34.5%). Elevated values for molecular weight were obtained for both proteins with the use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, although the respective values obtained for the saliva protein (95,000 and 148,000) were significantly greater than those obtained for the milk protein (90,000 and 136,000). These studies suggest that differences among the various human R type vitamin B12-binding proteins may be due to differences in carbohydrate content rather than to differences in amino acid composition or sequence.