Potential of dry fractionation of wheat bran for the development of food ingredients,part II: Electrostatic separation of particles

Wheat bran is a composite material made of several layers, such as pericarp, testa and aleurone. It could be fractionated into purified fractions, which might either be used as food ingredients, or serve as a starting material for extraction of bioactive compounds. The aim of this work was to evaluate the potential of using electrostatic separation as a way to obtain purified fractions from wheat bran. Ultrafine-ground bran obtained either by cryogenic grinding or by grinding at ambient temperature was used as starting material. The ultrafine bran was then charged by tribo-electrification and introduced in a chamber containing two high voltage electrodes, where bran particles were separated depending on their acquired charge, allowing positively and negatively charged fractions to be collected separately. The particle size distribution, microstructure and biochemical composition of the obtained fractions were studied. The charge of the particles was influenced by their biochemical composition: particles rich in highly branched and cross-linked arabinoxylans (pericarp) were separated from particles rich in β-glucan, ferulic acid and para-coumaric acid (aleurone cell walls). The testa and the intracellular compounds from aleurone were not highly charged, neither positively nor negatively. The most positively charged fraction represented 34% of the initial bran, and contained 62% of the ferulic acid present in the initial bran. The yield of the separation process was good (5.4% loss), and could be further increased.     

Fine root biomass in relation to site and stand characteristics in Norway spruce and Scots pine stands

Variations in fine root biomass of trees and understory in 16 stands throughout Finland were examined and relationships to site and stand characteristics determined. Norway spruce fine root biomass varied between 184 and 370 g m(-2), and that of Scots pine ranged between 149 and 386 g m(-2). In northern Finland, understory roots and rhizomes (< 2 mm diameter) accounted for up to 50% of the stand total fine root biomass. Therefore, the fine root biomass of trees plus understory was larger in northern Finland in stands of both tree species, resulting in a negative relationship between fine root biomass and the temperature sum and a positive relationship between fine root biomass and the carbon:nitrogen ratio of the soil organic layer. The foliage:fine root ratio varied between 2.1 and 6.4 for Norway spruce and between 0.8 and 2.2 for Scots pine. The ratio decreased for both Norway spruce and Scots pine from south to north, as well as from fertile to more infertile site types. The foliage:fine root ratio of Norway spruce was related to basal area and stem surface area. The strong positive correlations of these three parameters with fine root nitrogen concentration implies that more fine roots are needed to maintain a certain amount of foliage when nutrient availability is low. No significant relationships were found between stand parameters and fine root biomass at the stand level, but the relationships considerably improved when both fine root biomass and stand parameters were calculated for the mean tree in the stand. When the northern and southern sites were analyzed separately, fine root biomass per tree of both species was significantly correlated with basal area and stem surface area per tree. Basal area, stem surface area and stand density can be estimated accurately and easily. Thus, our results may have value in predicting fine root biomass at the tree and stand level in boreal Norway spruce and Scots pine forests.     

Detection of nitrogen transfer from N<Subscript>2</Subscript>-fixing shade trees to cacao saplings in <Superscript>15</Superscript>N labelled soil: ecological and experimental considerations

Theobroma cacao seedlings were grown alone (TCA) or associated with saplings of N₂-fixing shade trees Gliricidia sepium and Inga edulis in 200 l of ¹⁵N labelled soil within a physical root barrier for studying direct nitrogen transfer between the trees and cacao. Root:shoot partitioning ratio for sapling total N was lower than biomass root:shoot ratio in all species. Sapling total ¹⁵N was partitioned between root and shoot in about the same ratio as total N in cacao and inga but in gliricidia much higher proportion of ¹⁵N than total N was found in roots. Thus, whole plant harvesting should be used in ¹⁵N studies whenever possible. Average percentage of fixed N out of total tree N was 74 and 81% for inga estimated by a yield-independent and yield-dependent method, respectively, and 85% for gliricidia independently of estimation method. Strong isotopic evidence on direct N transfer from trees to cacao was observed in two cases out of ten with both tree species. Direct N transfer was not correlated with mycorrhizal colonisation of either donor or receiver plant roots. Direct N transfer from inga and gliricidia to cacao is conceivable but its prevalence and the transfer pathway via mycorrhizal connections or via reabsorption of N-rich legume root exudates by cacao require further study. Competition in the restricted soil space may also have limited the apparent transfer in this study because the trees accumulated more soil-derived N than cacao in spite of active N₂ fixation.     

Leiomodin is an actin filament nucleator in muscle cells

Initiation of actin polymerization in cells requires nucleation factors. Here we describe an actin-binding protein, leiomodin, that acted as a strong filament nucleator in muscle cells. Leiomodin shared two actin-binding sites with the filament pointed end-capping protein tropomodulin: a flexible N-terminal region and a leucine-rich repeat domain. Leiomodin also contained a C-terminal extension of 150 residues. The smallest fragment with strong nucleation activity included the leucine-rich repeat and C-terminal extension. The N-terminal region enhanced the nucleation activity threefold and recruited tropomyosin, which weakly stimulated nucleation and mediated localization of leiomodin to the middle of muscle sarcomeres. Knocking down leiomodin severely compromised sarcomere assembly in cultured muscle cells, which suggests a role for leiomodin in the nucleation of tropomyosin-decorated filaments in muscles.     

Effects of nitrogen source and defoliation on growth and biological dinitrogen fixation of Gliricidia sepium seedlings

Effects of four N sources and two defoliation treatments on growth and nitrogenase activity of Gliricidia sepium (Jacq.) Walp seedlings were studied in a greenhouse. All nutrients were supplied in irrigation water to the sterile growing medium. The N sources were: (1) 100 mg l(-1) of N supplied as NO(3) (-) (high-NO(3) (-)), (2) 50 mg l(-1) of N supplied as NO(3) (-) and inoculation with Rhizobium spp. medium-NO(3) (-)), (3)100 mg l(-1) of N supplied as NH(4)NO(3), and (4) inoculation with Rhizobium spp without mineral N (N(2)). At 35 weeks after sowing, mean total biomass was 130.5, 50.5, 22.9 and 17.4 g seedling(-1) in the NH(4)NO(3), N(2), medium-NO(3) (-) and high-NO(3) (-) treatments, respectively. The root/shoot ratio was high in all of the N treatments (1.73-2.77) because the seedlings had big taproots. The medium-NO(3) (-) treatment completely inhibited nodulation, whereas seedlings in the N(2) treatment were profusely nodulated. At 32 weeks after sowing, groups of seedlings in the N(2) and high-NO(3) (-) treatments were subjected to 50 or 100% defoliation. Closed-chamber acetylene reduction assays of intact root systems were conducted to compare nitrogenase activity at 7, 14 and 28 days after defoliation (DAD). At 7 and 14 DAD, nitrogenase activity of completely and partially defoliated seedlings was about 10 and 60%, respectively, of that of undefoliated controls. At 28 DAD, nitrogenase activity of completely defoliated seedlings was twice the predefoliation value, whereas nitrogenase activity of partially defoliated seedlings was only 87% of the predefoliation value. Recovery of nitrogenase activity was strongly correlated with foliage regrowth in the completely defoliated seedlings, but not in the partially defoliated seedlings. Abundant belowground C and N reserves in the large taproot probably contributed to the rapid recovery from defoliation. Accumulation of belowground biomass may also improve defoliation tolerance of mature trees.     

Triacylglycerols, glycerophospholipids, tocopherols, and tocotrienols in berries and seeds of two subspecies (ssp. sinensis and mongolica) of Sea Buckthorn (Hippophaë rhamnoides)

Berries and seeds of two subspecies (ssp. sinensis and mongolica) of sea buckthorn (Hippopha? rhamnoides L.) were compared in terms of triacylglycerols, glycerophospholipids, tocopherols, and tocotrienols. The berries of ssp. mongolica contained less oleic acid (4.6 vs 20.2%, p < 0.001) and more palmitic (33.9 vs 27.4%, p < 0.01) and palmitoleic (32.8 vs 21.9%, p < 0.05) acids in triacylglycerols than those of ssp. sinensis. The proportions of linoleic acid (32.1 vs 22.2%, p < 0.01, in berries; 47.7 vs 42.7%, p < 0.05, in seeds) and palmitic acid (21.1 vs 16.4%, p < 0.001, in berries; 17.0 vs 14.1%, p < 0.05, in seeds) in glycerolphospholipids were higher in ssp. mongolica than in ssp. sinensis, and vice versa with oleic acid (4.3 vs 18.5% in berries, 10.0 vs 22.2% in seeds, p < 0.001). A higher proportion of alpha-linolenic acid was also found in the glycerophospholipids of ssp. sinensis berries (16.2 vs 10.1%, p < 0.001). alpha-, beta-, gamma-, and delta-tocopherols constituted 93-98% of total tocopherols and tocotrienols in seeds, and alpha-tocopherol alone constituted 76-89% in berries. The total contents of tocopherols and tocotrienols varied within the ranges of 84-318 and 56-140 mg kg(-1) in seeds and whole berries, respectively. The seeds of ssp. mongolica were a better source of tocopherols and tocotrienols than those of ssp. sinensis (287 vs 122 mg kg(-1), p < 0.001). The compositional differences between the two subspecies should be considered when the berries are bred and exploited for nutritional purposes.     

Effects of thinning and fertilization on wood properties and economic returns for Norway spruce

The effects of silviculture on wood and tracheid properties, and economic returns of Norway spruce (Picea abies (L.) Karst.) were investigated in two case studies, one comparing different thinning intensity in southeastern Finland and the other considering the effects of optimal nutrient addition in northern Sweden. Models for predicting the wood and tracheid properties of Norway spruce were integrated into a distance-independent process-based growth and yield model. Increasing the thinning intensity resulted in a lower mean wood density, tracheid length, and latewood proportion in harvested wood. Wood density and tracheid length of harvested pulpwood slightly decreased in later thinnings and final cuts. Thinning regimes with high early growing stock and decreasing later growing stock were most profitable. Nutrient addition accelerated volume growth and increased the value growth. The increase in volume growth due to nutrient addition more than offset the economic influence of the loss in wood density and tracheid length.