Variability in Arabinoxylan,Xylanase Activity,and Xylanase Inhibitor Levels in Hard Spring Wheat

Arabinoxylans (AX), xylanase, and xylanase inhibitors have an important role in many cereal food processing applications. The effects of genotype, growing location, and their interaction (G × L) on AX, apparent xylanase activity, and apparent xylanase inhibition activity of Triticum aestivum xylanase inhibitor (TAXI) and xylanase inhibiting protein (XIP) were investigated for six hard red and six hard white spring wheat genotypes grown at three locations. Difference in total AX level among genotypes was not determined to a significant level by genotype. Instead, variability in total AX content was largely dependent on G × L. However, total AX content was significantly different between the two wheat classes. For bran xylanase activity, 25% of the variability could be attributed to G × L interaction. Moreover, there was significant difference between the bran xylanase activities in the two wheat classes. Bran TAXI activity and XIP activity were significantly different among genotypes. Genotype contributed 72% to the variability in TAXI activity and 39% in XIP. However, no significant difference was observed among the two wheat classes for TAXI or XIP activity. These results indicate that TAXI might be a stable parameter in segregating wheat genotypes with varying xylanase activity.     

Applications and limitations of tea extract as a virucidal agent to assess the role of phage predation in soils

In marine ecosystems, phage predation (phage-mediated cell lysis) is an important driver of bacterial mortality through host cell death and nutrient cycling through the release of cell contents. Both of these impacts increase marine microbial diversity by increasing interspecific competition. By contrast, very little is known about the role of phage predation in terrestrial ecosystems. A recent field study in Barrow, AK found phage predation to be a key factor controlling terrestrial bacterial population dynamics in Arctic soils. When phage abundance was artificially reduced using a tea extract, antiphage treatment, bacterial abundance, and respiration increased accordingly, suggesting top-down control by phages. The goal of this study was to examine the impact of phage predation in temperate soil ecosystems. Laboratory-scale experiments confirmed the potent antiphage properties of tea extracts. However, field experiments conducted at two discrete sites (upland and wetland) yielded little evidence that top-down control by phage predation was significant in temperate soils.     

Effects of biogas digestion of clover/grass-leys, cover crops and crop residues on nitrogen cycle and crop yield in organic stockless farming systems

The trend towards specialization in conventional farming led to large agricultural areas in Germany and in Europe lacking livestock. Also stockless organic farming has increased during recent years. In organic farming clover/grass-ley (CG) provides nitrogen (N) to the whole cropping system via symbiotic N₂ fixation and also controls certain weeds. A common practice in organic farming, when ruminants are not present, is to leave the biomass from CG in the field for their residual fertility effect. CG biomass, crop residues (CR) and cover crops (CC) represent a large unexploited energy potential. It could be used by anaerobic digestion to produce biogas. A field experiment was carried out by implementing a whole cropping system with a typical crop rotation for such farming systems on the research station Gladbacherhof from 2002 to 2005. The crop rotation consisted of six crops (two legumes and four non-legume crops). The aim was to evaluate whether the use of N could be improved by processing biomass from CG, CR and CC in a biogas digester and using the effluents as a fertilizer, compared to common practice. In the control treatment, represented by the usual stockless system, the CG, CR and CC biomass were left on the ground for green manure purposes. In the biogas systems these substrates were harvested for digestion in a biogas plant. The effluents of digestion were used to manure the non-legumes in the same crop rotation. Results indicate that digestion of CG, CR and CC can increase the crop dry matter and N yields and the N content of wheat grains in organic stockless systems. Harvesting and digestion of residues and their reallocation after digestion resulted in a better and more even allocation of N within the whole crop rotation, in a higher N input via N₂ fixation and lower N losses due to emissions and probably in a higher N availability of digested manures in comparison to the same amounts of undigested biomass.     

Twin-Screw Extrusion Processing of Feed Blends Containing Distillers Dried Grains with Solubles (DDGS)

Extrusion trials were conducted with varying levels of distillers dried grains with solubles (DDGS) along with soy flour, corn flour, fish meal, vitamin mix, mineral mix, and net protein content adjusted to 28% using a Wenger TX-52 twin-screw extruder. The properties of extrudates were studied in experiments conducted using a full-factorial design with three levels of DDGS content, two levels of moisture content, and two levels of screw speed. Increasing the DDGS content from 20 to 60% resulted in a 36.7% decrease in the radial expansion, leading to a 159 and 61.4% increase in the unit density and bulk density of the extrudates, respectively. Increasing the DDGS content resulted in a significant increase in the water absorption index (WAI) but a significant decrease in the water solubility index (WSI) of the extrudates. Changing the screw speed and moisture content had no significant effect on the radial expansion ratio but resulted in a significant difference in the bulk density of the extrudates, which may be due to the occurrence of longitudinal expansion. Even though changing the moisture content and screw speed had no significant effect on the WSI of the extrudates, significant differences in the WAI of the extrudates were observed. The ingredient components in the blend and moisture content had an influence on the color changes of the extrudates, as did the biochemical changes occurring inside the barrel during processing. Overall, it was determined that DDGS could be included at a rate of up to 60% using twin-screw extrusion, and that viable pelleted floating feeds can be produced.     

Fluoreszenzmikroskopischer Nachweis von DDT und seinen Mitteln

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