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Thembekile NcubeRachmond L. Howard Emil K. AbotsiElbert L. Jansen van Rensburg Ignatious Ncube 《Industrial Crops and Products》2012,37(1):118-123
Jatropha curcas seed-cake was evaluated for use as a solid state fermentation substrate for production of cellulolytic and xylanolytic enzymes by Aspergillus niger. Supplementation of the seedcake with 10% thatch grass (Hyperrhaenia sp.) resulted in a fivefold increase in xylanase production. Ammonium chloride supplementation increased production of xylanase by 13%. Under the same conditions, cellulase production was not influenced by supplementation with grass or the nitrogen sources used. Maximum xylanase was produced at 25 °C whilst cellulase was maximally produced at 40 °C. Highest xylanase activity was obtained when the cultures had an initial pH of 3 whereas cellulase was maximally produced at an initial pH of 5. Under optimised conditions, 6087 U and 3974 U of xylanase and cellulase respectively were obtained per gram of substrate. Zymograms of crude enzyme extracts showed six active bands ranging from 20 kDa to 43 kDa for cellulase and a 31 kDa active band for xylanase. 相似文献
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Prediction of impact by near-infrared reflectance spectroscopy (NIRS) analysis of rodent diet preferences was evaluated in four dominant field rodents in Moravia farmland (Czech Republic). These include the common vole (Microtus arvalis), pygmy field mouse (Apodemus uralensis), wood mouse (Apodemus sylvaticus), and black-striped field mouse (Apodemus agrarius). Using fecal samples, this method predicts the proportions of food components consumed, based on a calibration equation developed through feeding tests in the laboratory. We used the wood mouse as a model species for NIRS device calibration. The two types of monofood feces collected from mice that were fed with either barley or wheat grain were mixed to form a series of increasing proportions of wheat feces subsequently measured by NIRS. Because of a good fit, the calibration equation was then applied to other mice, whereas a separate calibration equation had to be developed for the common vole. The percentage diet preferences were determined by comparing feces from preference choice tests with the calibration equation. Whereas all mice preferred wheat to barley, the common vole showed no preference for either crop. Thus proportion of wheat preference by all Apodemus sp. predict stronger impact of these in wheat fields in ripe stage than in barley one. 相似文献
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Interactions between populations of the calanoid copepod Acartia tonsa Dana and the harpacticoid copepod Tisbe holothuriae Humes in mixed cultures of live feed for fish larvae 
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下载免费PDF全文 Benni W Hansen Emil Boesen Ole B Brodnicke Natasja L Corfixen Per M Jepsen Stephanie M Larsen Casper D Læssøe Pernille S Munch Peder K F Nielsen Jørgen Olesen Bent Vismann Birgitte Nilsson 《Aquaculture Research》2018,49(3):1274-1283
Copepods are considered high quality live feed for fish larvae due to their large within species size span, swimming pattern triggering hunting behaviour, and complete biochemical profile. In a continuous cultivation system aiming at the planktonic calanoid Acartia tonsa an intruding harpacticoid frequently appears. We experimentally evaluate how the interaction from the semi‐benthic Tisbe holothuriae is affecting our cultures and ask whether the two copepod‐species are expected to pose competitive exclusion or co‐exist long‐term. This is pursued by establishing ~40 days mono‐ and mixed copepod cultures reared in a stationary setup (S) theoretically advantageous for T. holothuriae and a rotating setup (R) with organisms kept in suspension by use of a plankton wheel, theoretically advantageous for A. tonsa. The carrying capacities of A. tonsa in either mono‐ or mixed cultures are not affected whether the copepods are subject to S or R treatment. Only exception is the S‐setup containing mixed culture were A. tonsa obtains a significantly lower carrying capacity compared with A. tonsa alone in R‐setup. The mono‐ and mixed cultures of T. holothuriae are, however, highly negatively affected by the R setup compared with S setup. A long‐term solution to limit the presence of T. holothuriae is to apply turbulence level in a classical stagnant tank setup to an extend that suppress T. holothuriae and simultaneously allow algae in suspension as food for A. tonsa, make their eggs sediment as well as minimize risk of benthic‐predation on eggs. 相似文献
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Fredrik Lagergren Harry Lankreijer Jiří Kučera Emil Cienciala Meelis Mölder Anders Lindroth 《Forest Ecology and Management》2008
This study analyses the effects of thinning on stand transpiration in a typical mixed spruce and pine forest in the southern boreal zone. Studies of transpiration are important for models of water, energy and carbon exchange, and forest management, like thinning, would change those processes. Tree transpiration was measured by the tissue heat-balance sapflow technique, on a reference plot and a thinning plot situated in a 50-year-old stand in central Sweden. Sapflow was measured during one season (1998) on both plots before thinning, to establish reference values. In winter 1998/1999 24% of the basal area was removed from the thinning plot. Thinning was done so as to preserve the initial species composition and the size distribution. The measurements continued after thinning during the growing seasons of 1999 and 2000. The climate showed remarkable differences between the 3 years; 1998 was wet and cool, with frequent rain, and the soil-water content was high throughout the year. In contrast, 1999 was dry and warm, and the soil-water content decreased to very low values, ca. 5–6% by volume. In 2000, the weather was more normal, with variable conditions. Stand transpiration was similar on both plots during the year before thinning; the plot to be thinned transpired 6% more than the reference plot. After thinning, transpiration was initially ca. 40% lower on the thinned plot, but the difference diminished successively. When the following drought was at its worst, the thinned plot transpired up to seven times more than the reference plot. During the second season after thinning, the thinned plot transpired ca. 20% more than the reference plot. The increased transpiration of the thinned plot could not be attributed to environmental variables, but was most probably caused by changes in biological factors, such as a fertilization effect. 相似文献
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Cristian Paltineanu Silvia Nicolae Nicolae Tanasescu Emil Chitu Sergiu Ancu 《Erwerbs-Obstbau》2017,59(1):29-37
Plum and apple trees are the most widely spread fruit trees in south-eastern Europe. The main purpose of this paper is to characterize the spatial distribution of roots in medium and course textured soils to improve orchard management. ’Stanley’ plum cultivar grafted on Saint Julien A semi-dwarf rootstock and ’Topaz’ apple cultivar grafted on M.9 dwarf rootstock were studied in a temperate climate and medium and course textured soils. The trench technique was used. There was an intense concentration of roots near the trees and the roots did not occupy the whole soil space between tree rows. The finest tree roots in both species were prevalent. Root density was higher in tree rows versus inter-rows. Both the inter-row and in-row distances can be reduced to increase tree density if light penetration into canopy is sufficient. When a full irrigation regime is applied, a soil depth of 0.8?m would be sufficient for water application, and soil depths of 0.4 to 0.6?m would be recommended for deficit irrigation; water and fertilizers should only be applied over the surface area covering most of the roots. When a more strict control on root activity is desired, the tree roots could be cut vertically at 0.5–0.8?m distance from tree rows. The results could also be used in regions and countries with similar soil texture and climate conditions. 相似文献
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Veliyulin E Egelandsdal B Marica F Balcom BJ 《Journal of agricultural and food chemistry》2009,57(10):4091-4095
Partial (23)Na MRI invisibility in muscle foods is often referred to as an inherent drawback of the MRI technique, impairing quantitative sodium analysis. Several model samples were designed to simulate muscle foods with a broad variation in protein, fat, moisture, and salt content. (23)Na spin-echo MRI and a recently developed (23)Na SPRITE MRI approach were compared for quantitative sodium imaging, demonstrating the possibility of accurate quantitative (23)Na MRI by the latter method. Good correlations with chemically determined standards were also obtained from bulk (23)Na free induction decay (FID) and CPMG relaxation experiments on the same sample set, indicating their potential use for rapid bulk NaCl measurements. Thus, the sodium MRI invisibility is a methodological problem that can easily be circumvented by using the SPRITE MRI technique. 相似文献