It is becoming increasingly appreciated that the structure and functioning of ecological food webs are controlled by the nature and level of plant chemicals. It is hypothesized that intraspecific variation in plant chemical resistance, in which individuals of a host-plant population exhibit genetic differences in their chemical contents (called 'plant chemotypes'), may be an important determinant of variation in food web structure and functioning. We evaluated this hypothesis using field assessments and plant chemical assays in the tansy plant Tanacetum vulgare L. (Asteraceae). We examined food webs in which chemotypes of tansy plants are the resource for two specialized aphids, their predators and mutualistic ants. The density of the ant-tended aphid Metopeurum fuscoviride was significantly higher on particular chemotypes (borneol) than others. Clear chemotype preferences between predators were also detected. Aphid specialist seven-spotted ladybird beetles (Coccinella septempunctata) were more often found on camphor plants, while significantly higher numbers of the polyphagous nursery web spider (Pisaura mirabilis) were observed on borneol plants. The analysis of plant chemotype effects on the arthropod community clearly demonstrates a range of possible outcomes between plant-aphid-predator networks. The findings help to offer a deeper insight into how one important factor--plant chemical content--influences which species coexist within a food web on a particular host plant and the nature of their trophic linkages.
Field assessments and genetic analyses on tansy aphid, Metopeurum fuscoviride Stroyan were made aiming to investigate whether a specialist aphid species and its associated predator density differ between chemotypes of the plant host, tansy, and whether the essential oil composition of the plant host determines the genetic differences observed between colonies of M. fuscoviride inhabiting these different chemotypes. Tansy plants were defined after volatile extractions as Camphor Pure and Borneol Pure, respectively, with hybrid chemotypes defined as Camphor Hybrid, Borneol Hybrid, and Thujone Hybrid, respectively. Ladybird beetles, Coccinella septempunctata (L.), clearly dominated Pure Camphor plants, whereas significantly higher numbers of the nursery web spider, Pisaura mirabilis (Clerck), were detected on Borneol Pure and Borneol Hybrid plants. Genetic analyses using five polymorphic microsatellite markers revealed that higher genetic similarity existed between M. fuscoviride aphids from Borneol Pure and Borneol Hybrid plants and between Camphor Pure and Camphor Hybrid plants, respectively, whereas a lower level of genetic similarity was seen between these aphids from Thujone Hybrid plants. Accordingly, it is possible that host plant‐adapted species can create much context‐dependency in the nature and strength of predation effects, which may in turn alter costs and benefits of host plant chemical differentiations, or even the prey genotype variations. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114, 709–719.
Abstract. Until the middle of the last century, selenium was considered to be toxic, but recently it turned out to be a micronutrient with important physiological effects, whose lack impedes the functioning of several enzymes, while in the case of a prolonged deficiency, disease processes can also occur in the body. Hungary belongs to the selenium-deficient regions in Europe; therefore, our aim was to contribute to the improvement of selenium supply of the population through increasing the selenium content of milk and dairy products. A daily supplementation of 1-6 mg organic selenium to the feed of dairy cows increases the selenium content of milk from the value of 18 μg/kg to 94 μg/kg in 8 weeks, decreasing again to the initial value in 6 weeks after stopping the supplementation.After producing various products from the control milk (18 μg/kg selenium content) and the selenium-enriched milk (53 μg/kg) obtained from dairy cattle fed on a feed supplemented with 2 mg selenium/day, we concluded that the selenium content of selenium-enriched milk compared to the products produced from the control milk increased from the value of 18.6 to 58.5 μg/kg in the case of yogurt, from 66.0 to 138.1 μg/kg in the case of telemea, from 80.8 to 163.7 μg/kg in the case of orda (urdȃ) and from 88.6 to 200.0 μg/kg in the case of semi-hard cheese obtained by mixed-coagulation. The selenium content of whey also increased significantly (from 8.8-9.7 μg/kg to 20.1-25.8 μg/kg), which could also be used as a food for people or feed for animals. According to our calculations, the selenium requirements of the developing organism could be satisfied by the consumption of 2-3 dl selenium-enriched milk until the age of 8 and with 4-6 dl selenium-enriched milk until the age of 20.
The addition of synthetic CLA is a possible way in order to compose foods enriched with conjugated linoleic acids (CLAs). The most environmental friendly methods for CLA synthesis are based on microbial biosynthesis. With homogeneous catalysis using organometallic catalysts (Ru and Rh complexes) high (approximately 80%) yields were obtained with high selectivity related to bioactive isomers. The heterogeneous catalysis has the advantage that at the end of the reaction there is no need for a supplementary separation operation or recycling of the catalyst. In heterogeneous process, the maximum yield may even be higher than 90% and the selectivity remains quite high as the reaction conditions are optimized. The substrates for obtaining CLAs are, in general, linoleic acid or alkyl linoleates and the catalysis is acidic. The yield and the selectivity depend on the strength and the type of acidic sites, as well as on the size distribution of the particles. Beside the existing catalytic methods, a photocatalytic process with UV and visible light irradiation with iodine promoter can be applied.Keywords: conjugated linoleic acid, CLA, homogeneous catalysis, heterogeneous catalysis, photocatalytic process Recently many new health-benefi t effects of the conjugated linoleic acids (CLAs) were discovered. They decrease the body fat quantity and increase muscle mass, possess antiinfl ammatory and cancer preventive effects, exert benefi cial effects on the skeletal system, act as immunostimulants, and decrease the probability of asthma occurrence (HA et al., 1989;PARIZA et al., 2001).Theoretically 56 isomers exist, however, few of them (cis(c)-9,trans(t)-11; t-10,c-12-and t-9,t-11 CLA) have been shown to have signifi cant biologic activity. The bioactivity of the c-9,t-11 CLA isomer (Fig. 1) was discovered two decades ago (HA et al., 1989) and this isomer is predominant in the natural products used as foods. The main foods rich in CLA are milk, dairy products, meat and fat of the ruminants, as this isomer is produced by the bacteria of the rumen microfl ora.Nowadays, CLAs are obtained for industrial purpose from vegetable oils that are processed at high temperature (PHILIPPAERTS et al., 2011). The basic method in the industrial approach is the isomerisation of linoleic acid (LA) with basic catalysis by which the amounts of the two formed isomers (c-9,t-11 and t-10,c-12 CLA) are almost equal, and the yield is quite high. This synthetic method cannot be applied for the direct transformation of vegetable oils into CLA-rich triacylglycerols, because ester bonds of triacylglycerols hydrolyze to free fatty acids (or salts) and glycerol.
The production of heavily hopped beers, such as Indian Pale Ale (IPA) styles, has been gaining momentum in recent years in the Central European markets. To this end, the dry hopping process is becoming increasingly popular, mostly in microbreweries, but also with larger manufacturers. In our research, we investigated the dissolution rate of the main volatile component of hops, β-myrcene with a modified dry hopping method. Following the primary fermentation, we applied the dry hopping process, where the weighed hops were chopped and blended into a container with 0.5 L of beer and later added to the young beer. During the dry hopping process, we determined various important parameters of the beer, and we repeated the same measurements for the bottled beer. In the first 96 h of the dry hopping process, we monitored the concentration of β-myrcene so that we managed to determine the dissolution rate constant (k = 0.1946 h−1). The β-myrcene concentration stabilizes after 44 h in the fermenter. At the same time, measurements were conducted for bitterness, pH, CO2 and alcohol content, extract and density during the process. Our experiment demonstrates that a new method of dry hopping provides a much higher concentration of β-myrcene (215 μg/L) than other methods indicated in former studies in the field. A health and safety assessment of β-myrcene was also made and we determined what the safe amount of β-myrcene ingested with IPA beer is. Our modified process was successful, we were able to determine the dissolution rate of β-myrcene, and the recommended daily intake of IPA beer with particular reference to β-myrcene.
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