Magnetic separations in biotechnology—a review

Magnetic separation technology has a broad range of potential applications in both small and large scale biotechnology. This review considers a selection of magnetic techniques and their possible uses.     

14C labelling of lignins of normal and bm3 maizes for fermentation studies

[U-¹⁴C] phenylalanine (phe*) and [O¹⁴CH₃] sinapic acid (sin*) were infused into the cut ends of normal and bm3 maizes (anthesis stage) under or above the last node or at mid-internode, with or without the leaf, in light or in darkness. Radioactivity was measured in the organs, and in phenolic constituents of the cell wall and saponified residues of the bases and tops of the apical inter-node. In both maize genotype labelled under the node the radioactivity was distributed more evenly in the organs with sin* than with phe*. Infusion above the node and at mid-internode greatly increased radioactivity in the bases and tops, respectively. Removal of the leaf only slightly increased the radioactivity, mainly in the bases, and no clear-cut effect of darkness was observed. Phe* labelled the phenolic acids and the three lignin units, but the syringyl units of bm3 maize were only slightly labelled. Sin* specifically labelled the syringyl units, which represented the least condensed fraction of lignins. Both the native and labelled lignins were highly alkali soluble. There were differences in lignin biogenesis between the bases and tops, and between normal and bm3 maizes. The newly formed lignins were slightly different from the native lignins but had similar types of heterogeneity, with variations in the internode and between genotypes similar to those in native lignins. Provided due allowance is made for the distinguishing characteristics of newly formed lignins, the [¹⁴C-lignin] cell walls, which are strongly labelled on complementary structures, seem suitable model substrates for fermentation studies.     

Transformations of (14C-lignin) cell walls of wheat by rumen microorganisms

The lower halves of apical internodes of wheat harvested at the flowering stage were labelled with [U-¹⁴C] phenylalanine (phe) or with [O¹⁴CH₃] sinapic acid (sin). Cell wall residues (CWR) and saponified residues (SR) were incubated in a fermenter simulating the rumen for 7 days with rumen fluid or without microorganisms (controls). PheCWR was labelled in all lignin units (measured as aldehydes from nitrobenzene oxidation), in phenolic acids and slightly in proteins. Labelling of pheSR was more lignin-specific. SinCWR and sinSR were specifically labelled in syringyl units of lignin. The fermentation of CWR resulted in phenylpropane-derived unit losses in the following decreasing order: ferulic acid>p-coumaric acid>syringaldehyde>vanillin>p-hydroxybenzaldehyde. If allowance is made for slight losses in controls, 61, 52, 61 and 63% of the phenylpropanes of pheCWR, sinCWR, pheSR and sinSR, respectively, were transformed into an acid-precipitable fraction, an acid-soluble fraction and ¹⁴CO_2. The comparison of pheCWR and sinCWR degradation showed that syringyl units were solubilised into acid-precipitable molecules to a greater extent than the other lignin units; demethylation of the syringyl units of lignins was also evident from the different productions of ¹⁴CO₂. Alkali-resistant lignins of SR were mainly transformed into acid-precipitable molecules and were weakly degraded. Lignin solubilisation and degradation seem to be governed by different mechanisms which depend on both cell wall structure and rumen microflora.     

Intrinsic isotopic C labelling of polyphenols

The intrinsic isotopic labelling of plants with ¹³CO₂ is an effective method to generate highly labelled compounds using photosynthesis and avoiding labour-intensive complex organic syntheses. In this study, the intrinsic isotopic labelling of polyphenols in parsley, spinach and peppermint is shown for the first time. The plants were grown in an atmosphere where ¹²CO₂ was replaced by ¹³CO₂, in order to generate highly labelled compounds. The total content of ¹³C as well as the individual polyphenols were analysed by Isotopic Ratio-MS and HPLC–Iontrap-MSⁿ.     

Consumer preferences for food labelling attributes: Comparing direct ranking and best–worst scaling for measurement of attribute importance,preference intensity and attribute dominance

The use of food labelling to convey information about product and process quality and for product differentiation purposes has multiplied. In order to judge the relevance attributed by consumers to such information, valid measurement methods are needed. Such methods are also needed to reveal the probabilistic nature of preference data, so that heterogeneity can be explicitly accounted for. A survey among Swedish residents (n = 506) compared attribute importance rankings for labelling of beef from two formats of best–worst scaling (BWS) with those from standard direct ranking (DR). A choice probability R–index measure was modelled to make the methodological comparison consistent. While earlier studies on labelling of beef were confirmed, BWS and DR did not concur when directly compared, even when using the R–index. BWS improved individual choice predictions compared with DR, and generated a more consistent dominance ordering of attribute importance. These findings suggest that methods used to elicit importance weights or preference ranking may violate transitivity and dominance requirements.     

香港食品营养标签修订规例应对研究

本文在深入研究香港食品营养标签修订规例的基础上,通过问卷调查、法规培训、建立平台、标签检测和设计、电子预警、现场核查等方式,建立一套科学有效的应对机制,帮助出口企业应对修订规例,确保食品贸易健康发展.     

Essential and trace elements content of commercial infant foods in the UK

There is a paucity of data in respect of the nutritional quality of complementary foods for infants and young children aged between 6 and 12 months. The primary objective of this study was to examine nutritive values of such complementary infant food on the UK market in order to ascertain their suitability relative to dietary guidelines for the 6–9 months age group. Quantitative analyses were conducted on eight different products representing four popular brands (meat and vegetable based) currently on sale in the UK. Eight major mineral and trace elements, namely: calcium, copper, magnesium, iron, zinc, potassium, sodium and selenium were measured by ICP–OES and ICP–MS. The results of these studies were referenced to the Recommended Nutrient Intake (RNI) values for 6–9 months old children, and a menu of entire daily intake of minerals and trace elements was composed taking into consideration the nutrient and energy intake from milk consumption. Based on these comparisons, all the food samples studied in this work contained less essential minerals than expected from the RNI values except for potassium in meat and vegetable based recipes. These results suggest that commercial complementary infant foods on the UK market may not contain the minimum levels of minerals required for the labelling declaration of micronutrient content (Commission Directive 2006/125/EC). This provides opportunities and scope for product optimisation to improve their nutritive value.     

郁金香杂色综合症病原的免疫电镜鉴定与检测研究

免疫胶体金标记技术的鉴定结果表明,造成郁金香杂色综合症的主要病原是ＴＢＶ,其次也有少量的植株被ＴＢＢＶ、ＴＴＢＶ及ＣＭＶ所感染。ＴＢＶ及ＴＴＢＶ病毒主要在花瓣和叶片中增殖与积累,并通过种球传给后代。ＴＢＶ和ＴＢＢＶ可共同识别某些植株的病原,说明二者应属同一种病毒的不同株系。     

Intrinsic 42Ca-Labelling of Green Bean Pods for Use in Human Bioavailability Studies

A hydroponic growth procedure which enables the intrinsic ⁴²Ca-labelling of green beans ( Phaseolus vulgaris L) has been developed. Whole-plant Ca influx was measured from planting through the period of pod expansion for a crop of 60 plants grown hydroponically in a 3m²area. Total Ca influx was 10·1mmol per plant; 35% of this influx occurred during the period of pod growth. Plants were labelled with ⁴²Ca via the nutrient solution during the period of pod expansion; isotopic composition of harvested pods was nearly identical to that of the administered solution. Recovery of isotopic tracer at harvest was as follows: pods 8·4%; leaves, 61·1%; stems, 17·1%, roots, 9·0%. Pod yield was 98·8g FW per plant. ⁴²Ca-labelled green beans can be used safely to investigate Ca bioavailability in humans.