Identification of FadT as a Novel Quorum Quenching Enzyme for the Degradation of Diffusible Signal Factor in Cupriavidus pinatubonensis Strain HN-2

Quorum sensing (QS) is a microbial cell–cell communication mechanism and plays an important role in bacterial infections. QS-mediated bacterial infections can be blocked through quorum quenching (QQ), which hampers signal accumulation, recognition, and communication. The pathogenicity of numerous bacteria, including Xanthomonas campestris pv. campestris (Xcc), is regulated by diffusible signal factor (DSF), a well-known fatty acid signaling molecule of QS. Cupriavidus pinatubonensis HN-2 could substantially attenuate the infection of XCC through QQ by degrading DSF. The QQ mechanism in strain HN-2, on the other hand, is yet to be known. To understand the molecular mechanism of QQ in strain HN-2, we used whole-genome sequencing and comparative genomics studies. We discovered that the fadT gene encodes acyl-CoA dehydrogenase as a novel QQ enzyme. The results of site-directed mutagenesis demonstrated the requirement of fadT gene for DSF degradation in strain HN-2. Purified FadT exhibited high enzymatic activity and outstanding stability over a broad pH and temperature range with maximal activity at pH 7.0 and 35 °C. No cofactors were required for FadT enzyme activity. The enzyme showed a strong ability to degrade DSF. Furthermore, the expression of fadT in Xcc results in a significant reduction in the pathogenicity in host plants, such as Chinese cabbage, radish, and pakchoi. Taken together, our results identified a novel DSF-degrading enzyme, FadT, in C. pinatubonensis HN-2, which suggests its potential use in the biological control of DSF-mediated pathogens.     

Characterisation of odour‐active compounds in lupin flour

BACKGROUND: Lupin ingredients are promising alternatives to soybean products owing to their similarly high protein content. Lupin flour exhibits a green and bean‐like off‐flavour in higher amounts. The aim of this study was to characterise and identify the main odour‐active compounds in lupin flour. RESULTS: The orthonasal aroma of lupin flour was evaluated by means of aroma profile analysis and was found to be characterised by grassy‐green, metallic, fatty, fruity, hay‐like, cheese‐like, and meat‐like odour qualities. Volatile compounds of lupin flour of Lupinus angustifolius cv. Boregine were extracted with dichloromethane and isolated by solvent‐assisted flavour evaporation. Aroma extract dilution analysis (AEDA) was carried out with the obtained extract. In total, 50 odorants were detected by high‐resolution gas chromatography–olfactometry. AEDA revealed 26 odour‐active compounds with flavour dilution factors higher or equal to 32. The substances were unequivocally identified by their odour characteristics, their retention indices and their mass spectra using one‐dimensional or two‐dimensional gas chromatography–mass spectrometry, respectively. CONCLUSION: A series of unsaturated and saturated aldehydes, ketones, carboxylic acids, alkyl‐methoxypyrazines and terpenes were identified for the first time as odour‐active contributors to the aroma of lupin flour. Copyright © 2009 Society of Chemical Industry     

农杆菌介导法获得抗病毒病转基因大白菜

为获得抗芜菁花叶病毒病的大白菜植株,用携带TuMV-cp基因的农杆菌R1000和EHA105转化大白菜子叶和下胚轴,PCR、PCR-Southern检测证实TuMV-cp基因已导入并整合到大白菜的基因组中.RT-PCR检测表明TuMV-cp在转录水平上获得了稳定表达.TuMV-cp基因在转基因植株T1代中获得了稳定的遗传.抗病性鉴定结果表明转基因植株T1代较非转基因植株对TuMV的抗性增强,获得了抗病毒病的转基因大白菜植株.     

Physicochemical Characteristics and Technological Properties of Lupinus mutabilis Oil

The aim of the presented study is to examine the physicochemical parameters of the lipids present in Lupinus mutabilis seed and to compare the results with the available data for other commonly used vegetable oils. The oil quality indexes, oxidative stability index (OSI), and melting characteristics are examined. Andean lupin oil has remarkably high oxidative stability (OSI = 65 h) comparable to high-oleic oils counterparts. Quality parameters meet commonly accepted standards, including peroxide value (3.95 meq O₂ kg⁻¹) and p-anisidine value (1.25). The acid number value is 1.85 mg KOH g⁻¹. The iodine value is 110.27 g/100 g, while the enthalpy required to increase the temperature of the sample from −60 to 80 °C is equal to 57.41 kJ kg⁻¹. The beginning of the melting event (T_onset) and the phase transition temperature (T_peak) values for L. mutabilis seed oil are −29.46 and −22.63 °C, respectively. The presented results indicate the unusually high oxidative stability of the oil obtained from L. mutabilis seeds, which opens up a whole spectrum of application possibilities, e.g., designing blends with other commonly used vegetable oils to enhance their low stability. Practical Applications: The presented results provide insight into physicochemical parameters of the lipid fraction isolated from Lupinus mutabilis seeds. Andean lupin oil has very high oxidative stability, comparable to high-oleic rapeseed and sunflower oils. Therefore, the identified potential use of the studied oils is, e.g. an additive that can increase the stability of commercial vegetable oils characterized by much lower oxidative stability.     

Interaction of Lupinus angustifolius L. α and γ conglutins with 13-hydroperoxide-11,9-octadecadienoic acid

Food proteins suffer losses of functional and nutritional value due to reaction with lipid peroxidation products. The seed globulins conglutin α and γ from Lupinus angustifolius L. have been incubated with 13-hydroperoxide-11,9-octadecadienoic acid at pH 9 as a model of the interactions between seed storage proteins and lipid peroxidation products during storage and processing of protein-based products. The incubation lead to fragmentation and/or polymerization of the conglutins as determined by chromatographic and electrophoretic analysis. Losses of tryptophan, methionine, cysteine, proline, valine and leucine were shown by amino acid analysis. In vitro digestibility assays did not show clear differences between the digestibilities of the native conglutins before and after incubation with the hydroperoxide. Nevertheless, it is concluded that reaction with 13-hydroperoxide-11,9-octadecadienoic acid lead to a decrease in the nutritional value of the conglutins because the losses of essential amino acids were substantial. In addition, fragmentation and polymerization reactions most likely have a detrimental effect in the functional properties of the conglutins. These results highlight the deleterious effects that lipid peroxidation products have on products such as protein concentrates, isolates and hydrolysates obtained from lipid-rich seeds.     

Primary structure of 2S albumin from seeds of Lupinus cosentinii

 The 2S albumin from seeds of Lupinus cosentinii Guss. was purified, and the complete amino acid sequences of the dominating small and large subunit were determined by automated Edman degradation of the reduced and S-pyridylethylated polypeptides and of their enzymatic fragments. The small subunit of the 2S albumin consists of 35 amino acid residues resulting in a molecular mass (M _r) of 4233. The large subunit contains 73 amino acid residues (M _r = 8627). The two polypeptide chains are linked by two interchain disulphide bonds. In addition, the large polypeptide contains two intrachain disulphide bridges and one free sulphydryl group. A high degree of homology (88–89%) exists between the primary structure of the 2S albumin from L. cosentinii and those from other Lupinus species. The positions of the cysteines and of some other amino acids are conserved not only in most of the Dicotyledoneae 2S albumins sequenced so far but also in other storage proteins. Received: 26 May 1997     

Protein extraction from lupin seeds: a mathematical model

The effect of particle size and microstructural modification on protein extraction from defatted lupin was studied. Particles of different sizes (128–1425 μm) from untreated (control), flaked and exploded samples were extracted at pH 8.0–8.5 and different temperatures. A three-parameter kinetic model as well as a diffusional model were fitted to data. The yield of protein from the surface of particles, and the total extracted protein yield increased as particle size decreased, while the first order rate constant increased slightly or remained constant. Diffusion coefficients varied between 0.5 and 4.5x10⁻¹² m² s⁻¹ and were higher in exploded and flaked material than in the control. The energy of activation for diffusion was 43 kJ mol⁻¹. Differences in microstructure were studied by scanning electron microscopy.     

不同栽培方式对鸡毛菜贮藏保鲜品质的影响

目的 探究不同栽培方式(土壤栽培、营养液栽培、基质栽培)对鸡毛菜保鲜品质的影响。方法 采用理化分析、感官评定和多指标GSI(general stability index)综合分析方法, 测定了含水量、叶绿素、维生素C、硝态氮等品质指标。结果 不同的栽培方式对鸡毛菜营养品质和保鲜指标存在不同的影响; 土壤栽培方式下, 硝酸盐含量远远高于其他两种栽培方式。结论 无土栽培的鸡毛菜营养品质优于土壤栽培; 随着贮藏时间的延长, 鸡毛菜的品质逐渐衰退, 在4 ℃的低温贮藏条件下, 适宜的保质期为5天。     

The fatty acid composition of the oil from Lupinus albus cv. Luxe as affected by environmental and agricultural factors

There is a growing interest in white lupin (Lupinus albus L.) seed for food or feed, favoured by the availability of well-performing varieties with low content of alkaloids. The objective of this study was to assess the influence of the environmental and agricultural factors on the content and fatty acid composition of lupin oil. The investigation was performed on the sweet variety Luxe grown in three Italian locations (one continental and two Mediterranean) and 13 environments in total. Statistical analyses (analysis of variance and principal component analysis) indicated that oil content and composition of fatty acids were affected largely by the growing location. Mediterranean sites tended to lower crop yield, but to increase oil content and absolute α-linolenic acid content compared to the continental location; large variation occurred also between the Mediterranean sites. The α-linolenic acid content ranged from 1.41 to 3.24 mg/g flour, highlighting the possible value of white lupin in order to reach the recommended daily intake of this fatty acid. The observed ω-3/ω-6 ratio, ranging from 0.45 to 0.63, was much higher than that of most vegetable oils.