芸薹属AC基因组中SUC基因家族的鉴定与进化分析

为分析芸薹属AC基因组中SUC基因（负责蔗糖和质子同向转运的蛋白基因）家族的扩张与丢失,基于已公布的白菜和尚未公布的甘蓝及甘蓝型油菜基因组数据对SUC基因进行全基因组鉴定,并分析基因结构域特征、生化特征、进化关系和表达特性。依据HMMER程序构建的SUC基因家族的HMM（隐马尔科夫）模型,在白菜、甘蓝、甘蓝型油菜中,各检索出12、11和24个SUC候选基因;通过用SUC家族特征进行筛选,最终各保留了12、4和7个SUC基因;通过对SUC基因在拟南芥、白菜、甘蓝和甘蓝型油菜中的系统发育分析,SUC基因家族在芸薹属物种中分成了3个亚类。利用MCscan对这4个物种基因组的共线性分析,结果表明SUC基因家族成员在芸薹属物种基因组加倍后以及白菜和甘蓝杂交形成油菜以后发生了不同程度的丢失。同时,序列生化特性预测结果表明SUC蛋白是属于偏碱性的疏水性蛋白且结构稳定;表达谱分析显示,所有SUC基因基本上在所有的组织中都有不同程度的表达;启动子分析表明,SUC基因的启动子区富含LTRE、ABRE、MYC、MYB和W-box等逆境应答相关顺式作用元件,因而该基因可能也与抗逆性相关。     

Citrus fruits. Part II. Chemistry, technology, and quality evaluation. B. Technology

In Part II of this review on citrus fruits, the literature on chemistry, technology, and quality evaluation are critically considered. Sweet oranges, mandarin, grapefruit, lemon, and lime are generally used for processing. The literature on chemical components of citrus fruit which include sugars, polysaccharides, organic acids, nitrogenous constituents and lipids; carotenoids which contribute to color; vitamins and minerals and flavonoids; limonoids, some of which impart bitterness to the juice; and the volatile components which contribute to aroma were reviewed in section A. Chilled and pasteurized juices, juice concentrates, and beverages are the important products manufactured commercially, and to a limited extent powdered citrus juices, canned segments, and marmalades. The literature on the manufacture of these products also as new types of juice and oil extractors; TASTE and other types of evaporators; tank farms to store juice and concentrate in bulk; aseptic filling in bulk containers and retail packs; alternate flexible and rigid containers other than glass and tin; and recovery of volatile flavoring constituents during juice processing are some of the important technological developments in the recent past and have been discussed in this section. Bitterness in citrus juices and its control, composition of cloud, and its stability and changes during storage have been reviewed. Essential oils, pectin, frozen and dried juice sacs, dried pulp and molasses, flavonoids, seed oil, and meal are the important byproducts, the manufacture of which is given in essential details. Generally, consumers judge the product on the basis of its sensory attributes. The quality of finished product is dependent upon the raw materials used and control of processes. In section C, the U.S. Department of Agriculture (USDA) standards for different products, physicochemical and microbiological parameters prescribed as indices of quality of fruit, juice, concentrate, and other products; composition of essential oils; and aroma concentrates are discussed in relation to sensory quality. Analytical methods for compounds affecting quality, and methods for detection of adulteration in different citrus products are briefly reviewed. The importance of sensorily evaluating quality of citrus products to select and develop quality control indices is emphasized. Areas where further research are required are indicated. A comprehensive bibliography is provided to aid further study and research.     

Antibiofilm effects of pomegranate peel extracts against B. cereus,B. subtilis,and E. faecalis

In this study, the antibacterial and antibiofilm properties of pomegranate (Punica granatum L.) extracts (PPLs) prepared by 10 g of pomegranate peels (PPL10) and 100 mL of different solvents (ethanol, methanol, and their acid combinations, and water) were investigated as sources of bioactive compounds against food-related bacteria. The antimicrobial activities of the extracts were measured by using agar well diffusion assay. The acid-treated extracts exhibited the highest antimicrobial activities (31–34 mm). The biofilm formations were assessed by using a microplate reader (570 nm) after crystal violet staining. The prevention and removal of bacterial biofilms were also evaluated by using extracts prepared by 5 g of initial pomegranate peel (PPL5) with the different solvents or 200 ppm chlorine solution. All PPL5 and PPL10 extracts diluted at different ratios inhibited and removed biofilms, and the highest antibiofilm effects were up to 80% by acid-treated extracts. In addition, PPL5s and PPL10s were as effective as or more effective than chlorine for the prevention of biofilms. Therefore, from an economical perspective the PPL5s could represent promising candidates as natural antibiofilm agents for food industry.     

The occurrence of Bacillus cereus, B. thuringiensis and B. mycoides in Chinese pasteurized full fat milk

In 2006, a total of 54 samples of pasteurized full fat milk packaged in cartons were collected in spring and in autumn from chain supermarkets in Wuhan, China. The samples were examined and enumerated by MPN methods strictly according to guidelines laid out in US FDA/CFSAN BAM Chapter 14. Among 102 isolated B. cereus-like bacteria, 92 isolates were identified to be B. cereus, 9 B. thuringiensis and 1 B. mycoides. It was found that the occurrences of B. cereus were 71.4% and 33.3% in spring and in autumn samples respectively and the average count among the positive samples was 11.7 MPN/ml. The PCR detection results revealed that the enterotoxin genes hblA, hblC, hblD, nheA, nheB and nheC occurred in B. cereus isolates with frequencies of 37.0%, 66.3%, 71.7%, 71.7%, 62.0% and 71.7% respectively. Nine B. thuringiensis isolates were also identified from six pasteurized milk samples, and most of them harbored six enterotoxic genes and the insecticidal toxin cry1A gene. The single B. mycoides isolate harbored nheA and nheC genes. The data provides information for further evaluating the effect of B. cereus-like bacteria on food safety of Chinese milk products.     

Occurrence of fumonisins B1 and B2 in asparagus from Shandong province, P.R. China

Thirty samples of asparagus spears were collected from the fields in Shandong province, China, in July 2004, and were analysed for the occurrence of fumonisins B₁ and B₂ (FB₁ and FB₂) by HPLC coupled with electrospray ionization tandem mass spectrometry. Twenty-four samples (80%) contained fumonisins, ranging from 24 to 670 ng g^-1 (average 123 ng g^-1) and 17 to 138 ng g^-1(average 35 ng g^-1) for FB₁ and FB₂, respectively. The total amount of fumonisins (FB₁ and FB₂) in all samples ranged from 47 to 714 ng g^-1 (average 158 ng g^-1) (based on dry weight). This is the first report on the natural occurrence of FB₁ and FB₂ in asparagus spears in China.     

Survey of breakfast and infant cereals for aflatoxins B1, B2, G1 and G2.

Three hundred and forty-nine breakfast and infant cereal samples were collected at retail level across Canada from 2002 to 2005. They included rice-, soy-, barley-based and mixed-grain infant cereals, corn-, wheat-, rice-based and mixed-grain breakfast cereals, and were analysed for aflatoxins B1, B2, G1 and G2 using a modified AOAC International official method. An immunoaffinity column was used for the cleanup and purification of extracts. Determination of aflatoxins was by LC using post-column derivatization with pyridinium hydrobromide perbromide and fluorescence detection. Results indicated that 50% of both breakfast and infant cereals had detectable levels (limit of detection = 0.002 ng g-1) of aflatoxin B1, which is the most toxic of the four toxins. The levels found varied from 0.002 to 1.00 ng g-1 for aflatoxin B1, from 0.002 to 0.14 ng g-1 for aflatoxin B2, from 0.008 to 0.27 ng g-1 for aflatoxin G1, and from 0.008 to 0.048 ng g-1 for aflatoxin G2. Only 4% of the breakfast cereals and 1% of the infant cereals had aflatoxin B1 levels exceeding 0.1 ng g-1, which is the European Union maximum limit for aflatoxin B1 in baby foods and processed cereal-based foods for infants and young children.     

Fumonsin B1, B2, and B3 content of commercial unprocessed maize imported into South Africa from Argentina and the USA during 1992.

The widespread occurrence of F. moniliforme and the toxic effects of its secondary metabolites, the fumonisins B1(FB1), B2(FB2) and B3(FB3), make it imperative that fumonisin contamination of maize, a major constituent of animal feed as well as the staple diet of many populations, be closely monitored to reduce the risk of fumonisin exposure. Equine leukoencephalomalacia and porcine pulmonary oedema have been associated with the intake of feed heavily contaminated with fumonisins. In addition, high levels of fumonisins in the maize-based staple diets of certain populations have been linked to a high incidence of oesophageal cancer in the Transkei region of South Africa and in Linxian and Cixian Counties, China. Bulk shipments of maize imported into South Africa from the USA and Argentina during 1992 were sampled at the port of entry to determine fumonisin levels. Of the 79 samples from two US shipments, all were positive for fumonisins, with FB1 constituting approximately 71% of the total fumonisins with an overall mean of 2.35 micrograms/gFB1. The maximum FB1 level observed was 3.9 micrograms/g. These levels contrast with those obtained from two Argentinian bulk shipments, which also were all positive for fumonisins, but had a mean FB1 level of 0.31 microgram/g and a maximum observed level of 0.7 microgram/g FB1 measured over 47 composite samples.     

Determination of water-soluble vitamins B1, B2, B6 and B12 in milk using HPLC]

Simple methods of determining the water-soluble vitamins B1, B2, B6 and B12 in milk by HPLC are described. Compared to existing procedures, the following improvements can be realized. The oxidation of vitamin B1 to thiochrome is stopped by the addition of sodium sulphite. This step significantly increases repeatability. Thiochrome is then extracted with butan-1-ol, which results in fewer co-extracts and greater selectivity. After the hydrolysis of the 5-phosphates of the vitamin B6 (pyridoxine, pyridoxal and pyridoxamine), these three vitamers are determined by isocratic HPLC as DDS-ion-pairs and with fluorimetric detection. As only microbiological methods have so far been used for the determination of minute quantities of vitamin B12 in milk, a new HPLC procedure is proposed with a detection limit of 0.2 micrograms vitamin B12/L milk.