超临界CO2干燥罗非鱼片的传质模型和数值模拟

为了探讨超临界CO2干燥罗非鱼的机理,该文基于微分床的质量守恒定律建立了超临界CO2干燥罗非鱼片的传质数学模型,通过Matlab软件对其干燥过程进行了数值模拟,分析了干燥室内超临界CO2中的溶质质量分数和罗非鱼片中的溶质质量分数随干燥时间和干燥床高度变化的规律,揭示溶质在超临界CO2干燥过程中的传质模式。结果表明:在超临界CO2干燥罗非鱼片的过程中,溶质传质主要以对流扩散为主,而以轴向扩散为辅;数值模拟的结果与试验值拟合良好(R2=0.97),相对偏差的绝对值在10%以内,说明建立的传质数学模型能较好的模拟超临界CO2干燥罗非鱼片的过程。研究结果可为超临界CO2干制罗非鱼片的工业化生产的过程控制提供参考。     

Comparative study of the effects of solid-state fermentation with three filamentous fungi on the total phenolics content (TPC), flavonoids, and antioxidant activities of subfractions from oats (Avena sativa L.)

The aim of present work was to investigate the effect of solid-state fermentation with filamentous fungi (Aspergillus oryzae var. effuses, Aspergillus oryzae, and Aspergillus niger) on total phenolics content (TPC), flavonoids, and antioxidant activities of four subfractions of oat, namely, n-hexane, ethyl acetate (EA), n-butanol, and water, and compare them to their corresponding subfractions of unfermented oat. The TPC and total flavonoids increased dramatically, especially in EA subfractions (p < 0.05). The levels of antioxidant activity of subfractions were also significantly enhanced (p < 0.05). The highest antioxidant activities were also found in the EA subfractions. The polyphenols in EA were analyzed by high-performance liquid chromatography at 280 nm. Most polyphenols were increased remarkably, especially ferulic and caffeic acids. There was a clear correlation between the TPC and antioxidant activity. In conclusion, fungi fermentation is a potential bioprocess for increasing the TPC, flavonoids, and antioxidant activities of oat-based food.     

Effect of protein on the detection of fluoroquinolone residues in fish meat

Using fish serum albumin (FSA) as the model protein, molecular fluorescence spectrometry and high-performance liquid chromatography (HPLC) were applied to study the effect of protein on the extraction of fluoroquinolone (FQ) residues in fish meat. There was a strong interaction between FQs and protein through hydrogen bonds, which could be broken as protein degenerated with 60-100% (v/v) acetonitrile acid solution, and FQs bound with protein were released in various degrees. On the basis of the results, a novel sample preparation procedure loosely based on QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) methodology was developed for the determination of FQ residues in fish muscle samples, using 90% (v/v) acetonitrile acid solution as the extractant, combined with a dispersive solid-phase extraction (DSPE) cleanup step. Mean recoveries of four FQs from spiked samples at a concentration range of 50-200 ng g(-1) were 73.3-95.9% with relative standard deviations (RSD) lower than 10.7%.     

Multiresidue analysis of 58 pesticides in bean products by disposable pipet extraction (DPX) cleanup and gas chromatography-mass spectrometry determination

A method based on disposable pipet extraction (DPX) sample cleanup and gas chromatography with mass spectrometric detection by selected ion monitoring (GC/MS-SIM) was established for 58 targeted pesticide residues in soybean, mung bean, adzuki bean and black bean. Samples were extracted with acetonitrile and concentrated (nitrogen gas flow) prior to being aspirated into DPX tubes. Cleanup procedure was achieved in a simple DPX-Qg tube. Matrix-matched calibrations were analyzed, and the limits of quantification (LOQ) of this method ranged from 0.01 mg kg(-1) to 0.1 mg kg(-1) for all target compounds. Coefficients of determination of the linear ranges were between 0.9919 and 0.9998. Recoveries of fortified level 0.02 mg kg(-1) on soybean, mung bean, adzuki bean and black bean were 70.2-109.6%, 69.1-119.0%, 69.1-119.8%, and 69.0-120.8%, respectively, for all studied pesticides. Moreover, pesticide risk assessment for all the detected residues in 178 market samples at Beijing market area was conducted. A maximum 0.958% of ADI (acceptable daily intake) for NESDI (national estimated daily intake) and 55.1% of ARfD (acute reference dose) for NESTI (national estimated short-term intake) indicated low diet risk of these products.     

Competitive enzyme-linked immunoassay for sialoglycoprotein of edible bird's nest in food and cosmetics

The proliferation of fake and inferior edible bird's nest (EBN) products has recently become an increasingly serious concern. To identify and classify EBN products, a competitive enzyme-linked immunoassay (ELISA) was developed to quantitate sialoglycoprotein in EBN used in food and cosmetic applications. The characteristic sialoglycoprotein in EBN was found, extracted, purified, and analyzed. Sialoglycoprotein, considered the main carrier of sialic acid in EBN, consisted of 106 and 128 kDa proteins. A monoclonal antibody that could recognize both proteins was prepared. The heat-treated process did not change the affinity of sialoglycoprotein with the antibody. An optimized ELISA method was established with a cross-reactivity of less than 0.1% and an IC(50) of 3.3 μg/mL. On the basis of different food and cosmetic samples, the limits of detection (LOD) were 10-18 μg/g. Recoveries of fortified samples at levels of 20 and 80 μg/g ranged from 81.5 to 96.5%, respectively. The coefficients of variation were less than 8.0%.     

家蚕3-羟酰辅酶A脱氢酶基因全长cDNA克隆及其在质型多角体病毒感染家蚕的差异表达

家蚕质型多角体病毒（Bombyx mori cytoplasmic polyhedrosis virus,BmCPV）是家蚕的重要病毒病原之一,往往给养蚕业生产造成极大危害。我们以前的研究运用基因芯片技术在感染质型多角体病毒的家蚕中肠中鉴定出一个差异表达的3-羟酰辅酶A脱氢酶蛋白基因（Bombyx mori3-hydroxyacyl-CoA dehyrogenase protein gene-Bm3HAD）。本研究利用cDNA末端快速扩增技术（RACE）克隆了该基因,其全长cDNA序列为1168bp,包含一个83bp5＇端非翻译区序列（5＇-UTR）、一个930bp的开放阅读框（ORF）和一个155bp的3＇端非翻译区序列（3＇-UTR）;基因结构分析发现该基因由5个外显子和4个内含子组成。RT-PCR结果显示该基因在家蚕中肠、脂肪体、血液、丝腺及生殖体中均有表达。荧光定量PCR结果表明该基因在BmCPV感染初期为上调表达,随着病毒感染的进展,该基因的表达水平逐渐降低,并转变为下调表达。研究结果为进一步研究BmCPV对家蚕致病的分子机制提供了有益的信息。     

H5N1亚型AIVHA抗原表位的高效表达及其抗原活性分析

血凝素（hemagglutinin,HA）蛋白是禽流感病毒（avian influenza virus,AIV）的一个重要表面抗原性蛋白,在疾病诊断和防治上有重要意义。本研究为了探讨一种更为简便有效的HA重组蛋白表达途径,利用生物信息学软件,对H5N1亚型AIVHA基因编码的氨基酸序列进行分析,在分析其在大肠杆菌中的密码子偏好性、稀有密码子分布情况及有关蛋白的抗原性等重要特性后,构建了HA抗原表位重组表达质粒pET-32a（＋）-HA。经测试,该重组质粒在1mmol/LIPTG诱导剂作用下诱导过夜,能在大肠杆菌Rosetta-gami B（DE3）中高效表达,并得到48.1kD大小的目的重组表达蛋白。重组蛋白用6×His-tagged protein纯化试剂盒纯化后,与福氏佐剂等量混合制备成抗原,以200μg/鸡的剂量皮下注射2月龄SPF鸡3次,采血分离血清。Western-Blot试验结果表明,该重组表达蛋白能分别与所制备的高免鸡血清及H5N1亚型AIV阳性血清发生特异性反应,在硝酸纤维素膜上出现特异性杂交带。说明本试验研究的HA抗原重组表达蛋白具有良好的免疫原性和反应原性,保留了HA蛋白的抗原活性,提示该重组蛋白在H5亚型AIV的防治技术研究中具有重要的实际应用价值。     

大田滴灌自清洗网式过滤器水头损失试验

自清洗网式过滤器是目前国内外大田滴灌应用最广泛过滤器之一,其水头损失是评价过滤器性能的关键参数。该文通过对自清洗网式过滤器清水和浑水水头损失的试验研究,重点分析了80和120目滤网对应的清水和浑水水头损失变化规律。在清水试验中,得出了2种滤网目数对应过滤流量与水头损失变化关系式;在浑水试验中,分别研究了流量一定(220m3/h)和含沙量一定(0.190g/L)条件下水头损失随过滤时间变化规律,重点研究了这2种条件下浑水水头损失的计算方法,并对2种情况下水头损失进行了计算,对各种组合条件下浑水水头损失计算公式进行了拟合,分别得到流量一定条件下10种不同含沙量和含沙量一定条件下5种不同流量的水头损失计算公式。结果表明:各公式拟合精度较高,决定系数均大于0.95,可以用于浑水水头损失计算,研究结果可为实际工程中自清洗网式过滤器水头损失的计算提供参考。     

REDUCING NITRATE CONTENT IN LETTUCE BY PRE-HARVEST CONTINUOUS LIGHT DELIVERED BY RED AND BLUE LIGHT-EMITTING DIODES

Effect of pre-harvest continuous light with different red/blue ratio on photon flux density (R/B ratio) on reducing nitrate accumulation was studied by growing lettuce (Lactuca sativa L.) under continuous illumination delivered by light-emitting diodes (LEDs). Results show that nitrate concentration decreased by 1648.0–2061.1 mg kg^?1 in leaf blade and 962.9–2090.3 mg kg^?1 in petiole, accompanied by a dramatic increase in soluble sugar content. Compared with monochromatic red light treatment, the decrease in nitrate concentration and increase in soluble sugar content in lettuce under mixed red and blue light were more pronounced. The lowest nitrate concentration was observed in the treatment with R/B ratio of 4. It's concluded that pre-harvest exposure to 48?h continuous LED light could effectively reduce nitrate accumulation in lettuce and this process is strongly affected by R/B ratio of light. This study may provide new perspective for pre-harvest quality management of vegetable, especially in commercial leaf vegetable production under artificial lighting.     

红壤溶磷菌的筛选及溶磷机制

采用以磷酸铝为磷源的蒙金娜(PVK)液体培养基研究了从红壤土中筛选出的4种溶磷菌的溶磷效果,选出其中的优势菌株B1,并对其溶磷机理做出初步探讨。结果表明,所筛选出的4株溶磷菌在液体培养条件下均有显著的溶磷效果,其中菌株B1在培养4 d后有效溶磷量最大,达到292.8 mg L-1。各处理培养液pH在培养期间均有显著下降,pH从7.0下降至3.2~4.7。高效液相色谱测定发现,各菌株培养液中有机酸的种类与含量随培养时间变化而不同,其中菌株B1主要分泌草酸和苹果酸,培养1 d后有机酸总量可达到5 mmol L-1;通过添加有机酸对磷酸铝活化的试验表明,分泌有机酸溶磷仅是菌株B1溶磷机制之一,可能还存在其他溶磷机制。菌株B1生长的适宜pH范围为5~9,最适培养温度为30℃,100 ml三角瓶的最适装液量为30~40 ml。经鉴定,菌株B1与苏云金芽孢杆菌有99.9%的相似性。