Detoxification of zearalenone and ochratoxin A by ozone and quality evaluation of ozonised corn

Zearalenone (ZEN) and ochratoxin A (OTA) are secondary toxic metabolites of fungi that can contaminate a wide range of food and feedstuff. In this study, the effects of ozone treatment on ZEN and OTA and the quality of ozonised corn are investigated. Ozone significantly affects ZEN and OTA solutions. ZEN was undetectable 5 s after being treated with 10 mg l^–1 ozone. However, OTA was resistant to ozonation with a degradation rate of 65.4% after 120 s of treatment. Moreover, ZEN and OTA solutions were difficult to degrade after being dried by a nitrogen stream. Results showed that ozone effectively degraded ZEN and OTA in corn. The degradation rates of ZEN and OTA in corn increased with ozone concentration and treatment time. The degradation of ZEN and OTA at different ozone concentrations appropriately conformed to first-order kinetics with an R² value > 0.8749. Furthermore, under the same conditions, corn with increased moisture content (MC) (19.6%) was more sensitive to ozone than corn with a low MC (14.1%). When treated with 100 mg l^–1 ozone for 180 min, ZEN and OTA in corn with 19.6% MC decreased by 90.7% and 70.7%, respectively. To evaluate the quality of ozonised corn, subsequent quality experiments were conducted using corn samples treated at different times with 100 mg l^–1 ozone. The MC of corn decreased after ozone treatment. The whiteness and yellowness of the corn increased and decreased with increasing time, respectively. The fatty acid value of the corn increased significantly (p ≤ 0.05) after 180 min of treatment. This study verified that ozone can effectively degrade ZEN and OTA in corn, but slightly affected corn quality.     

丛毛红曲菌固态发酵山药产莫纳可林K的影响因素研究

该研究以新鲜山药为发酵基质,采用丛毛红曲菌（Monascus pilosus）MS-1固态发酵山药,探究新鲜山药、干山药、山药品种、蔗糖、山药块茎大小、乳酸等因素分别对发酵山药中莫纳可林K（MK）产量的影响。结果表明,新鲜山药更有利产生MK,当发酵基质为新鲜铁棍山药,蔗糖添加量为3%,山药块茎大小为（0.5 cm×0.5 cm×0.5 cm）,乳酸添加量为0.3%时,MK产量可达8.10 mg/g。该研究可为山药的精深加工提供新思路,对新型红曲产品的开发也具有一定的借鉴意义。     

Comparison of Two DNA Aptamers for Dopamine Using Homogeneous Binding Assays

Dopamine is an essential neurotransmitter and its detection is important for bioanalytical chemistry. Two very different DNA aptamers have been reported for dopamine, one derived from an RNA aptamer (named Apt1) and other obtained via direct aptamer selection (named Apt2). In this study, we used four homogeneous binding assays to compare these two DNA dopamine aptamers. Thiazole orange (TO) fluorescence assay indicated that the Apt2 specifically bound with dopamine with a K_d of 2.37 μM, which was consistent with that from the isothermal titration calorimetry (ITC) assay. However, Apt1 had much less TO fluorescence change and also no signal from ITC. By labeling the two ends of the two aptamers by a fluorophore and a quencher, the aptamer beacons showed binding of dopamine only for Apt2. Finally, the label-free AuNP-based colorimetric assay showed no difference between these two aptamer sequences, and even non-binding random DNA showed the same response, indicating that AuNPs were not a good probe for detecting dopamine. According to the data, Apt1 does not appear to be able to bind dopamine specifically, while Apt2 showed specific binding and could be used for developing related biosensors.     

Effects of electron beam irradiation on storability of brown and milled rice

The effects of electron beam irradiation (EBI) treatment on the freshness and quality of brown and milled rice at different irradiation doses were investigated. The colors of brown rice (P > 0.05) and milled rice (P < 0.05) slightly changed after 5 kGy irradiation. After irradiation, the viscosities and amylose contents of the samples decreased (P < 0.05), crystal forms remained unchanged, but crystallinities decreased (P < 0.05). The microstructures of the samples did not change according to the results of the scanning electron microscopy. During the 120-day storage process, the free fatty acids of the irradiated samples increased at a slower rate than the non-irradiated samples did. Lipase activity was inhibited effectively, and the total viable bacterial count was significantly reduced (P < 0.05). Results indicated the potential of EBI to improve the quality and extend the shelf lives of brown and milled rice during storage.     

不同月份香椿不同部位叶片提取物中α-葡萄糖苷酶抑制剂的分布规律及其降血糖活性

为探究不同月份香椿不同部位叶片提取物中α-葡萄糖苷酶抑制剂的分布规律和降血糖效果,2020年8～11月,从3棵香椿树中采集36个样本,φ=50%乙醇提取α-葡萄糖苷酶抑制剂。分析香椿叶提取物对α-葡萄糖苷酶的抑制活性、酶抑制动力学和荧光光谱特征。进而将不同浓度香椿叶提取物与质量分数为3%葡萄糖共暴露斑马鱼,研究在斑马鱼体内的降血糖效果。结果表明：香椿叶中α-葡萄糖苷酶抑制剂的时间分布规律为8月、11月抑制率较高,可达99%;空间分布规律为从上层到下层抑制率依次递减,α-葡萄糖苷酶的抑制活性在时间和空间呈现显著性差异。香椿叶提取物对α-葡萄糖苷酶抑制的IC50为0.45 mg/mL,远低于阳性对照阿卡波糖5.05 mg/mL。香椿叶提取物的酶抑制类型为竞争性抑制,香椿叶提取物与酶的相互作用模式属于动态荧光猝灭。当香椿叶提取物暴露浓度为4 mg/L时,斑马鱼体内血糖浓度与高糖组有显著性差异。该研究为从香椿叶中大量提取α-葡萄糖苷酶抑制的采样方法设计及开发一种新型降血糖药物提供理论支持。     

我国食源性诺如病毒GII.2[P2]型毒株基因组结构与衣壳蛋白功能研究

食源性诺如病毒（Norovirus）是引起全球食品安全事件的主要微生物病原,具有丰富的遗传多样性,基因型较复杂,近年来GII.2逐渐成为我国主要流行基因型之一。为了解食源性诺如病毒GII.2型变异特点,该研究以2015年在广州地区检出的GII.2[P2]型GZ2015-L335毒株为对象,对其基因组结构及衣壳蛋白功能进行了系统表征。该毒株基因全长为7 496 bp,在线基因分型结果表明其为GII.2[P2]基因型。通过克隆其衣壳蛋白VP1基因,借助杆状病毒表达系统获取重组VP1蛋白,并采用氯化铯密度梯度离心法进行纯化。SDS-PAGE和Western blot实验结果表明重组VP1蛋白分子量约为58 ku;透射电镜结果显示该蛋白可自组装形成直径约为30 nm的病毒样颗粒（Virus-like Particle,VLP）;ELISA结果显示该VLP与抗GII.2[P]衣壳P颗粒血清具有较高结合活性。此外,受体结合实验证实该VLP与A/B/O等分泌型及非分泌型唾液呈现出广泛的结合作用。该研究对GII.2[P2]型GZ2015-L335毒株基因组结构进行了系统分析,成功制备并表征了其病毒样颗粒,结果将为食源性诺如病毒的高效抗体研制及新型检测技术研发提供支撑。     

基于核酸适配体的微囊藻毒素LR纳米金生物传感检测方法的建立及其识别机制研究

目的建立微囊藻毒素-LR(microcystin-LR, MC-LR)的纳米金生物传感比色检测法,并探究核酸适配体截短后对此方法检测效果的影响。方法采用柠檬酸钠还原法制备纳米金,通过优化盐浓度、适配体浓度、适配体与MC-LR的反应时间,建立了MC-LR的纳米金生物传感比色检测法。然后,采用组合型核酸适配体截短策略,探究了截短后的核酸适配体对比色法检测MC-LR的影响。结果 NaCl浓度为0.9mol/L,适配体浓度为0.4μmol/L, MC-LR与核酸适配体的反应时间为10 min时为其最适检测条件。在最适条件下,该方法的目测最低检测限为0.4μg/mL,仪器读数最低检测限为(1.05±0.002)ng/mL,线性检测范围为0～1.1μg/m L。探究得出核酸适配体截短后会影响其对MC-LR的识别活性。结论该方法简单、易行,线性检测范围宽,为小分子危害物核酸适配体的快速鉴定奠定了理论基础,同时,对截短核酸适配体与小分子危害物的识别活性研究提供了技术支撑。     

紫外-化学诱变筛选高产莫纳可林K或色素的红曲菌株

为获取能稳定高产莫纳可林K（MK）或红曲色素（MPs）的红曲菌株,以不产桔霉素的丛毛红曲菌（Monascus pilosus）MS-1为 出发菌株,经紫外诱变、氯化锂化学诱变及紫外-氯化锂复合诱变分别得到红曲菌11株、2株和3株,对16株诱变菌进行复筛和遗传稳 定性试验研究,得到4株产MPs或MK能力提高且遗传稳定性较好的诱变菌株。 其中诱变菌株ZWS5产MPs总色价为1 476.25 U/g,与出 发菌株MS-1相比产MPs能力提高了23.36%;诱变菌株ZWN2、LHL1和FH2的MK产量分别为7.34 mg/g、7.03 mg/g、和7.16 mg/g,比出发 菌株MS-1产MK能力分别提高了27.65%、22.26%和24.52%。