银耳及其伴生菌营养生理生态研究

本文分析了银耳与其伴生菌在木屑培养基和废棉渣培养基上生长期间,栽培基质中主要成分的降解规律及其有关的酶学基础。试图从营养生理角度探讨银耳与其伴生菌之间的生态关系。实验结果表明,银耳菌单独在木质纤维素上生长时,不能形成子实体。当银耳与伴生菌生长在一起时,银耳菌在木质纤维废物上生长发育良好,可形成子实体。银耳子实体生长对培养基中的纤维素降解有促进作用。     

不同化学物质对银耳孢子细胞膜通透性影响

为了提高外源基因表达胞外分泌水平,本研究通过测定不同化学物质对银耳孢子转化子细胞生物量、培养液电导率及胞外漆酶酶活的影响,探索不同化学物质对银耳孢子细胞膜通透性的影响。结果表明,浓度分别为1%、0.3%、0.2%和0.1%的二甲基亚砜、triton X‐100、氯化钾、两性霉素B均可显著提高电导率;同时银耳孢子胞外漆酶酶活分别提高至7.00U/L、6.67U/L、5.00U/L和5.00U/L,与对照达到显著差异。而表面活性剂(SDS)及有机溶剂(甲苯、戊二醛)则不利于银耳孢子的生长及漆酶的分泌。该研究结果显示,添加一定的化学物质对促进目标产物的外泌有较为明显的作用,这将为银耳孢子作为生物反应器高效表达外源基因提供科学依据。     

壳聚糖生姜精油涂膜对鲜银耳活性氧代谢和组织超微结构的影响

为探讨壳聚糖生姜精油涂膜保鲜处理对采后鲜银耳活性氧代谢的影响,用浓度为1.0%壳聚糖-生姜精油处理新鲜银耳,测定其对鲜银耳抗病性及活性氧代谢的影响。结果表明,壳聚糖生姜精油处理显著降低鲜银耳发病率及病情指数(P0.05);涂膜处理可在贮藏前期促进O■含量升高,并提高PPO、CAT和SOD活性,抑制POD活性。说明壳聚糖-生姜精油涂膜处理可以诱导银耳体内活性氧爆发,加速银耳体内活性氧清除反应,增强银耳抗病性,延缓鲜银耳采后成熟衰老。超微结构观察表明,壳聚糖-生姜精油成膜液形成致密的网状结构,附着在银耳表面,填充了银耳菌丝细胞空隙,隔绝外界微生物的侵染,防止鲜银耳水分及营养成分流失。     

银耳菌糠黑色素的理化性质及抗氧化和抑菌活性

银耳菌糠中存在一种银耳的伴生菌——炭团菌(俗称香灰菌),其菌丝生长到一定阶段后会产生大量的黑色素,具有广泛的应用价值。本研究从银耳菌糠中提取黑色素,研究其理化性质、抗氧化活性及抑菌作用。通过紫外-可见光谱、傅里叶红外光谱对提取的黑色素进行鉴定,表明银耳菌糠黑色素具有黑色素的典型特征。通过对银耳菌糠黑色素理化性质的研究,表明银耳菌糠黑色素是一种趋于黑色并略带红色和黄色的粉末;该黑色素易溶于碱性溶液;具有较好的热稳定性和光稳定性,其稳定性受氧化剂和还原剂的影响较小,受Ca²⁺、Cu²⁺的影响较明显。通过总抗氧化能力(FRAP法)、自由基清除能力检测银耳菌糠黑色素的抗氧化活性,研究表明黑色素具有较高的抗氧化活性,羟自由基、ABTS自由基清除的EC₅₀值分别为0.429 mg/mL和0.016 mg/mL。本研究还检测了黑色素对革兰氏阳性、革兰氏阴性细菌的抑菌能力,结果表明该黑色素在浓度为3.2 mg/mL时对供试菌株的抑菌率超过90%,且对革兰氏阳性菌会较敏感。本研究为银耳菌糠的有效利用及其黑色素产品的开发提供了理论基础,具有较高的经济价值。     

银耳羽毛状菌丝在松、杉、樟及混合阔叶杂木木屑培养基上的生长

在银耳的生活史中,人们发现银耳的生长、发育、繁殖都与其伴生菌—羽毛状菌丝(又称香灰菌丝)分不开。为了从多方面探明银耳羽毛状菌丝的生物学特性,我们用松、杉、樟、混合阔叶杂木的木屑培养基进行分别培养,对羽     

壳聚糖对新鲜银耳保鲜及活性氧代谢影响研究北大核心CSCD

本研究探讨壳聚糖对鲜银耳保鲜效果及活性氧代谢的影响。用浓度为0.3%壳聚糖处理新鲜银耳,实验结果显示,壳聚糖处理显著降低鲜银耳病情指数(P<0.05),在贮藏前期诱导O-·2、H2O2及ASA含量升高,诱导提高PPO、CAT、SOD、APX、PPO活性,抑制POD活性上升。说明壳聚糖处理可以诱导银耳体内活性氧爆发,加速了银耳体内活性氧清除反应;增强银耳体内抗病性,延缓鲜银耳采后成熟衰老。     

壳聚糖对新鲜银耳保鲜及活性氧代谢影响研究

本研究探讨壳聚糖对鲜银耳保鲜效果及活性氧代谢的影响。用浓度为0.3%壳聚糖处理新鲜银耳,实验结果显示,壳聚糖处理显著降低鲜银耳病情指数(P0.05),在贮藏前期诱导O-·2、H2O2及ASA含量升高,诱导提高PPO、CAT、SOD、APX、PPO活性,抑制POD活性上升。说明壳聚糖处理可以诱导银耳体内活性氧爆发,加速了银耳体内活性氧清除反应;增强银耳体内抗病性,延缓鲜银耳采后成熟衰老。     

银耳红外辐射干燥特性研究及动力学模型构建

利用红外辐射干燥技术,对银耳红外辐射干燥特性及其动力学模型进行研究,探讨不同干燥温度(60~140℃)、辐射强度(1~5 W/cm2)、空气流速(0.5~1.5 m/s)等因素对银耳失水特性的影响。结果发现,干燥温度和辐射强度对银耳失水特性影响显著,而空气流速对其影响较小。根据试验数据建立银耳红外辐射干燥的水分比与干燥时间关系的动力学模型,并对模型进行拟合检验,结果发现Midilli模型能准确的描述银耳红外辐射干燥过程,该模型预测值与实测值拟合良好。该模型可以准确预测银耳在红外辐射干燥过程中的失水特性。     

自生固氮菌的生态分布及其对农药抗性的研究

将不同地点的土样均匀地撒在无氮培养基平板上,分离并鉴定自生固氮菌。同时采用抑菌圈法和分光光度计测透光率的方法,检测6种常用的田间农药对自生固氮菌的生长影响;还运用茚三酮显色反应检测农药对自生固氮菌固氮效果的影响。结果表明,不同农药及其不同浓度对自生固氮菌生长及固氮量的影响有所不同。为添加固氮菌以提高农作物产量,监测固氮菌含量来评估作物产量,以及田间正确使用农药提供了理论依据。     

敌百虫对中肋骨条藻生长的影响

研究了有机磷农药敌百虫对中肋骨条藻Skeletonema costatum生长的影响。相对于水生甲壳类和鱼类,敌百虫对中肋骨条藻毒性较低,72 h半抑制浓度(EC₅₀)为84.8 mg/L。在31 d的亚慢性暴露下,低浓度组(≤10 mg/L)藻细胞生长趋势与对照组相似;50 mg/L的敌百虫在暴露初期对骨条藻的生长具有明显抑制作用,但在暴露15 d后,该浓度组藻细胞密度仍保持增长,最大细胞密度为2.77×10⁷ cells/mL,是对照组的137.7%。100 mg/L则能完全抑制藻细胞的生长。本实验结果说明敌百虫等有机磷农药的广泛使用可能会刺激浮游植物的生长,从而增加引发赤潮的风险。     

Challenges and Research Needs for Risk Assessment of Pesticides for Registration in Africa

Risk assessment is necessary for registration and risk management of new pesticides. The aim of this article is to discuss challenges that risk assessors in Africa face when conducting risk assessment of pesticides. Risk assessment requires toxicity assessment, environmental fate studies, and the use of models for occupational, dietary, residential, and environmental exposure assessments. Toxicity studies are very costly with the result that toxicity data used to register pesticides in Africa are often sourced from northern hemisphere countries. Assessors also often use exposure modeling results from the northern hemisphere. This is not an ideal approach as occupational exposure is influenced by agricultural practices, climatic conditions, and other factors. Furthermore, residential exposure models require time-location-activity information, exposure factors, and toxicokinetic rate constants for particular pesticides. Dietary exposure assessment needs accurate and comprehensive local food consumption data. Authorities in African countries should therefore generate the required data, despite these being very costly and tedious. Authorities should also provide guidance on the type of models and standard scenarios for estimating predicted environmental concentrations in various environmental compartments. It is recommended that higher educational institutions in Africa should incorporate risk assessment in general and pesticide toxicity and exposure models in particular in their curricula.     

Risk assessment of oncogenic potency of pesticide residues in fruits and vegetables

Pesticides are used in agriculture to improve food security by assuring good harvest, however, they can have harmful effects in human beings and animals. One of the harmful effects of pesticides is their carcinogenicity. Exposure to oncogenic compounds may result in cancer to the exposed animal or person. In this paper, exposure assessment of oncogenic potency of pesticides was performed from raw and processed fruits and vegetables. The oncogenic risk was calculated by multiplying the estimated daily intake (EDI) of the pesticide residue with the oncogenic potency factor (Q*) of the concerned pesticide. The total potential oncogenic risk was calculated to be 2.76 x 10(-3) before processing and 8.97 x 10(-4) after processing. The risk was higher than the EPA acceptable limit of 1 x10(-6). Despite the calculated levels exceeding the EPA acceptable limit, food processing activities reduced the dietary oncogenic risk to an average 33.8%.     

A Pragmatic Approach to Assess the Exposure of the Honey Bee (Apis mellifera) When Subjected to Pesticide Spray

Plant protection spray treatments may expose non-target organisms to pesticides. In the pesticide registration procedure, the honey bee represents one of the non-target model species for which the risk posed by pesticides must be assessed on the basis of the hazard quotient (HQ). The HQ is defined as the ratio between environmental exposure and toxicity. For the honey bee, the HQ calculation is not consistent because it corresponds to the ratio between the pesticide field rate (in mass of pesticide/ha) and LD₅₀ (in mass of pesticide/bee). Thus, in contrast to all other species, the HQ can only be interpreted empirically because it corresponds to a number of bees/ha. This type of HQ calculation is due to the difficulty in transforming pesticide field rates into doses to which bees are exposed. In this study, we used a pragmatic approach to determine the apparent exposure surface area of honey bees submitted to pesticide treatments by spraying with a Potter-type tower. The doses received by the bees were quantified by very efficient chemical analyses, which enabled us to determine an apparent surface area of 1.05 cm²/bee. The apparent surface area was used to calculate the exposure levels of bees submitted to pesticide sprays and then to revisit the HQ ratios with a calculation mode similar to that used for all other living species. X-tomography was used to assess the physical surface area of a bee, which was 3.27 cm²/bee, and showed that the apparent exposure surface was not overestimated. The control experiments showed that the toxicity induced by doses calculated with the exposure surface area was similar to that induced by treatments according to the European testing procedure. This new approach to measure risk is more accurate and could become a tool to aid the decision-making process in the risk assessment of pesticides.     

Effects of pesticides commonly used in peach orchards in Brazil on predatory lacewing <Emphasis Type="Italic">Chrysoperla carnea</Emphasis> under laboratory conditions

Effects of the maximum field recommended concentration of five pesticides currently used on peaches in Brazil; abamectin, deltamethrin, methoxyfenozide, phosmet and trichlorfon were tested on the predator Chrysoperla carnea (Stephens) (Neuroptera, Chrysopidae). Dimethoate was used as positive standard. Three analytical laboratory tests, based on IOBC—working group pesticides and beneficial organisms guidelines were used: (1) exposure to fresh pesticide residue on glass plates of (a) larvae (susceptible life stage) and (b) adults (less susceptible life stage); (2) direct spraying of eggs and pupae; (3) exposure of larvae and adults to pesticide residues on plant leaves at different intervals after application (persistence). In tests 1, abamectin was slightly harmful to C. carnea larvae and phosmet and trichlorfon were slightly harmful and moderately harmful to C. carnea adults, respectively. After direct spraying of eggs and pupae, all the pesticides were harmless. In the persistence tests, abamectin and trichlorfon were classified as short lived and therefore they could be considered for use in Integrated Pest Management (IPM) programs under special conditions (i.e. reduced direct contact). Phosmet, however, caused between 56.3 and 75.0% mortality up to 30 days after treatment and it was rated as persistent. No sublethal effects were detected in the reproductive behaviour of adults (fecundity and fertility) compared with the control in any treatment. In conclusion, the insecticides with little or no toxicity to C. carnea such as abamectin, deltamethrin and methoxyfenozide could be considered as IPM-compatible, subject to further field studies.     

Estimating susceptibility of biological control agents to pesticides: influence of life history strategies and population structure

In this study we examined the influences that differing life history strategies and population structures at the time of pesticide exposure have on population susceptibility to pesticides. We used life table data and a matrix projection model to incorporate combinations of mortality (lethal effect) and reductions in fecundity (sublethal effect) into estimates of intrinsic population growth rates (r) for a predator, the seven-spot lady beetle, Coccinella septempunctata L., and its prey, the pea aphid, Acyrthosiphon pisum Harris, and an aphid parasitoid, Diaeretiella rapae (M’Intosh). All three species exhibited differences in key life history variables. The aphid had the highest r and shortest generation time, the ladybeetle had the lowest r and longest generation, while the parasitoid exhibited intermediate life history characteristics. When the model was run with populations started as neonates (aphids) or eggs (lady beetle, parasitoid) for each species, ladybeetle populations were much more susceptible than either aphid or parasitoid populations 30 days after simulated exposure to a pesticide. For example, 50% mortality and a 50% reduction in fecundity resulted in a population headed toward extinction (negative r) for the ladybeetle while the parasitoid population grew exponentially (positive r) even after sustaining 70% mortality and a 70% reduction in fecundity. The aphid species maintained exponential growth after sustaining 80% mortality and an 80% reduction in fecundity. Thus, differences in life history variables accounted for the greater susceptibility of the ladybeetle to a pesticide than its aphid prey or the parasitoid over a set time interval. These differences in susceptibility were greatly reduced when the model was run starting with a mixed age/stage population (the stable age distribution) for each species indicating that population structure at the time of pesticide exposure plays a critical role in population susceptibility. These results suggest that life history attributes as well as population structure at the time of pesticide exposure both play a major role in population susceptibility to pesticides, highlighting the need to explicitly consider differences in life history variables among species when calculating compatibility of pesticides and biological control agents as well as the population structure of beneficial species at the time of pesticide application.     

朱砂叶螨对不同农药抗药性发展趋势的研究

探讨朱砂叶螨室内种群的抗药性发展状况。实验结果表明,氧化乐果、三氯杀螨醇、双甲脒、哒螨灵对于朱砂叶螨种群,只要给予一定的选择压力,经数次用药该螨就会发展对这些杀虫(螨)剂的抗性,且随着用药次数的增加,各品系抗药性呈现上升趋势。在相同条件下,该螨对上述药剂的抗性发展速率不同,4种杀虫(螨)剂抗性发展速率由大到小依次为:氧化乐果、双甲脒、三氯杀螨醇、哒螨灵。     

Pesticide Residues and Bees – A Risk Assessment

Bees are essential pollinators of many plants in natural ecosystems and agricultural crops alike. In recent years the decline and disappearance of bee species in the wild and the collapse of honey bee colonies have concerned ecologists and apiculturalists, who search for causes and solutions to this problem. Whilst biological factors such as viral diseases, mite and parasite infections are undoubtedly involved, it is also evident that pesticides applied to agricultural crops have a negative impact on bees. Most risk assessments have focused on direct acute exposure of bees to agrochemicals from spray drift. However, the large number of pesticide residues found in pollen and honey demand a thorough evaluation of all residual compounds so as to identify those of highest risk to bees. Using data from recent residue surveys and toxicity of pesticides to honey and bumble bees, a comprehensive evaluation of risks under current exposure conditions is presented here. Standard risk assessments are complemented with new approaches that take into account time-cumulative effects over time, especially with dietary exposures. Whilst overall risks appear to be low, our analysis indicates that residues of pyrethroid and neonicotinoid insecticides pose the highest risk by contact exposure of bees with contaminated pollen. However, the synergism of ergosterol inhibiting fungicides with those two classes of insecticides results in much higher risks in spite of the low prevalence of their combined residues. Risks by ingestion of contaminated pollen and honey are of some concern for systemic insecticides, particularly imidacloprid and thiamethoxam, chlorpyrifos and the mixtures of cyhalothrin and ergosterol inhibiting fungicides. More attention should be paid to specific residue mixtures that may result in synergistic toxicity to bees.     

Occurrence and risk assessment of organophosphorus pesticide residues in Chinese tea

Tea is the second widely consumed beverage next to water. Tea drinking is one of the important pathways for human exposure of organonphosphorus pesticide. Consequently, incidence of organonphosphorus pesticide residues and risk assessment should be clear. In this study, the level of organonphosphorus pesticide residues in 810 Chinese teas manufactured between 2010–2013 was investigated using gas chromatography coupled with tandem mass spectrometry and a flame photometric detector. Incidence of organonphosphorus pesticide residues occurred with a frequency of 29% and the average concentration of 93 μg kg^?1. The residue levels varied from tea types, sale spots, and production area. Chlorpyrifos, isocarbophos, and triazophos were the only three organonphosphorus pesticides with detectable residues, and the detectable rates were 13.0%, 13.6%, and 17.4%, respectively. The corresponding average daily intake of chlorpyrifos, isocarbophos, and triazophos by tea drinking was 0.000083 μg kg^?1 bw day^?1, 0.0036 μg kg^?1 bw day^?1, and 0.0022 μg kg^?1 bw day^?1. These results showed that the total hazard quotient of organonphosphorus pesticide pesticides from tea drinking was less than 0.02 and that the tea-drinking originated organonphosphorus pesticide exposure had a little adverse health effect for human being.     

Evaluation of selected plant growth regulators and fungicide residues in fruits for dietary risk assessment

A total of 96 samples of fresh fruits were collected to investigate the residues of selected plant growth regulators and fungicides. The analyses utilized ultra-high-performance liquid chromatography coupled with tandem mass spectrometry after a modified QuEChERS method. The results were evaluated according to maximum residue limits (MRLs) by the Chinese regulation. All blueberries, litchis, and watermelons were pesticide-free, and only one (1%) fruit sample contained pesticide residues above MRLs. Concerning the most frequently detected pesticide residues, carbendazim was found in 20% of the samples analyzed. Data obtained were then used to estimate the potential health risks associated with the exposures to these pesticides. The short-term risks were below 3.25% and the long-term risks were also very low, ranging from 0.0005% for dimethomorph to 0.4302% for prochloraz.     

Dietary Intake of Pesticides Based on Vegetable Consumption in Ismailia,Egypt: A Case Study

The objective of this study was to assess pesticide residues in tomatoes, cucumbers, peppers, strawberries, and potatoes collected from local markets in Ismailia, Egypt, and to assess dietary intake and health risk implications of pesticide residues through food consumption. Vegetable selection was based on their popularity and consumption. Selection of pesticides was based on their impact on humans, and on their heavy use. The majority of the analyzed samples contained detectable levels of pesticides. Residues of some organophosphorus pesticides, including malathion, ethion, and profenofos and some pyrethroid pesticides such as fenpropathrin and cypermethrin were found in some samples at concentration equal to or exceeding their European Union's maximum residue limits (EU-MRLs). The fungicide bupirimate detected in potato samples exceeded the EU-MRL by 1500%. Phentohate and profenofos were the most frequently detected pesticides in 30 and 27% of analyzed samples, respectively. Data were used to estimate the potential health risks associated with exposure to these pesticides by ingestion of food. Estimated daily intakes (EDIs) of pesticides ranged from 0.03% to 40% of the acceptable daily intakes (ADIs), depending on pesticide concentration and vegetable consumption. Overall, the EDIs of the different pesticides from vegetable consumption are not considered a public health problem.