Dissipation rates of fenitrothion in greenhouse grown lettuce and under cold storage conditions

The dissipation of fenitrothion ( O , O -dimethyl O - p -nitro- m -tolyl phosphothioate) was evaluated by gas chromatography (GC) with nitrogen-phosphorus detection (NPD) in lettuce samples grown in an experimental greenhouse and harvested over a 4 weeks period following treatment with this insecticide. Dissipation followed a pseudo-first-order kinetics ( r was 0.996). The recommended preharvest time (PT) of application is 15 days, and when the residual value of fenitrothion was evaluated at harvest, it was found to be above the maximum residue limit (MRL) established by Spanish law in the field experiment for this compound. During the experiment, the evolution of the two main fenitrothion metabolites (3-methyl-4-nitrophenol and fenitrothion-oxon) was also evaluated. When the dissipation of fenitrothion was evaluated in cold-stored lettuce the half-life was 9–10 times greater than in greenhouse conditions.     

Dissipation rates of insecticides and fungicides in peppers grown in greenhouse and under cold storage conditions

The dissipation of three insecticides (pirimicarb, pyriproxyfen and buprofezin) and three fungicides (cyprodinil, fludioxonil and tebuconazole) in peppers was evaluated in a study carried out on an experimental greenhouse. Pepper samples were collected during 6 week period in which two successive applications of these pesticides were performed. Gas chromatography (GC) with nitrogen–phosphorus detection (NPD) was used to study the disappearance of these compounds in peppers. Confirmation analysis of pesticides was carried out by capillary gas chromatography coupled with mass spectrometry in the selected ion monitoring (SIM) mode. At the preharvest interval the residue levels were below the legal limit established in Spain. The disappearance rates of these compounds on peppers were described as pseudo-first-order kinetics (r between 0.953 and 0.997) and half-life in the range of 4.41 and 21.47 days. After thirty days under cold and darkness storage conditions, dissipation of buprofezin and pyriproxyfen were not observed. However, dissipation rate in pepper of pirimicarb cyprodinil, fludioxonil and tebuconazole in refrigerated were observed. This, the half-lives for these pesticides were 5–9 times greater under refrigeration.     

培养条件对副溶血性弧菌AI-2活性及其合成关键基因表达水平的影响

目的以海产品中分离的一株高产信号分子AI-2(Autoinducer-2)的副溶血性弧菌Vp2009027为研究对象,分析不同的培养条件(时间、温度、糖源、pH和盐度)对菌株AI-2活性及其合成关键基因表达水平的影响。方法采用报告菌株检测AI-2的活性变化,采用逆转录-实时荧光定量PCR法检测合成关键基因luxS和pfs表达量的变化。结果菌株培养12 h后AI-2活性达到最高,当培养温度为30℃时AI-2活性最高,添加糖源、中性和偏碱性环境以及适度的盐度均可促进AI-2活性的提高;不同培养条件下AI-2合成关键基因luxS和pfs的表达量均有不同程度的变化,温度和糖源对AI-2活性的影响与对luxS和pfs基因表达量的影响呈正相关,其他条件下AI-2的活性与luxS和pfs的表达量没有明显相关性。结论不同培养条件可以调控AI-2的合成,可以通过改变培养条件来获得不同产量的AI-2。     

Effects of varying concentrations of sodium chloride and acidic conditions on the behavior of Vibrio parahaemolyticus and Vibrio vulnificus cold-starved in artificial sea water microcosms

Food Science and Biotechnology - There has been limited information available on the behavior of Vibrio parahaemolyticus and Vibrio vulnificus as a function of higher levels of NaCl in combination...     

Effectiveness of icing as a postharvest treatment for control of Vibrio vulnificus and Vibrio parahaemolyticus in the eastern oyster (Crassostrea virginica)

The focus of this research was to investigate the efficacy of icing as a postharvest treatment for reduction of the levels of Vibrio vulnificus and Vibrio parahaemolyticus in commercial quantities of shellstock oysters. The experiments were conducted in June and August of 2006 and consisted of the following treatments: (i) on-board icing immediately after harvest; (ii) dockside icing approximately 1 to 2 h prior to shipment; and (iii) no icing (control). Changes in the levels of pathogenic Vibrio spp. during wholesale and retail handling for 2 weeks postharvest were also monitored. On-board icing achieved temperature reductions in all sacks in accordance with the National Shellfish Sanitation Program standard, but dockside icing did not meet this standard. Based on one-way analysis of variance, the only statistically significant relationship between Vibrio levels and treatment occurred for samples harvested in August; in this case, the levels of V. vulnificus in the noniced oysters were significantly higher (P < 0.05) than were the levels in the samples iced on-board. When analyzing counts over the 14-day storage period, using factorial analysis, there were statistically significant differences in V. vulnificus and V. parahaemolyticus levels by sample date and/or treatment (P < 0.05), but these relationships were not consistent. Treated (iced) oysters had significantly higher gaping (approximately 20%) after 1 week in cold storage than did noniced oysters (approximately 10%) and gaping increased significantly by day 14 of commercial storage. On-board and dockside icing did not predictably reduce the levels of V. vulnificus or V. parahaemolyticus in oysters, and icing negatively impacted oyster survival during subsequent cold storage.     

Production and rapid extraction of lutein and the other lipid-soluble pigments from Chlorella protothecoides grown under heterotrophic and mixotrophic conditions

Chlorella protothecoideswas successfully cultivated under mixotrophic and heterotrophic conditions. The maximum biomass concentrations of the alga grown at an initial glucose concentration of 40 g/l in the light and in the dark were 22.4 g/l and 17.2 g/l dry cells, respectively. A mechanical method using a new model of dispersing instrument, Ulta-Turrax T25, was developed for the extraction of the pigments from C. protothecoidescells. Lutein and the other lipid-soluble pigments were separated well by an HPLC system. The contents of lutein, α-carotene, β-carotene, chlorophyll a and chlorophyll b extracted by the mechanical method from the heterotrophic and mixotrophic C. protothecoidescells were 4.43, 0.32, 0.94, 43.76, 9.14 and 6.48, 0.55, 0.66, 56.75, 9.78 mg/g dry cells, respectively. The recoveries of the five pigments through the mechanical extraction were 97.5–99.6%. In contrast, no chlorophylls a and b were obtained through the alkali extraction.     

Occurrence of Vibrio vulnificus in fish and shellfish available from markets in China

Vibrio vulnificus is a naturally occurring estuarine bacterium often associated with disease such as septicemia in humans following consumption of raw and lightly cooked seafood. In China and neighboring countries, rapid economic growth has encouraged increased consumption of seafood, and dietary habits are changing, with more people eating raw fish. In this study, the prevalence of V. vulnificus was investigated in 48 samples from 11 species of live seafood available from markets in coastal cities of China. The bacterium was detected in four of four razor clam samples, in seven of seven giant tiger prawn samples, and in five of nine mantis shrimp samples. The bacterium was also found in water samples of the prawn aquaria at the markets. The maximum level of V. vulnificus was 3.4 log CFU/g in the razor clam samples and 4.9 log CFU/g in the prawn samples by a direct spreading method. Differential bacterial counts on the prawn body revealed that most of the bacteria were found on the shells (exoskeletons), with very few in the edible muscle. However, dense populations can be found in the intestines. Biochemical tests indicated that the isolates of V. vulnificus were biotype 1 strain, which is pathogenic to humans. These isolates were susceptible to ampicillin, penicillin, kanamycin, streptomycin, and erythromycin. These results suggest that V. vulnificus is a potential health hazard to humans in cities consuming and handling live shellfish, especially giant tiger prawns.     

Sterol glycosides and cerebrosides accumulate in Pichia pastoris, Rhynchosporium secalis and other fungi under normal conditions or under heat shock and ethanol stress

The occurrence of glycolipids such as sterol glycosides, acylated sterol glycosides, cerebrosides and glycosyldiacylglycerols was examined in the three yeast species Candida albicans, Pichia pastoris and Pichia anomala, as well as in the six fungal species Sordaria macrospora, Pyrenophora teres, Ustilago maydis, Acremonium chrysogenum, Penicillium olsonii and Rhynchosporium secalis. Cerebroside was found in all organisms tested, whereas acylated sterol glycosides and glycosyldiacylglycerols were not found in any organism. Sterol glycosides were detected in P. pastoris strain GS115, U. maydis, S. macrospora and R. secalis. This glycolipid occurred in both yeast and filamentous forms of U. maydis but in neither form of C. albicans. This suggests that sterol glycoside is not correlated with the separately grown dimorphic forms of these organisms. Cerebrosides and sterol glycosides from P. pastoris and R. secalis were purified and characterized by mass spectrometry and nuclear magnetic resonance spectroscopy. The cerebrosides are beta-glucosyl ceramides consisting of a saturated alpha-hydroxy or non-hydroxy fatty acid and a Delta4,8-diunsaturated, C9-methyl-branched sphingobase. Sterol glycoside from P. pastoris was identified as ergosterol-beta-D-glucopyranoside, whereas the sterol glucosides from R. secalis contain two derivatives of ergosterol. The biosynthesis of sterol glucoside in P. pastoris CBS7435 and GS115 depended on the culture conditions. The amount of sterol glucoside in cells grown in complete medium was much lower than in cells from minimal medium and a strong increase in the content of sterol glucoside was observed when cells were subjected to stress conditions such as heat shock or increased ethanol concentrations. From these data we suggest that, in addition to Saccharomyces cerevisiae, new yeast and fungal model organisms should be used to study the physiological functions of glycolipids in eukaryotic cells. This suggestion is based on the ubiquitous and frequent occurrence of cerebrosides and sterol glycosides, both of which are rarely detected in S. cerevisiae. We suggest P. pastoris and two plant pathogenic fungi to be selected for this approach.     

Growth kinetics of Vibrio parahaemolyticus O3:K6 under varying conditions of pH, NaCl concentration and temperature

The growth responses of Vibrio parahamolyticus to pH, NaCl concentration and temperature changes were studied using serotype O3:K6 and other strains. Growth curves were obtained for 27 different sets of conditions, comprised of three levels of NaCl concentration, pH and temperature. The temperature, pH and NaCl concentrations most favorable for growth were in the order of 25 degrees C, 20 degrees C and 15 degrees C, pH 8, 7 and 5.8, and 1%, 3% and 7%, respectively. The bacteria grew most rapidly at 25 degrees C, at a pH of 7 or 8 in the presence of 1% or 3% NaCl, with the population (initial, ca. 2.5 log CFU/mL) reaching a level log 7 CFU/mL at 12 h. A growth predictive model using the Gompertz equation was generated from the experimental data for any combination of NaCl concentration, pH and temperature within the range used in this study.     

冷应激及包埋对乳酸菌冻干发酵剂的影响

将嗜热链球菌、保加利亚乳杆菌、嗜酸乳杆菌按3∶2∶1比例制备乳酸菌冻干发酵剂.比较不同温度冷应激处理对乳酸菌冻干存活率的影响,结果表明,20℃,处理4h时,冻干存活率为96.3％.选择发酵的固定化细胞制作条件:海藻酸钠2.25g/L、CaCl2 4.0g/L.包埋后乳酸菌冻干存活率为95.6％.     

Expression of major cold shock proteins and genes by Yersinia enterocolitica in synthetic medium and foods

Yersinia enterocolitica is a psychrotrophic foodborne pathogen that has been implicated in outbreaks of foodborne illness involving cold-stored foods, especially milk and pork. A major mechanism bacteria use to adapt to cold is expression of cold shock proteins. The objective of this research was to study the expression of major cold shock proteins of Y. enterocolitica in Luria-Bertani (LB) broth, milk, and pork following a temperature downshift from 30 to 4 degrees C. Y. enterocolitica was inoculated into 10 ml of LB broth, sterile skim milk, or pork, and the samples were stored at 4 degrees C (cold shock) or 30 degrees C (control) for 0, 4, 8, 12, and 24 h. At each sampling time, total protein and total RNA were extracted from Y. enterocolitica harvested from LB broth, milk, and pork and subjected to two-dimensional gel electrophoresis and dot blot analysis. Two major cold shock proteins (CspA1 and CspA2) of approximately 7 kDa and their genes were expressed by Y. enterocolitica following cold shock. However, the CspA1 and CspA2 proteins were not expressed by Y. enterocolitica at 30 degrees C. Y. enterocolitica CspA1 and CspA2 were observed as early as 2 h of cold shock in cultures from LB broth and milk and at 8 h of cold shock in cultures from pork.     

Ethanol shock changes the fatty acid profile and survival behavior of Vibrio parahaemolyticus in various stress conditions

Vibrio parahaemolyticus 690, a clinical strain, was subjected to ethanol shock in the presence of 5% ethanol for a period of 30 and 60 min. Survival behaviors of the ethanol shocked and control cells of V. parahaemolyticus in the presence of H(2)O(2) (20 ppm), crystal violet (3 ppm), NaCl (20%), and low pH solution (pH 4.4) containing various organic acids including lactic acid, acetic acid, citric acid and tartaric acid (25 mM) were compared. In addition, the effects of ethanol shock on the fatty acid profile and recovery of V. parahaemolyticus on tryptic soy agar (TSA) plus various amounts of NaCl were also investigated. After ethanol shock, it was found that the proportion of vaccenic acid (18:1) increased, while the proportion of palmitic acid (16:0) and ratio of saturated fatty acid to unsaturated fatty acid decreased in cells of V. parahaemolyticus. The recovery of the ethanol-shocked cells on TSA plus 6.0% or 7.5% NaCl was significantly less than the control cells. Furthermore, ethanol shock increased the survival of V. parahaemolyticus in the presence of H(2)O(2), while made the test organism less resistant to crystal violet, high NaCl and organic acids. The degree of decreased acid tolerance observed on the ethanol-shocked cells of test organism varied with the organic acid examined. Finally, ethanol shock for 60 min exhibited either a higher or similar degree of effect on the test organism (depending on the type of stress encountered) than did ethanol shock for 30 min. Data obtained from the present study does provide useful information that is indispensable when control measure of V. parahaemolyticus is to be performed efficiently and adequately.     

Stable maintenance of plasmid in continuous culture of yeast under non-selective conditions

A recombinant yeast plasmid containing the gene for beta-galactosidase was tested for stability in a host auxotrophic for leucine. Plasmid loss was studied at different dilution rates in continuous culture under selective as well as non-selective conditions. It was observed that the instability of the culture was higher at low dilution rates in selective medium, while the pattern was reversed when complex non-selective medium was used, with plasmid-containing cells competing effectively with plasmid-free cells at low dilution rates. This was attributed to a low residual yeast extract concentration in the medium at low dilution rates. Since yeast extract was the sole source of leucine, this limited the growth of plasmid-free cells, which were auxotrophic for leucine. Growth rate studies also indicated a competitive advantage of the plasmid-containing cells over the plasmid-free cells at low yeast extract concentrations in semi-defined medium. Using the above data, a modified continuous culture was run using non-selective medium at a low dilution rate of 0.05 h(-1). This resulted in stable coexistence of plasmid-containing and plasmid-free cells and hence sustained expression of beta-galactosidase at approximately 330 OD420l(-1) h(-1) throughout the period of cultivation (134 h).     

Transpiration efficiency and carbon-isotope discrimination of grapevines grown under well-watered conditions in either glasshouse or vineyard

This paper describes variation in transpiration efficiency ‘W’ (where W = dry matter produced/water transpired) among grapevine genotypes grown under well‐watered conditions in either a glasshouse or a vineyard. Nineteen genotypes were grown in a glasshouse where growth and transpiration were measured. W ranged from 2.5 to 3.4 g dm/kg H₂O transpired. Carbon‐isotope discrimination (Δ) of laminae dry matter ranged from 20.8 to 22.7%o and there was a negative relationship (R²= 0.58) between W and Δ. A large proportion of variation in W could be attributed to variation in stomatal conductance. Genotypic variation in photosynthetic capacity was also an important component of variation in W. In a second experiment, lamina Δ was measured for mature field‐grown Shiraz and Chardonnay, grown either on their own roots or grafted to five different rootstocks, and maintained at three sites under well‐watered conditions. At all sites and regardless of rootstock, the laminae of Chardonnay had Δ values 1 to 2%o lower than Shiraz. There was also a 1 to 2%o variation among the sites. Rootstock variety affected Δ values inconsistently and by a maximum of 0.5%o. Leaf gas exchange measurements were performed at a single site on sun‐exposed leaves of Chardonnay and Shiraz on either their own roots or 1103 Paulsen, a moderate to high vigour rootstock. There was no significant effect of rootstock on leaf gas exchange and photosynthetic rates did not differ between scion varieties. However, Chardonnay had a 20% lower stomatal conductance and a 1.4‐fold higher ratio of CO₂assimilation/H₂O transpiration (A/T) indicating a potentially higher W, at a leaf level, for Chardonnay compared with Shiraz. We conclude that photosynthetic capacity was also higher for Chardonnay. Δ values, predicted from the C_i/C_a ratio calculated from leaf gas exchange measurements, did not differ significantly from measured values for laminae Δ. This similarity for Δ, in conjunction with the fact that the lower Δ of Chardonnay was reflected in a higher A/T ratio, suggests that Δ may be a reliable predictor of comparative W under vineyard conditions.     

Total and individual glucosinolate contents in inflorescences of eight broccoli cultivars grown under various climatic and fertilisation conditions

Total aliphatic, indolic and aromatic glucosinolates were evaluated in the edible portions of fresh harvested inflorescences of five commercial and three experimental broccoli (Brassica oleracea L var italica) cultivars grown under various climatic and agronomic conditions, ie early (winter) or late (spring) season with poor (15 kg ha^?1) or rich (150 kg ha^?1) sulphur fertilisation, in an attempt to identify differences due to genetic and agronomic factors. The predominant glucosinolates in all broccoli cultivars were 4‐methylsulphinylbutyl‐glucosinolate (glucoraphanin), 3‐indolylmethyl‐glucosinolate (glucobrassicin) and 1‐methoxy‐3‐indolylmethyl‐glucosinolate (neoglucobrassicin). The results showed no significance differences in total glucosinolates between rich and poor fertilisation, whereas total glucosinolates were detected more significantly in the late than in the early season. All broccoli cultivars showed a higher content of indolic glucosinolates than aliphatic glucosinolates. Clear advantages were detected in the analysed commercial cultivars, as the experimental cultivars yielded lower concentrations of these compounds. © 2003 Society of Chemical Industry     

野生粉叶爬山虎种子等部位的原花青素提取纯化工艺及含量测定

通过正交实验研究粉叶爬山虎中原花青素提取条件。结果表明:提取时间100min,乙醇体积分数75%,提取温度65℃,料液比1:10为较佳条件。香草醛-盐酸法测得果梗、果皮、种子中含量分别为2.6317%、3.7967%、4.0934%;大孔吸附树脂分离纯化的结果表明:LSA-21树脂适合分离纯化粉叶爬山虎中原花青素,分离条件:上样液质量浓度为20mg/mL,洗脱流速为2.0BV/h,经HPLC测得纯化后果梗、果皮与种子中原花青素含量为2.39%、2.31%、3.94%;HPLC检测LSA-21树脂分离纯化后的原花青素纯度可达87%以上。     

常温与冷藏条件下不同阶段鸡肉呈味核苷酸及游离氨基酸含量的变化

研究鸡肉在常温与冷藏条件下呈味核苷酸及游离氨基酸含量的变化。结果表明:常温条件下,6 h时鸡胸肉和鸡腿肉肌苷酸(IMP)含量达到最高,分别为2.27、1.97 mg/g,然后开始显著下降(p<0.05);宰后随贮藏期延长,测定的17种游离氨基酸含量均有不同程度增加,鸡胸肉和鸡腿肉风味氨基酸占比分别在6 h和12 h时达到最大值,依次为59.3%、61.8%。冷藏条件下,IMP含量随时间延长呈先升后降的规律,鸡胸肉和鸡腿肉分别在48 h和36 h时IMP含量达到最大值,即3.14 mg/g和2.81 mg/g,而后缓慢降低;鸡胸肉和鸡腿肉风味氨基酸占比峰值均出现在宰后低温下48 h时,分别为67.1%、66.4%。因此,低温贮藏可以抑制鸡肉中IMP在贮藏过程中的降解,相对于常温贮藏,冷藏可以促进鸡肉中游离氨基酸的生成,有利于提高鸡肉的食用风味。