霍氏肠杆菌A20降解类胡萝卜素的条件优化

为了提高类胡萝卜素的降解率,以霍氏肠杆菌（Enterobacter hormaechei）A20菌株为对象,研究其培养条件(培养时间、培养温度、转速、pH值、接种量)对类胡萝卜素降解率的影响,并通过单因素和正交试验,以降解率为评价指标,确定微生物的最佳培养条件。结果表明,培养条件的改变可以影响类胡萝卜素的降解效果,各培养条件对类胡萝卜素的降解率的影响程度不同。菌株A20降解类胡萝卜素的最佳培养条件为培养时间42 h,温度25 ℃,转速150 r/min,pH值7.0,接种量1.0%,在此条件下,类胡萝卜素降解率从最初的70.80%提高至91.53%。     

海藻酸钠-明胶协同固定化交联漆酶及在鼓泡式反应器中降解双酚A

为了提高漆酶的稳定性,该研究预先将酶与戊二醛反应形成交联漆酶,然后再以海藻酸钠和明胶为载体对交联漆酶进行包埋固定化,考察了影响固定化交联漆酶制备的主要因素。结果显示,当戊二醛的质量分数为2.0%、m(海藻酸钠)∶m(明胶)=1∶1、CaCl₂ 15 g/L时的固定化效果最好,所制备的固定化交联漆酶的稳定性比固定化游离酶有了较大的提高。在鼓泡式反应器中对双酚A的降解试验表明,连续5个批次的反应以后固定化交联酶剩余酶活力为34.93%,双酚A的降解率仍能达到71.13%,分别是固定化游离酶的7.97倍和4.43倍。该研究提供了一种固定化漆酶的新方法,适合重复性和连续性的操作,具有一定的应用潜力。     

固相萃取-超高效液相色谱-串联质谱法测定饮用水中双酚A和双酚S

建立一种饮用水中痕量双酚A和双酚S的固相萃取-超高效液相色谱-串联质谱检测方法。水样中双酚A和双酚S经HLB固相萃取柱富集,甲醇洗脱并浓缩,再以1 mmol/L氟化铵-乙腈为流动相,经C18色谱柱分离,采用电喷雾离子源、质谱多反应监测模式分析。该方法对水样体积为500 mL时双酚A和双酚S检出限分别可达到1.0 ng/L和0.2 ng/L,在低、中、高3 个加标水平下两者的平均回收率分别为88.3%～114.8%和83.7%～98.2%,相对标准偏差分别为10.0%～16.2%和5.9%～12.3%。该方法灵敏度高、定性准确、操作简单高效,适用于饮用水中双酚A和双酚S的定性定量分析。     

双酚A环氧衍生物在罐头食品中的迁移规律与污染情况研究

罐头内壁涂层双酚A环氧衍生物在食品中的迁移存在安全隐患。本文模拟食品的贮存条件,研究了双酚A环氧衍生物在罐头食品中的迁移规律。实验结果表明,双酚A环氧衍生物在食品中的迁移主要受pH、温度、贮存时间的影响。在酸性条件下双酚A环氧衍生物的迁移量随浸泡时间的增长而增加,在高温下(40℃)迁移总量迅速增加。对34个罐头食品内容物进行检测,共8个样品检出双酚A环氧衍生物,检出率为23.5%。其中饮料罐头的检出率达85.7%,在酸性的饮料罐头中双酚A环氧衍生物的含量随贮存时间的增长而增加。     

食品包装材料中双酚A快速检测方法

建立食品包装材料中可迁移双酚A的气相色谱-质谱联用技术(GC-MS)检测方法。比较了甲醇水浴振荡提取法、超声提取法和索氏提取法,结果表明索氏提取法效果明显,考察索氏提取时间对提取效果的影响。在试验选定的最佳条件下,用于食品包装材料中可迁移双酚A的检测,样品加标回收率为90.1%～97.2%,方法检出限为0.50μg/kg,相对标准偏差小于3.7%。     

高效液相色谱荧光法测定食品包装材料中双酚A及双酚S的迁移量

采用高效液相色谱-荧光法检测食品包装材料中双酚A及双酚S的迁移量,研究不同的模拟液对食品包装材料中双酚A和双酚S迁移的影响以及不同浓度的乙醇溶液对双酚A和双酚S迁移特性的影响。结果表明:该方法在0.001~0.100μg/L范围内线性关系良好,在乙醇模拟液中,双酚A和双酚S的迁移效果好,乙醇浓度越高迁移率越高,相同浓度的乙醇溶液中,接触温度越高,接触时间越长迁移率越高。     

双酚A在食品模拟物中的迁移规律研究

采用高效液相色谱法,对食品接触材料中双酚A在蒸馏水、质量浓度3%乙酸、体积分数为10%乙醇和异辛烷等4种食品模拟物中的迁移规律进行了研究,研究双酚A迁移量与试验的温度、时间、pH和模拟物属性等参数的关系。结果表明:模拟物的属性对双酚A的溶出迁移行为有显著影响,双酚A的溶出迁移量随温度的升高和时间的增加而变大。     

双酚A的酶联免疫检测方法的建立

将双酚A(BPA)半抗原与牛血清白蛋白(BSA)共价偶联后,制备兔抗双酚A多克隆抗体,建立了双酚A间接竞争酶联免疫(icELISA)检测方法,并对其进行了方法学评价。结果表明:最佳的抗体稀释度为1∶1600,双酚A竞争标准曲线在0.3～100μg·mL-1之间具有良好的线性关系,最低检测浓度为0.001μg·mL-1,重现性实验变异系数均小于10%。交叉反应实验中,与双酚酸和双酚B的交叉反应率分别为20.0%和10.0%;与双酚E和4-枯基苯酚的交叉反应率均在5%以下。水样的添加回收实验,回收率范围为92.5%～107.7%。     

高效液相色谱法测定牛奶中双酚A

建立了测定牛奶中双酚A含量的高效液相色谱方法。样品经乙腈提取,C18固相萃取柱净化,然后采用高效液相色谱测定。双酚A在3.5×10-3～10mg/kg范围内呈良好线性,线性相关系数R2=0.9991。双酚A检测限为2.1×10-3mg/kg,平均添加回收率80.07%～85.53%,相对标准偏差4.42%～9.14%。采用本文所建立的方法对市售牛奶样品进行了测定,未检出双酚A残留。     

液质联用法测定皮革中卤代双酚类化合物

本文建立了采用液相色谱-串联质谱法检测皮革中四氯双酚A和四溴双酚A的方法。方法采用超声波提取器进行提取,优化了前处理方法,确立了定量方式,采用液质联用法的多反应监测模式进行分析。实验结果表明,方法的平均回收率83.0%～91.1%,相对标准偏差3.7%～6.3%,四氯双酚A和四溴双酚A这2种化合物的定量限为0.1 mg/kg和0.5 mg/kg。该方法的准确度和重现性均能达到化学分析要求,适用于皮革中四氯双酚A和四溴双酚A的检测分析。     

Photocatalytic decomposition of bisphenol A in water using composite TiO2-zeolite sheets prepared by a papermaking technique

Titanium dioxide (TiO2) photocatalyst and zeolite adsorbent were made into a paper-like composite by a papermaking technique using pulp and ceramic fibers as sheet matrix. The photocatalytic performance for the degradation of bisphenol A (BPA) dissolved in water was investigated under UV irradiation. The TiO2 sheet prepared was easier to handle than the original TiO2 powders in aqueous media. The TiO2 sheet could decompose the BPA under UV irradiation, although at a lower degradation efficiency than the TiO2 suspension. The TiO2-free zeolite sheet could not remove the BPA from water completely because of its adsorption equilibrium. Furthermore, the composite TiO2-zeolite sheets exhibited a higher efficiency for BPA removal than the zeolite-free TiO2 sheets, the efficiency of the former being equivalent to that of the TiO2 suspension. The enhancement in removal efficiency was not attributed to the simple adsorption of BPA on zeolite but rather to the synergistic effect obtained through the combined use of TiO2 photocatalyst and zeolite adsorbent in the paper-like composite sheet, which is believed to accelerate the BPA photodegradation in water.     

Oxidative degradation of alkylphenols by horseradish peroxidase

Alkylphenols such as bisphenol A (2,2-bis(4-hydroxyphenyl)propane; BPA), p-nonylphenol (p-NP), and p-octylphenol (p-OP) that are known as endocrine disrupters were oxidized by horseradish (Armoracia rusticana) peroxidase (HRP) with H2O2. The optimal pHs for BPA, p-NP, and p-OP were 8.0, 7.0, and 5.0, respectively. The optimal temperature for BPA was 20 degrees C. Although BPA was rapidly degraded by HRP, its degradation depended on the concentration of HRP. Most of the oxidation products of BPA were polymers, although some 4-isopropenylphenol was produced. When male Japanese medaka (Oryzias latipes) were exposed to BPA, vitellogenin in the blood increased. However, no increased vitellogenin was observed in medaka exposed to HRP-oxidized BPA. The enzymatic oxidation of BPA using HRP was able to eliminate its estrogen-like activity.     

Stability of Bisphenol A (BPA) in Oil-In Water Emulsions under Riboflavin Photosensitization

Effects of riboflavin photosensitization on the degradation of bisphenol A (BPA) were determined in oil-in-water (O/W) emulsions containing ethylenediaminetetraacetic acid (EDTA) or sodium azide, which are a metal chelator or a singlet oxygen quencher, respectively. Also, the distribution of BPA between the continuous and dispersed phases in O/W emulsions was analyzed by high-performance liquid chromatography (HPLC). The concentration of BPA in O/W emulsions significantly decreased by 38.6% after 2 h under visible light irradiation and in the presence of riboflavin (P < 0.05). Addition of EDTA and sodium azide protected the decomposition of BPA significantly in a concentration dependent manner (P < 0.05), which implies both transition metals and singlet oxygen accelerate the photodegradation of BPA in O/W emulsions. Approximately 21.7% of the BPA was distributed in the 2.5% (w/v) dispersed lipid particles and 78.3% was in the continuous aqueous phase of the emulsions. The amount of BPA in aqueous phase decreased faster than the amount of BPA in the lipid phase during riboflavin photosensitization (P < 0.05). Thus, the BPA in the aqueous phase was the major target of riboflavin photodegradation in O/W emulsions. Practical Application: Concentration of BPA, an endocrine disrupting chemical, was decreased significantly in oil-in-water emulsions under riboflavin and visible light irradiation. BPA in continuous aqueous phase was major target of riboflavin photosensitization. However, BPA was distributed more densely in lipid phase and more protected from riboflavin photosensitized O/W emulsions. This study can help to decrease the level of BPA in foods made of O/W emulsions containing riboflavin, which could be displayed under visible light irradiation.     

Efficient microbial degradation of bisphenol A in the presence of activated carbon

The biodegradation of bisphenol A (BPA) was carried out with Sphingomonas sp. strain BP-7 and Sphingomonas yanoikuyae BP-11R in the presence of activated carbon (AC). When AC was present, both BPA-degrading bacteria efficiently degraded 300 mg/l BPA without releasing 4-hydroxyacetophenone, the major intermediate produced in BPA degradation, into the medium. The biological regeneration of AC was possible using the BPA-degrading bacteria, suggesting that an efficient system for BPA removal can be constructed by introducing BPA-degrading bacteria into an AC treatment system.     

Release of bisphenol A from polycarbonate baby bottles: mechanisms of formation and investigation of worst case scenarios

The question was further investigated whether there could be conditions resulting in contamination of beverages in polycarbonate bottles for babies with bisphenol A (BPA) at concentrations causing the tolerable daily intake (TDI) to be approached or exceeded. It is a follow up of previous work showing increased release of BPA after extended use of the bottles. Migration in the proper sense was low, but larger amounts of BPA were observed from degradation of the polycarbonate. Since there are no standardized testing conditions to determine release by degradation of the polymer, worst case scenarios were investigated. Alkali washing solutions at concentrations typical for dishwashers contained BPA in concentrations little above 100 μg/l. In reality they are diluted in the general washing liquid and finally poured out. Drying was the most critical step, particularly after inadequate rinsing of bottles, when alkali detergent was “baked” to the bottle wall at elevated temperature. BPA thus formed is transferred into the beverage, but is unlikely to exceed 10 μg/l. The highest transfer into the beverage (up to about 500 μg/l) could occur when the bottle is positioned in the dishwasher at such inclination that the detergent solution does not fully run off and is poorly rinsed, but this scenario is unlikely to often occur. In conclusion, even rather extreme scenarios do not result in BPA contamination near to the level corresponding to the TDI.     

Estrogenic activity of impurities in industrial grade bisphenol A

The estrogenicities of 10 compounds found as impurities in industrial grade bisphenol A (BPA) were measured by yeasttwo-hybrid assays incorporating the human estrogen receptor alpha(hERalpha) orthe medaka fish (Oryziaslatipes) estrogen receptor alpha (medERalpha). Five impurities showed greater activity than BPA itself in an agonist assay for hERalpha. p-Cumylphenol, the most active of the impurities in the hERalpha assay, was 12 times as active as BPA. The REC10 (10% relative effective concentration: 10% of the activity of 10(-8)M 17,B-estradiol) was 710 nM. Five impurities showed greater activity than BPA in an agonist assay for medERa: 4,4'-(1,3-dimethylbutylidene) bisphenol and 2-(4'-hydroxy-phenyl)-2,4,4-trimethylchroman were nearly equipotent and 9 times as active as BPA, and the REC10 values of these compounds in the medERalpha assay were 280 and 320 nM, respectively. Comparison of the experimentally determined estrogenicities of mixtures of BPA and 4,4'-(1,3-dimeth-ylbutylidene) bisphenol and those calculated by the concentrations addition (CA) method confirmed the suitability of the method for the prediction of the estrogenicities of the mixtures of BPA and its phenolic analogues. The measured estrogenicities of four samples of industrial grade BPA and laboratory grade (pure) BPA were not significantly different in either the hERalpha assay or the medERalpha assay (p > 0.05 in each case). We conclude that the impurities in industrial grade BPA, although some are of much higher estrogenic activity than BPA itself, do not significantly increase the estrogenicity of the industrial compound and therefore do not increase possible adverse health effects from such activity.     

Solid-phase extraction for selective determination of bisphenol A in drinks and fruits by dummy surface molecularly imprinted polymer with direct synthetic method

A reliable and selective method was developed for the determination of bisphenol A (BPA) in drinks and fruit using dummy surface molecularly imprinted polymer (DSMIP) as a solid-phase extraction (SPE)-enrichment and separation sorbent coupled with high-performance liquid chromatography (HPLC). Tetrabromobisphenol A (TBBPA), whose structure is similar to BPA, was selected as a dummy template molecule. DSMIP has a higher selectivity for BPA than surface non-imprinted polymer (SNIP) when used as sorbents for SPE. Potential factors affecting the extraction efficiency, including conditioning, sample loading, washing and elution, and the breakthrough volume were optimised. Under the optimum experimental conditions, the recoveries of BPA in drinks and fruit were in the range from 98% to 105% with relative standard deviations (RSDs) below 7%, and a limit of detection (LOD) of 3 ng ml^?1. The developed extraction protocol eliminated the effect of template leakage on quantitative analysis and could be applied to the trace determination of BPA in complicated functional samples.     

罐头食品中双酚A和双酚F环氧衍生物残留的高效液相色谱分析

建立了一种高效液相色谱分析罐头食品中双酚A(BPA)和双酚F(BPF)环氧衍生物的方法。样品经微波辅助萃取后过PPL(填料为苯乙烯-二乙烯苯(SDVB)聚合物)固相萃取柱进行净化试验。结果表明,微波辅助萃取法的提取效果理想;采用PPL固相萃取回收率在73.26%~104.98%,除杂效果明显。将微波辅助—PPL固相萃取净化法应用于多种食品进行分析,结果表明该方法适用于食品中双酚A和双酚F环氧衍生物残留分析。     

Effects of Riboflavin Photosensitization on the Degradation of Bisphenol A (BPA) in Model and Real-Food Systems

ABSTRACT:  Effects of riboflavin photosensitizations on the stability of bisphenol A (BPA), a well-known endocrine disrupting chemical, were studied in model and real-food systems by high-performance liquid chromatography (HPLC). Concentration of BPA was significantly decreased under light exposure ( P < 0.05) as the concentration of riboflavin increased while those without riboflavin under light or those with riboflavin in the dark did not change significantly ( P > 0.05). Addition of 50, 100, and 200 μM sodium azide significantly increased the stability of BPA in riboflavin photosensitization with concentration dependent manner ( P < 0.05), implying that a singlet oxygen or type II pathway played a role in the photodegradation of BPA. Stability of BPA in riboflavin was significantly increased in the presence of high concentration of tert -butanol, a hydroxyl radical quencher, under light storage for 80 min, indicating hydroxyl radicals were involved and contributed to the degradation of BPA, at least in part. Availability of riboflavin photosensitization on the photodegradation of BPA was tested in 2 canned tea beverages with different phenolic contents. BPA was more stable in the beverage sample with higher total phenolic contents and free radical scavenging ability. The photodegradation of BPA in riboflavin photosensitization can be an efficient way to decrease the concentration of BPA from environmental or food systems.