Fruit softening correlates with enzymatic activities and compositional changes in fruit cell wall during growing in Lycium barbarum L.

The present study aims to examine fruit cell wall-associated fruit softening in Lycium barbarum L. by the microstructure of the fruit cells and the changes in the contents of cell wall components, molecular weights of cell wall polysaccharides and the activities of related cell wall degrading enzymes at different development stages of L. barbarum L. fruit. Fruit firmness significantly declined during ripening, with the greatest reduction between the 28 and 35 days stages. The decrease in firmness correlated with an extensively deformed microstructure in the parenchyma tissues and positively correlated with reductions in the contents of fruit cell wall materials and molecular weight in cell wall polysaccharide. Cellulase, α-galactosidase, polygalactosidase and pectin methylesterase showed higher activities during 28 days; whereas, the activities of β-galactosidase were higher during 35 days. These results indicate that cell wall-related processes are a key feature of early softening in L. barbarum L.     

Synergistic effect of high-intensity ultrasound and β-cyclodextrin treatments on browning control in apple juice

This work evaluated the synergistic effects of combined high-intensity ultrasound (HIU) with β-cyclodextrin (β-CD) treatments on inhibiting browning of apple juice and explored the mechanism through simulation system. The combined treatment of 300 W HIU with 0.006 g mL⁻¹ β-CD had a synergistic impact on maintaining juice colour, resulting in a 39.06% reduction in browning degree, only a 36.64% decrease in total phenolic content, and a 17.82% reduction in PPO activity. The inhibition of enzymatic browning in simulated system revealed that HIU suppressed the enzyme (Polyphenol oxidase, PPO) and β-CD inhibited enzyme (PPO) and embedded substrate (polyphenol). The results of spectroscopic analysis showed that the particle-size distribution of PPO narrowed, the content of α-helix in the secondary structure increased, the fluorescence intensity increased, and the maximum wavelength was red-shifted after HIU and β-CD treatment. Changes in structure could further result in PPO activity loss. Hence, the combined treatment could synthetically alleviate the browning of apple juice.     

Effects of Bacillus velezensis zk1 on the physiology and metabolism of peaches

Bacillus velezensis zk1 is the dominant bacterium that causing rot in peaches. However, the mechanisms through that this bacterium causes rot have not been elucidated. Here, we explored the mechanisms of peach decay caused by B. velezensis zk1. The invasion of B. velezensis zk1 in peaches resulted in an increase in glucose and arabinose contents in fruit tissues. Moreover, the relative conductivity of the fruit reached 84% after 4 days of culture with bacterial invasion. With the destruction of cells, the malondialdehyde content increased, whereas the vitamin C, dialdehyde, flavonoid and total phenol contents decreased. Polyphenol oxidase, superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and ammonia lyase activities also decreased. Overall, these findings demonstrated that B. velezensis zk1 infection damaged peach chloroplasts, mitochondria, respiratory chain activity and related free radical scavenging enzyme systems, thereby disrupting the normal physiological metabolism of peaches and causing rot.     

微波辅助孵育法富集麦胚多肽的工艺优化

目的 麦胚孵育过程中蛋白酶将蛋白质水解成肽和氨基酸，多肽具有明确的生理活性和营养调节作用。本研究以麦胚为试验原料，采用微波辅助预处理的方法，研究孵育的温度、时间、pH及料液比4种因素对孵育后的蛋白酶活力及多肽含量的影响。 方法 通过单因素和响应曲面试验进行工艺条件优化。 结果 与未进行微波辅助预处理的样品相比，微波辅助处理（600 W, 10 s）能显著提高孵育后样品中的蛋白酶酶活力（约9.4倍）和肽含量（约3.1倍）。经过微波辅助处理后，孵育温度为51.5℃、pH为4.0、时间为6.33 h、料液比为1:7时，蛋白酶活力达最高为3826.24 U/g；孵育温度为45.0 ℃、pH为4.8、时间为8 h、料液比为1:7时，肽含量达最高为262.63 mg/g。 结论 微波辅助处理能有效的激活麦胚孵育液中的内源性蛋白酶活性，促进蛋白水解反应，显著提高孵育后的肽含量。该研究结果为麦胚多肽的制备新工艺开发提供了研究基础。     

Reactor development for peroxidase catalyzed polymerization and precipitation of phenols from wastewater

Horseradish peroxidase enzyme catalyzes the oxidation of toxic aromatic compounds, especially phenols and aromatic amines, in the presence of hydrogen peroxide. The reaction products polymerize to form high molecular weight materials which readily precipitate from solution; hence, providing a means for the treatment of wastewaters which contain aromatic compounds. The catalytic lifetime of horseradish peroxidase enzyme can be extended by optimizing treatment conditions such as pH and temperature and by maintaining a low instantaneous enzyme concentration in the reaction mixture. The enzyme catalyzed polymerization process was implemented in a continuous stirred tank reactor (CSTR) configuration because reactant and enzyme concentrations are lowered immediately upon entering the reactor causing a reduction in inactivation of HRP through free radical bonding and compound III formation. Catalytic turnovers achieved in single and multiple CSTRs in series were significantly higher than those observed in batch reactors when sufficient retention time was provided.     

Detection of enteroviruses in treated drinking water

This study deals with the routine monitoring of drinking water for the presence of enteroviruses, over a period of 1 year. A rapid and simple method was employed for the simultaneous detection and typing of enteroviruses in large-volume water samples. This included an integrated cell culture/nested PCR approach, followed by restriction enzyme analysis. The two drinking water supplies studied were derived from acceptable quality surface water sources using treatment processes, which conform to international specifications for the production of safe drinking water. Enteroviruses (predominantly coxsackie B viruses) were detected in 11% and 16% of the drinking water samples from two treatment plants, respectively. This study confirms that acceptable water quality indicators do not necessarily reflect the virus content of drinking water.     

Aquatic microbial activity and macrofaunal profiles of an Oklahoma stream

A toxicity assessment was conducted on Skeleton Creek, near Enid, Okla. This creek received effluents from an oil refinery, municipal waste treatment facility, and a fertilizer processing plant. Microbial activity assays, which focused on sediments, included: dehydrogenase, alkaline phosphatase, glucosidase, amylase and protease activity. Microbial electron transport system activity was also measured in overlying waters and sediments. Results were compared to a study conducted at the same time by the U.S. Environmental Protection Agency (EPA) which measured in-stream fish, plankton and benthic communities. In addition, EPA conducted 7-day Ceriodaphnia reproductive toxicity tests and 7-day larval fathead minnow growth tests. Effects occurred below the 3 discharges and similar response patterns were noted between surrogate microbial assays and stream communities. These results highlight the importance and feasibility of multi-tiered test schemes in aquatic toxicity assessments.     

负载型TiO2光催化氧化水中微量环己烷

GC／MS分析结果表明，水中微量环己烷在负载型TiO2光催化氧化作用下生成了环己醇、环己酮等中间产物。当pH值为5．2－8．9时，环己烷光催化氧化过程受溶液pH值的影响较小，反应速率基本保持不变；溶液pH值较低（pH＝2．0）时环己烷的光催化氧化速率减小，而pH值较高（pH=12.0)时则能促进这一过程的进行。溶液中无机阴离子（如SO4^2-)的存在能抑制环己烷的光催化氧化过程，而光照距离的减小（即光强增大）则能加快降解速率。     

麦饭石SRB污泥固定颗粒的稳定性及生物活性实验

针对我国煤矿酸性废水(ACMD)腐蚀性强、锰硫含量高的特点,基于微生物固定化技术,将改性麦饭石与硫酸盐还原菌污泥(SRB)有机结合,制成一种用于处理ACMD的改性麦饭石固定化SRB污泥颗粒。通过进行颗粒对酸碱盐溶液的稳定性试验及对比有无麦饭石颗粒膨胀率、OD600和SO42-的处理效果,探讨颗粒的结构稳定性及改性麦饭石对颗粒结构稳定、生物活性的影响,初步分析颗粒的适用性及可行性。结果表明,颗粒能满足对一般酸度较低ACMD的稳定性要求,有麦饭石颗粒的结构膨胀、基质外泄情况及SO42-去除效果优于无麦饭石颗粒,说明麦饭石对颗粒的结构稳定性、生物活性有一定的积极影响。