Studies on epoxidation reaction of oleic acid catalyzed by lipase immobilized by different methods

在H2O2存在的条件下，脂肪酶可以有效催化不饱和脂肪酸上双键的环氧化反应，制备具有广泛用途的环氧植物油和环氧脂肪酸，但反应体系中的H2O2和反应生成的过氧酸导致酶活性损失较大，需通过固定化提高酶的稳定性。本文采用微球和纳米纤维两类载体固定化脂肪酶，以油酸环氧化为模型反应分别构建非水相反应体系和油水两相反应体系，考察固定化脂肪酶催化油酸环氧化反应的活性和重复使用稳定性，并与葡萄糖氧化酶偶联，考察偶联反应体系的活性和操作稳定性，具体如下： （1）考察不同类型游离脂肪酶催化油酸环氧化反应的活力，以南极假丝酵母脂肪酶B（Candida Antarctica Lipase B，CALB）的活力最高，因此选用CALB催化油酸环氧化反应。 （2）分别用8种具有不同孔径、亲疏水性和功能基团的微球吸附或偶联脂肪酶。CALB在介孔聚苯乙烯微球PST30上负载量最高为100.7 mg/g，超大孔聚苯乙烯微球PST固定化CALB的比活力最高，在非水相和油水两相体系中的比活力分别是Novozym 435的1.8倍和7.3倍，且重复使用性能与Novozym 435相当。 （3）在聚氨酯纳米纤维表面固定化CALB，又利用中空聚氨酯纳米纤维包埋CALB，中空纳米纤维包埋酶的比活力更高，在非水相体系和油水两相体系中的比活力分别是游离酶的38.1倍和25.2倍，是Novozym 435比活力的50.3倍和110.8倍。 （4）微球和纳米纤维固定化脂肪酶CALB分别与游离葡萄糖氧化酶偶联催化油酸的环氧化反应，以中空纳米纤维固定化CALB催化偶联反应的活力最高，且具有良好的重复使用稳定性，重复使用40次以后活力收率仍可达到60%

聚苯乙烯微球吸附脂肪酶催化油酸环氧化的研究

南极假丝酵母脂肪酶B(Candida antarctica Lipase B,CALB)在H2O2的存在下可以有效地催化不饱和脂肪酸上双键的环氧化反应,制备出具有广泛用途的环氧植物油和环氧脂肪酸,但反应体系中的H2O2和反应生成的过氧酸对酶有严重的失活作用,需通过固定化提高酶稳定性。本文选用具有不同亲疏水性和孔径的聚苯乙烯微球,通过吸附法固定化CALB,并构建了非水相和油/水两相体系作为CALB催化油酸环氧化反应的介质。结果表明,固定化CALB在非水相体系中具有较高的活力,而在油/水两相体系中重复使用性能较好;CALB在疏水性介孔聚苯乙烯微球PST30上具有最高的酶负载量(100.7mg/g),在疏水性超大孔聚苯乙烯微球PST上表现出最高的催化活力和重复使用稳定性,其在非水相和两相反应体系中的催化活力分别是Novozym 435的1.8倍和7.3倍,重复使用次数与Novozym 435相当,在油/水两相体系中重复使用至第2次还出现独特的活力升高现象

聚苯乙烯微球吸附脂肪酶催化油酸环氧化的研究

南极假丝酵母脂肪酶B（Candida antarctica Lipase B,CALB）在H2O2的存在下可以有效地催化不饱和脂肪酸上双键的环氧化反应,制备出具有广泛用途的环氧植物油和环氧脂肪酸,但反应体系中的H2O2和反应生成的过氧酸对酶有严重的失活作用,需通过固定化提高酶稳定性。本文选用具有不同亲疏水性和孔径的聚苯乙烯微球,通过吸附法固定化CALB,并构建了非水相和油/水两相体系作为CALB催化油酸环氧化反应的介质。结果表明,固定化CALB在非水相体系中具有较高的活力,而在油/水两相体系中重复使用性能较好;CALB在疏水性介孔聚苯乙烯微球PST30上具有最高的酶负载量（100.7mg/g）,在疏水性超大孔聚苯乙烯微球PST上表现出最高的催化活力和重复使用稳定性,其在非水相和两相反应体系中的催化活力分别是Novozym 435的1.8倍和7.3倍,重复使用次数与Novozym 435相当,在油/水两相体系中重复使用至第2次还出现独特的活力升高现象

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

Prediction of Energy Resolution in the JUNO Experiment

International audienceThis paper presents the energy resolution study in the JUNO experiment, incorporating the latest knowledge acquired during the detector construction phase. The determination of neutrino mass ordering in JUNO requires an exceptional energy resolution better than 3% at 1 MeV. To achieve this ambitious goal, significant efforts have been undertaken in the design and production of the key components of the JUNO detector. Various factors affecting the detection of inverse beta decay signals have an impact on the energy resolution, extending beyond the statistical fluctuations of the detected number of photons, such as the properties of liquid scintillator, performance of photomultiplier tubes, and the energy reconstruction algorithm. To account for these effects, a full JUNO simulation and reconstruction approach is employed. This enables the modeling of all relevant effects and the evaluation of associated inputs to accurately estimate the energy resolution. The study reveals an energy resolution of 2.95% at 1 MeV. Furthermore, the study assesses the contribution of major effects to the overall energy resolution budget. This analysis serves as a reference for interpreting future measurements of energy resolution during JUNO data taking. Moreover, it provides a guideline in comprehending the energy resolution characteristics of liquid scintillator-based detectors

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies