Development of a Pichia pastoris whole-cell biocatalyst with overexpression of mutant lipase I PCLG47I from Penicillium cyclopium for biodiesel production

Penicillium cyclopium lipase I (PCL) is a thermolabile triacylglycerol lipase with very low activity against monoacylglycerols, and there have been no reports on the transesterification of oil to produce biodiesel. A mutant PCL^G47I with an improved thermostability was previously obtained through replacing Gly47 with Ile in PCL. In this study, a novel Pichia pastoris whole-cell biocatalyst (WCB) with overexpression of PCL^G47I was constructed and characterized for biodiesel production from soybean oil. The optimum conditions for biodiesel preparation were 1 g soybean oil, 1 : 2 initial oil/methanol molar ratio with 3 times methanol addition of 1 : 0.75 oil/methanol molar ratio at 4 h intervals, 7% water content, 400 U lipase, temperature of 25 °C, and reaction time of 20 h. Under the optimum conditions, the FAME yield reached 60.7% and remained 47.3% after 4 batch cycles, and no glycerol was generated as a byproduct. These findings indicated that this WCB is a promising biocatalyst for biodiesel production in a relatively cost-effective manner. Additionally, the resulting enzymatic process may provide a potential method for biodiesel production at an industrial scale.

Biodiesel is efficiently produced by a lipase whole-cell biocatalyst with high activity and thermostability at low temperature.     

Detection of resveratrol by phosphorescence quantum dots without conjunction and mutual impact exploration

In this study, a convenient and sensitive method for the detection of resveratrol was established based on phosphorescence quenching of resveratrol for MPA-capped Mn:ZnS QDs. The quenching intensity was in proportion to the concentration of resveratrol within a certain range. Under optimal conditions, the present assay was valid for detecting resveratrol in the range from 0.03 μM to 14 μM with a detection limit of 0.01 μM. The mechanism of action was also explored, and its application in actual samples was also demonstrated with satisfactory results. This study aims to provide a convenient method for the detection of resveratrol.

In this study, a convenient and sensitive method for the detection of resveratrol was established based on phosphorescence quenching of resveratrol for MPA-capped Mn:ZnS QDs.     

Biological effect of food additive titanium dioxide nanoparticles on intestine: an in vitro study

Titanium dioxide nanoparticles (TiO₂ NPs) are widely found in food‐related consumer products. Understanding the effect of TiO₂ NPs on the intestinal barrier and absorption is essential and vital for the safety assessment of orally administrated TiO₂ NPs. In this study, the cytotoxicity and translocation of two native TiO₂ NPs, and these two TiO₂ NPs pretreated with the digestion simulation fluid or bovine serum albumin were investigated in undifferentiated Caco‐2 cells, differentiated Caco‐2 cells and Caco‐2 monolayer. TiO₂ NPs with a concentration less than 200 µg ml^–1 did not induce any toxicity in differentiated cells and Caco‐2 monolayer after 24 h exposure. However, TiO₂ NPs pretreated with digestion simulation fluids at 200 µg ml^–1 inhibited the growth of undifferentiated Caco‐2 cells. Undifferentiated Caco‐2 cells swallowed native TiO₂ NPs easily, but not pretreated NPs, implying the protein coating on NPs impeded the cellular uptake. Compared with undifferentiated cells, differentiated ones possessed much lower uptake ability of these TiO₂ NPs. Similarly, the traverse of TiO₂ NPs through the Caco‐2 monolayer was also negligible. Therefore, we infer the possibility of TiO₂ NPs traversing through the intestine of animal or human after oral intake is quite low. This study provides valuable information for the risk assessment of TiO₂ NPs in food. Copyright © 2015 John Wiley & Sons, Ltd.     

Transmission Risk from Imported Plasmodium vivax Malaria in the China–Myanmar Border Region

Malaria importation and local vector susceptibility to imported Plasmodium vivax infection are a continuing risk along the China–Myanmar border. Malaria transmission has been prevented in 3 border villages in Tengchong County, Yunnan Province, China, by use of active fever surveillance, integrated vector control measures, and intensified surveillance and response.     

Facile morphology control of 3D porous CeO2 for CO oxidation

3D porous CeO₂ with various morphologies was successfully synthesized via a facile precipitation using glycine as the soft bio-template. During the synthesis, it was demonstrated that the morphology of CeO₂ depended on the molar ratio of reactants. Furthermore, the catalytic performance towards CO oxidation of the as-synthesized CeO₂ with different morphologies was investigated. CeO₂ with a bowknot shape showed excellent catalytic performance, giving complete CO conversion at 370 °C, due to its properties of much higher oxygen vacancies, loosely packed pore structure and larger specific surface area.

Different morphologies of CeO₂ were obtained via a green and facial method, which realized CO complete conversion at 370 °C.     

Insight into the significant roles of microstructures and functional groups on carbonaceous surfaces for acetone adsorption

To understand the roles of pore structures and functional groups on acetone adsorption, activated carbons (ACs) with different properties were obtained by surface modification. XRD, SEM, TEM and nitrogen adsorption were used to identify the structural characteristics of the ACs, while TG-DTA, FTIR, XPS and Boehm titration were applied to analyse the surface chemistries. The microporous surface areas showed a positive linear correlation to the acetone adsorption amounts, and increasing the carboxylic groups could improve the uptake of strongly adsorbed acetone. HNO₃ modified AC (AC-N) was found to exhibit an excellent adsorption capacity of 5.49 mmol g⁻¹, which might be attributed to the developed microporous structures and abundant carboxylic groups. The desorption activation energies (E_d) of strongly adsorbed acetone on AC-N and AC were both determined to be 81.6 kJ mol⁻¹, indicating the same adsorption sites on different activated carbons, suspected to be carboxylic groups. The possible adsorption mechanism of acetone on carbonaceous surfaces was also proposed.

To understand the roles of pore structures and functional groups on acetone adsorption, activated carbons (ACs) with different properties were obtained by surface modification.     

不同方法对食源性致病菌耐药性监测研究

目的了解江苏地区食源性致病菌的常用抗菌药耐药谱,评价不同药敏方法在致病菌耐药性监测中的适用性。方法用Etest和微量肉汤稀释法,对江苏省2012-2014年食源性疾病常规监测检出的金黄色葡萄球菌、副溶血性弧菌、沙门菌菌株进行药敏鉴定。结果金黄色葡萄球菌对红霉素的耐药率最高,其次为复方磺胺甲噁唑和四环素,且有多重耐药;副溶血性弧菌除对四环素和复方磺胺甲噁唑有一定的耐药,对其他6种革兰氏阴性菌抗生素均敏感。沙门菌对萘啶酸的耐药率超过50.0%。两种方法药敏检测结果对不同抗生素符合率有差异,但符合率均80%。结论 Etest和微量肉汤稀释法有较好的一致性,但所需时间及操作要求有差异,可根据实际需要进行选择。     

Analysis of oxidation degree of graphite oxide and chemical structure of corresponding reduced graphite oxide by selecting different-sized original graphite

The thermal exfoliation and reduction of graphite oxide (GO) is the most commonly used strategy for large-scale preparation of graphene, and the oxidation degree of GO would influence the chemical structure of prepared graphene, thereby affecting its final physical and chemical properties. In addition to serving as the precursor for synthesizing graphene, GO also possesses great potential for various important applications owing to its abundant oxygen-containing groups and hybrid electronic structure. Therefore, systematically studying the influencing factors on the oxidation degree of GO and clarifying the effect of oxidation degree on the corresponding graphene is particularly important. Herein, we have studied the effect of the lateral size of the original graphite on the oxidation degree of GO in order to control the oxidation degree of GO. GOs with different degrees of oxidation were synthesized using a modified Hummers method. The results of X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and Raman spectroscopy revealed that decreased lateral size of the original graphite would lead to increased oxidation degree of GO. Furthermore, the interlayer spacing of the GO samples achieved 0.9–1.0 nm, which indicated that the modified Hummers method could make well oxidized graphite. The corresponding reduced graphite oxide (rGO) was also prepared by low-temperature exfoliation of GO at 140 °C under ambient atmosphere. It was found that a larger lateral size of GO resulted in rGO with fewer oxygen-containing functional groups, but a smaller lateral size of graphite possessed a higher exfoliation degree with a larger specific surface area. More importantly, the relationship between binding energy (E_B) of photoelectron of C atom in oxygen-containing groups and the number of oxygen-containing groups in GO and rGO samples was analyzed theoretically.

The thermal reduction of GO is the most commonly used strategy for preparation of rGO, and the oxidation degree of GO would influence the chemical structure of prepared rGO, thereby affecting its physical and chemical properties.