Fatty acid hydratase for value-added biotransformation:A review

The synthesis of hydroxy fatty acids(HFAs) from renewable oil feedstock by addition of water onto C_C bonds has attracted great attention in recent years. Given that selective asymmetric hydration of non-activated C_C bonds has been proven difficult to achieve with chemical catalysts, enzymatic catalysis by fatty acid hydratases(FAHs) presents an attractive alternative approach to produce value-added HFAs with high regio-, enantioand stereospecificity, as well as excellent atom economy. Even though FAHs have just been investigated as a potential biocatalyst for a decade, remarkable information about FAHs in different aspects is available; however, a comprehensive review has not been archived. Herein, we summarize the research progresses on biochemical characterization, structural and mechanistic determination, enzyme engineering, as well as biotechnological application of FAHs. The current challenges and opportunities for an efficient utilization of FAHs in organic synthesis and industrial applications are critically discussed.     

Rational Engineering of Hydratase from Lactobacillus acidophilus Reveals Critical Residues Directing Substrate Specificity and Regioselectivity

Enzymatic conversion of fatty acids (FAs) by fatty acid hydratases (FAHs) presents a green and efficient route for high-value hydroxy fatty acid (HFA) production. However, limited diversity was achieved among HFAs, to date, with respect to chain length and hydroxy position. In this study, two highly similar FAHs from Lactobacillus acidophilus were compared: FA-HY2 has a narrow substrate scope and strict regioselectivity, whereas FA-HY1 utilizes longer chain substrates and hydrates various double-bond positions. It is revealed that three active-site residues play a remarkable role in directing substrate specificity and regioselectivity of hydration. If these residues on FA-HY2 are mutated to the corresponding ones in FA-HY1, a significant expansion of substrate scope and a distinct enhancement in hydration of double bonds towards the ω-end of FAs is observed. A three-residue mutant of FA-HY2 (TM-FA-HY2) displayed an impressive reversal of regioselectivity towards linoleic acid, shifting the ratio of the HFA regioisomers (10-OH/13-OH) from 99:1 to 12:88. Notable changes in regioselectivity were also observed for arachidonic acid and for C₁₈ polyunsaturated fatty acid substrates. In addition, TM-FA-HY2 converted eicosapentaenoic acid into its 12-hydroxy product with high conversion at the preparative scale. Furthermore, it is demonstrated that microalgae are a source of diverse FAs for HFA production. This study paves the way for tailor-made FAH design to enable the production of diverse HFAs for various applications from the polymer industry to medical fields.     

Synthesis and Properties of La2O3-Doped 8 mol% Yttria-Stabilized Cubic Zirconia

In this study, 8 mol% yttria-stabilized cubic zirconia (8YSZ) powder as a matrix material and 0-15 wt.% La₂O₃ powder as an additive were used to determine the effect of La₂O₃ addition and its amount on the phase stability, microstructure, sintering, and mechanical properties of 8YSZ. Colloidal processing was used to mix the powders uniformly and to obtain a homogenous microstructure. XRD results showed the existence of only a cubic crystal structure for 1 and 5 wt.% La₂O₃ addition amounts. However, La₂Zr₂O₇ with a hexagonal and cubic crystal structure was observed in 8YSZ specimens doped with 10 and 15 wt.% La₂O₃. Further, up to 5 wt.% La₂O₃ was completely dissolved in the crystal structure of the specimens; however, above 5 wt.%, La₂O₃ reacted with 8YSZ at high temperatures and formed pyrochloric La₂Zr₂O₇. Grain size measurements revealed that the grain size of 8YSZ increased up to 1 wt.% La₂O₃ addition, and then decreased beyond this amount. The hardness and fracture toughness of 8YSZ decreased and increased, respectively, with the increasing La₂O₃ amount.     

超声波振动塑化原理模型及装置

探讨了振动对聚合物熔体的体积效应、剪切塑化作用。构建了新型熔融塑化理论，并根据塑化原理设计了多功能流变性能测试装置．对聚合物流变性能进行了测试，取得好的塑化效果，验证了塑化模型的可行性．     

复合诱变红曲霉选育红色素高产菌株

以紫红曲霉No.1为出发菌株，通过紫外线诱变处理，获得一株色价较高的菌株No．1-18，该菌株红色素含量比No.1提高1倍；进而对其进行紫外一氯化锂复合处理，诱变株经筛选，最后得到一株具有稳定遗传性的红色素高产菌株No.1-18—42，用大米粉摇瓶培养基进行液态发酵，连续传代5次，发酵液中红色素量稳定在18．2U／mL左右，红色素产量比No．1—18提高了30％．     

提高退火炉用圆盘构件热疲劳寿命的研究

用有限元方法，对硅钢片卷材退火炉的圆盘构件进行了高温复杂交变热应力的分析，并对圆盘构件的裂纹扩展过程进行了计算机仿真，得到了温度-应力曲线和一组结构最优的圆盘构件的几何形状，从而提高了炉底板的使用寿命．     

基于Intranet的零件库管理信息系统

通过分析某公司零件库的工作流程，对零件库管理信息系统应具有的基本功能进行了描述、设计和模块划分，并对模块功能做出说明，在此基础上介绍了一个基于Intranet的零件库管理信息系统的体系结构及技术实现．     

PC机对五坐标数控钻床控制与通信的实现

研究了一种关于五坐标数控钻床的控制与通信系统．侧重介绍了人机交互、CPU与上位机串行通信、上位机与下位机之间并行通信及数据的存储．该系统是基于PC的分层控制系统，不仅应用于数控钻床，且进一步扩充了分层控制的应用领域．     

论建设人文与科学互渗的现代新型课程体系

论述了人文精神与科学精神的内涵和特点,并阐述了两者的内在关系。根据这一关系，提出了高校现代课程设计的思路，强调不同专业的课程设计都应兼顾人文精神与科学精神的互渗和融合，只可有所侧重而不能偏废．     

Extrusion of poly(ether imide) foams using pressurized CO2: Effects of imposition of supercritical conditions and nanosilica modifiers

Foams of an engineering plastic, poly(ether imide), were extruded using a single screw extruder employing pressurized CO₂ as the blowing agent. The porosity, pore size distributions, and the density of the foams were especially affected by the pressure drop, the pressure loss rate, and temperature at the die. Significant increases in porosity and pore size and corresponding decreases in density were observed when the pressure imposed on CO₂ became greater than the critical pressure values of CO₂ (i.e., the temperature was always greater than the critical temperature of the CO₂ in the extruder and the die). The viscoelastic material functions of the extruded foams depended especially on the density of the foam, with the elastic modulus increasing with density. The incorporation of nanosilica particles in the 0.08–0.6% by weight range increased only the density of the foam and did not provide any benefits in controlling of the nucleation rate and the pore size distribution, presumably due to their poor dispersibility and agglomerated state in the single screw extruder. POLYM. ENG. SCI., 54:2064–2074, 2014. © 2013 Society of Plastics Engineers