酵母脂肪酶酶促合成虾青素琥珀酸酯及优化

研究了酵母脂肪酶在有机溶剂中以琥珀酸酐为酰化试剂酯化合成虾青素琥珀酸酯。液相色谱质谱联用检测表明,酯化产物中既有虾青素单酯也有虾青素二酯。对酶促反应脂肪酶、反应介质、反应底物摩尔比、反应温度等酯化影响因素进行了详细探讨和优化。在所选的几种脂肪酶中,假丝酵母脂肪酶(Candida sp.)的催化活性最好,二甲基亚砜为适宜的反应溶剂,最佳反应温度为45℃。底物摩尔比是决定反应能否进行的关键因素,底物摩尔比为40以上,反应才能进行,摩尔比达到800时,虾青素转化率达到90%以上。底物摩尔比还显著影响产物中单酯和二酯分布,高摩尔比下二酯才能产生。对体系初始含水量和酶量的影响进行了优化。实验结果表明酶法合成虾青素琥珀酸酯具有很好的可行性。     

聚丁二酸丁二醇酯/水滑石纳米复合材料的制备及性能研究

采用双螺杆挤出机制备了聚丁二酸丁二醇酯/水滑石(PBS/HT)纳米复合材料,并详细研究了复合材料的形貌及分散、结晶和熔融行为,晶体结构和球晶形态以及力学性能。采用SEM、TEM、DSC、XRD、POM和DMA进行了表征测试,结果表明层状水滑石纳米粒子较好地分散在PBS基体中,加入HT具有明显的异相成核能力,显著地提高了PBS的结晶温度。偏光显微镜结果显示,随着HT加入量的增加PBS球晶密度增加,球晶尺寸细化。HT添加量为1%(质量分数)时复合材料的拉伸强度增大,随着HT加入量增加断裂伸长率下降而弹性模量增加。动态机械测试表明复合材料的储能模量显著提高。     

不同天然色素对PBS性能的影响

将从石榴皮、大黄和黄芩中提取的3种色素以不同的质量比与可生物降解的聚丁二酸丁二醇酯(PBS)共混,制备了多种比例的PBS/色素复合材料,研究了上述3种PBS/色素材料的结晶性和热稳定性;同时研究了色素的添加对PBS力学性能和抗菌性的影响。结果表明,添加3种色素对PBS的结晶形态影响不大,但是使晶粒尺寸变小,结晶度增加;使PBS的热稳定性有所提高,但对综合力学性能影响不大;3种色素都使PBS材料具有良好的抗菌性。     

Breeding of high malate‐producing diploid sake yeast with a homozygous mutation in the VID24 gene

Malate is an important taste component of sake (a Japanese alcoholic beverage) that is produced by the yeast Saccharomyces cerevisiae during alcoholic fermentation. A variety of methods for generating high malate‐producing yeast strains have been developed to date. We recently reported that a high malate‐producing strain was isolated as a mutant sensitive to dimethyl succinate (DMS), and that a mutation in the vacuolar import and degradation protein (VID) 24 gene was responsible for high malate productivity and DMS sensitivity. In this work, the relationships between heterozygous and homozygous mutants of VID24 and malate productivity in diploid sake yeast were examined and a method was developed for breeding a higher malate‐producing strain. First a diploid yeast was generated with a homozygous VID24 mutation by genetic engineering. The homozygous integrants produced more malate during sake brewing and grew more slowly in DMS medium than wild‐type and heterozygous integrants. Thus, the genotype of the VID24 mutation influenced the level of malate production and sensitivity to DMS in diploid yeast. Then a homozygous mutant from a heterozygous mutant was obtained without genetic engineering by ultraviolet irradiation and culturing in DMS with nystatin enrichment. The non‐genetically modified sake yeast with a homozygous VID24 mutation exhibited a higher level of malate productivity than the parent heterozygous mutant strain. These findings provide a basis for controlling malate production in yeast, and thereby regulating malate levels in sake. Copyright © 2016 The Institute of Brewing & Distilling     

拉伸形变作用下PLA/PBS增韧共混物力学性能研究

通过叶片挤出机对聚乳酸/聚丁二酸丁二醇酯（PLA/PBS）及添加剂进行塑化共混后制备复合增韧体系,研究不同PLA/PBS配比、挤出机转速以及添加剂种类对共混物力学性能的影响。结果表明,随着PBS含量的增加,PLA/PBS共混物的拉伸强度变化不大,而韧性明显提高;当叶片挤出机转速为75 r/min,改性剂邻苯二甲酸二仲辛酯(DCP)含量为0.05 %(质量分数,下同),马来酸酐接枝聚丙烯（PP-g-MAH)含量为1.5 %时,共混物具有最佳力学性能;PLA与PBS相容性较差,但叶片挤出机提供的拉伸力场迫使分散相分散均匀,尺度较小。     

聚丁二酸丁二醇酯的酶促降解研究

以聚丁二酸丁二酯（PBS）薄片为降解底物,利用角质酶对其进行降解研究,考察PBS的酶促降解行为。利用扫描电子显微镜、差示扫描量热仪和热重分析仪等方法对降解前后的PBS薄片进行了表征分析,并进一步采用质谱仪对降解产物进行分析。结果表明,在酶浓度2.5 U/mL、反应温度37 ℃以及pH 7.4的条件下,经16 h降解PBS薄片的降解率可达93.88 %,在降解时间为2 h时有最大降解速率32.97 μg/cm2·h;PBS薄片有片层脱落降解的现象,促进了角质酶的降解作用;随降解时间的延长,PBS相对结晶度逐渐降低,热稳性也呈现下降趋势;PBS被降解成单体或寡聚物。     

Effect of isocyanate‐modified fumed silica on the properties of poly(butylene succinate) nanocomposites

Using the grafting method on a silica surface with PBS molecules, we prepared novel poly(butylene succinate) (PBS)/silica nanocomposites to enhance dispersibility and interfacial adhesion between silica particles and the PBS matrix, and also investigated the effects of silica‐g‐PBS on the PBS matrix using differential scanning calorimetry, thermogravimetric analysis, transmission electron microscopy, a tensile testing machine, and rheometry. The thermal stability, mechanical properties, and rheological properties of PBS nanocomposites containing silica‐g‐PBS was remarkably improved because of the surface characteristics of the silica grafted with PBS molecules, which provided good compatibility and dispersion. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biodegradable plastic composites from corn gluten meal

BACKGROUND: Utilisation of naturally occurring polymers as substitutes for non‐biodegradable synthetic polymers derived from non‐renewable resources is a key component of sustainable polymer technology. The aim of this study was to make thermoformable, biodegradable plastics from protein‐rich corn gluten meal (CGM) in combination with a synthetic biodegradable polyester. RESULTS: CGM plasticised with 1,2‐propylene glycol was blended at 150 °C with Skygreen SG100 aliphatic polyester and wood fibre, and injection moulded to give composites with tensile strength and water resistance superior to those of the protein component of CGM. Experimental design software was used to generate composite formulations with the limits (component, proportion as wt%) plasticised CGM (A), 10–80; Skygreen SG100 (B), 10–85; wood fibre (C), 0–10. Composites with A:B:C and A:B:C showed a glass transition at ? 20 °C associated with the SG100 component; composites with more than 15 wt% CGM showed an additional glass transition for the plasticised CGM component. SG100 imparted water resistance and tensile strength, while CGM and wood fibre increased tensile modulus. CONCLUSION: The low‐cost industrial by‐product CGM, derived from an abundant renewable resource, can be incorporated into SG100 to give readily biodegradable, thermoformable materials. Composites with up to 30 wt% CGM have moderately high tensile strength, elongation at break and water resistance. Copyright © 2007 Society of Chemical Industry     

生物可降解聚丁二酸乙二醇酯的合成与降解性能研究

以丁二酸和乙二醇为原料,直接熔融聚合,合成了高相对分子量的聚丁二酸乙二醇酯(PES),用FTIR,1H-NMR表征其结构;考察了不同聚酯反应催化剂对其聚合反应的影响,结果表明:三氧化二锑的催化效果是最佳的。同时,利用酶降解和体外水解的方法,对聚合物降解性能进行研究,结果表明:PES是一种可生物降解的聚合物,且在体外具有一定的降解性。