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粉煤灰复合固体酸催化合成乳酸正丁酯的研究 总被引:1,自引:0,他引:1
以乳酸和丁醇为原料,在粉煤灰复合固体酸的催化下,对合成乳酸正丁酯的工艺进行了实验研究,其优惠制备条件为:浸泡硫酸浓度为0.5mol/L,浸泡时间为6h,焙烧温度为550℃,焙烧时间为3h,优化酯化反应条件为:醇酸摩尔比为3∶1,催化剂的用量为乳酸质量的3.0%,反应时间为2h,酯化率可达98.8%。 相似文献
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为测定冷却肉中乳酸含量,建立了冷却肉中乳酸提取及酶电极生物传感器的测定方法。冷却猪肉用1 mol/L高氯酸水溶液匀浆去除蛋白质及脂肪后,以乳酸氧化酶生物传感器检测。检测结果显示,该测定方法线性范围0~0.50 mg/mL乳酸(R=0.999 7),检测限5.0×10-5mg/mL。回收率为97.5%~102.3%,相对标准偏差为2.6%~3.1%,日内测定变异系数(CV)为1.08%,日间测定变异系数为1.26%。该方法应用于冷却猪肉乳酸含量测定获得较好的效果。 相似文献
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《Drug development and industrial pharmacy》2013,39(4):600-610
The purpose of the present work was to elaborate an optimized transdermal therapeutic system for diflunisal. Selection of suitable ingredients was done via solubility and phase behavior studies. Composition of microemulsion (ME) systems consisting of butyl lactate, Brij® 97, Transcutol® and water was optimized using augmented simplex lattice mixture design. The independent variables selected were the percentages of butyl lactate, surfactant mixture and water. The dependent variables were refractive index, pH, conductivity, viscosity, drug solubility in the ME formulation and the ex vivo skin permeation flux. Mathematical equations and response surface plots were used to relate the dependent and independent variables. The statistical validity of the polynomials was established. Optimized formulation factors were selected by desirability approach. The optimized ME formulation was converted into gel using Carbomer® 934. The microemulsion based gel (MBG) showed better spreadability and 5.07-fold increase in the transdermal flux than Carbomer® 934 gel. The in vivo antihyperalgesia assay performed on mice showed significant reduction of the licking time in the treated group compared to the control group. This demonstrated the reliability of the simplex lattice statistical design for predicting optimum ME formulation. The developed MBG proved its in vivo efficiency for transdermal delivery of diflunisal. 相似文献
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NaCl is an important multifunctional ingredient applied in dry-cured ham elaboration. However, its excessive intake has been linked to serious cardiovascular diseases causing a recent increase in the development of reduced salt products. In the present study Listeria monocytogenes and Salmonella, food-borne pathogens which can cross-contaminate post processed products, were spiked with < 100 CFU/g on slices of both standard (S) and NaCl-free processed (F) (elaborated with KCl + potassium lactate instead of NaCl) smoked dry-cured ham. Although L. monocytogenes and Salmonella counts decreased faster in S ham, pathogens were present in both types of non-pressure treated ham during the entire refrigerated storage period (112 days). Pressurisation at 600 MPa for 5 min caused the elimination of both pathogens in S ham after 14 days. In contrast, Salmonella and L. monocytogenes were present in F ham until days 28 and 56, respectively, indicating that the NaCl-free processed dry-cured ham had lower stability than standard smoked dry-cured ham. 相似文献
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The aim of the present study was to determine the survival of Salmonella Typhimurium adapted with sodium lactate (NaL), potassium lactate/sodium acetate mixture (KL/NaA) or sodium acetate (NaA) in simulated gastric fluid (SGF) and during heat treatment. NaL-, KL/NaA- and NaA-adapted cells were prepared by incubating in tryptic soy broth (TSB) containing these salts at 5, 5 and 3% (w/v) concentration levels, respectively, for 24 h at 37 °C. The Baranyi model was used to compare the growth kinetic parameters of adapted cells. The acid and heat resistance of adapted cells were determined by incubating in SGF (pH 2.04) at 37 °C and in TSB at 55.8, 57.8 and 59.8 °C, respectively. Adapted cells had significantly (P < 0.05) longer lag phase duration (LPD) and slower maximum growth rate (MGR) than non-adapted cells. The acid resistance of KL/NaA-adapted cells was not significantly (P > 0.05) different from that of non-adapted cells. NaL-adapted cells were more susceptible to the low pH environment, whereas NaA-adapted cells showed enhanced acid resistance compared to non-adapted and other adapted cells. Unlike acid resistance, both NaL- and NaA-adapted cells showed enhanced heat resistance with increased D-values, regardless of treatment temperatures. Thus, this study indicates that adaptation of S. Typhimurium to 5% NaL or 3% NaA could enhance their ability to survive thermal processes or in the human stomach, possibly increasing the risk of Salmonella outbreaks. 相似文献
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Fumi Osawa Toshio Fujii Takehisa Nishida Nobuki Tada Toru Ohnishi Osamu Kobayashi Toshihiro Komeda Satoshi Yoshida 《Yeast (Chichester, England)》2009,26(9):485-496
Industrial production of L ‐lactic acid, which in polymerized form as poly‐lactic acid is widely used as a biodegradable plastic, has been attracting world‐wide attention. By genetic engineering we constructed a strain of the Crabtree‐negative yeast Candida boidinii that efficiently produced a large amount of L ‐lactic acid. The alcohol fermentation pathway of C. boidinii was altered by disruption of the PDC1 gene encoding pyruvate decarboxylase, resulting in an ethanol production that was reduced to 17% of the wild‐type strain. The alcohol fermentation pathway of the PDC1 deletion strain was then successfully utilized for the synthesis of L ‐lactic acid by placing the bovine L ‐lactate dehydrogenase‐encoding gene under the control of the PDC1 promoter by targeted integration. Optimizing the conditions for batch culture in a 5 l jar‐fermenter resulted in an L ‐lactic acid production reaching 85.9 g/l within 48 h. This productivity (1.79 g/l/h) is the highest thus far reported for L ‐lactic acid‐producing yeasts. DDBJ/EMBL/GenBank nucleotide database with Accession Nos. AB440630 and AB440631. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献