Ultrasound enhanced butyric acid-lauric acid designer lipid synthesis: Based on artificial neural network and changes in enzymatic structure

Ultrasound is a green technology for intensifying enzymatic reactions. In this study, an ultrasonic water bath with equipment parameters of 28 kHz, 1750.1 W/m², 60% duty cycle was used to assist the synthesis of butyric acid-lauric acid designer lipid (BLDL), which was catalyzed by Lipozyme 435. A convincing three-layer feed-forward artificial neural network (ANN) model was established (R² = 0.949, RMSE = 4.759, ADD = 7.329) to accurately predict the optimal parameters combination, which was described as 13.72 mL reaction volume, 15.49% enzyme loading, 0.253 substrate molar ratio (tributyrin/lauric acid), 56.58 °C reaction temperature and 120 min reaction time. The ultrasonic assistance increased actual butyric acid conversion rate by 11.38%, and also enhanced the consumption rate of tributyrin and lauric acid during the reaction. Meanwhile, the esterification activity of Lipozyme 435 was enhanced and its effectiveness up to 6 cycles. Structurally, ultrasound assistance significantly disrupted the secondary structure of the Lipozyme 435: reduced the content of α-helices, increased the content of β-sheet and β-turn. In addition, sonication caused an increase in crevice and micro-damage on the surface of the immobilized enzyme. In conclusion, low-intensity ultrasound at 28 kHz improved the synthesis efficiency of BLDL, which was scientifically predicted by ANN model, and the change of enzyme structure may be the vital reason for ultrasound enhanced reaction. However, the effect of ultrasound on immobilized enzymes’ activity needs to be further explored.     

聚丙烯酰胺与混合表面活性剂的相互作用

通过粘度和紫外吸收光谱的测定，研究了ＰＡＭ与Ｒ１２ＳＯ３Ｎａ－Ｒ１１ＣＯＯＮａ混合表面活性剂之间的相互作用，结果表明，ＰＡＭ可与混合表面活性剂形成复合物，从而使体系表现出典型聚电解质的粘度行为。可能的机理是，以疏水力形成的Ｒ１２ＳＯ３＾－—Ｒ１１ＣＯＯＨ（Ｎａ）预胶束或二聚体通过ＰＡＭ－Ｒ１１ＣＯＯＨ间的氢键力相结合。进而使大分子链上带有大量负电荷，静电斥力引起大分子链伸展，因而产生电粘效应。     

Synthesis,Surface Activity,and Antifogging Property of Triethanolamine Monolaurate Ester

Triethanolamine monolaurate ester was synthesized by lauric acid and triethanolamine (TEA) with a molar ratio around 1:1 and the esterification process was investigated and optimized. The esterification product of lauric acid with TEA was characterized by infrared spectra and nuclear magnetic resonance. The surface tension (γ_CMC) at the critical micelle concentration (CMC) was determined, and the antifogging properties of triethanolamine laurate ester on low-density polyethylene (LDPE) films were also measured. The results indicated that the yield of triethanolamine monolaurate ester was more than 69% under optimized esterification condition, the CMC value and γ_CMC of esterification product was 0.91 μg/mL and 22.1 mN/m in aqueous solution at 25 ^oC, respectively. The first-drop time and ten-drop time was 257 and 86 s, respectively, and the antifogging duration of triethanolamine laurate ester on the surface of LDPE film at 60 ^oC was more than 150 h.     

Rheology of highly concentrated anionic surfactants

Surfactant solution flow behavior is of great importance to both the chemical and consumer product industries. Most studies on the flow behavior of surfactant solutions, however, have focused on the dilute regime. Seldom reported is rheology in the highly concentrated regime where typically these surfactants are processed and delivered. First, we present here the phase diagram for the ternary system: water and two anionic surfactants (sodium salt of lauric and oleic acid) at different temperatures. Then, we present both linear viscoelastic and steady shear flow results in the high (70 to 90%) surfactant regime. We find that high values of the shear modulus are directly dependent on the quantity of surfactant crystals and that the formation of a lamellar liquid crystal phase at 45°C affects both modulus and flow of the system. Lamellar crystals create a stiff network resulting in wall slip at large shear strain. Using serrated plates removes slip at the wall and we find a shear rate where microfractures localize in a preferential plane and the material flows. This behavior is reversible.     

三乙醇胺月桂酸单酯的合成、表面活性及防雾性能

用等摩尔比的月桂酸和三乙醇胺为原材料合成了三乙醇胺月桂酸单酯,并对其酯化过程进行了优化,利用红外和核磁共振氢谱对其酯化产物进行了分析和表征．结果表明,三乙醇胺月桂酸单酯的产率高达69%,其在水溶液中的临界胶束浓度及表面张力分别为0.91 μg/mL和22.1 mN/m,其在低密度聚乙烯薄膜上的第一滴流滴时间和十滴流滴时间分别为257和86 s,高温持续期超150 h．