Diffuse reflectance fourier transform infrared spectroscopy of triacylglycerol and oleic acid adsorption on synthetic magnesium silicate

Diffuse reflectance fourier transform infrared (FTIR) was used to observe adsorption complexes of triacylglycerol and oleic acid on silica gel and synthetic magnesium silicate. The spectra provide evidence of the nature of the surface interaction. Triacylglycerol was shown to be physically adsorbed to both adsorbents. Oleic acid was physically adsorbed to the silica gel, but both physically and chemically adsorbed to the magnesium silicate. The FTIR spectrum of magnesium silicate that was used to treat a degraded frying oil was similar to that of oleic acid adsorbed on magnesium silicate.     

Fat modification in afuegal’l pitu cheese during ripening by capillary gas chromatography

Free and esterified fatty acids and the major groups of triacylglycerol in Afuega’l Pitu cheese have been identified and quantitated over a maturation period of 60 d by capillary gas chromatography. Levels of lipolysis were slight at the end of ripening, with a total free fatty acid content of 5604 mg/kg of cheese. At the same time, the short-chain esterified fatty acids and short-chain triglyceride contents decreased slightly.     

TLL脂肪酶C末端修饰对其底物选择性的调节作用

本研究以甘油三酯脂肪酶TLL为研究对象,将偏甘油酯脂肪酶AOL的C末端(Y246-H266)与其C末端(I241-P256)替换,获得突变体TLL_CC,并在毕赤酵母X-33中成功地进行了重组表达。乳化橄榄油的水解实验显示,C末端的置换不影响TLL脂肪酶的p H特性,但是TLL_CC的最适反应温度较TLL脂肪酶下降了15℃。这可能意味着长的C末端可以增加酶分子整体的柔性,进而降低其最适反应温度。三油酸甘油酯的水解实验发现,TLL脂肪酶和突变体TLL_CC反应体系中残留的三酯分别为28.31%和48.12%。而酯化合成甘油酯实验显示,TLL_CC催化的反应体系中TAG生成量仅为野生型的56.67%,但DAG的生成量却相同。上述研究表明,TLLC末端的这种置换明显减弱了TLL脂肪酶水解和合成TAG的能力,但并不影响其合成DAG的能力。这说明C末端的氨基酸替换可能对脂肪酶TLL的底物选择性起到调节作用。