不同菌株发酵得到的酵母蛋白营养成分及结构差异分析

Nutritional Composition and Structural Analysis of Yeast Proteins Obtained by Fermentation with Different Strains

为分析5种不同菌株发酵得到的酵母蛋白(Yeast protein,YP)YP-1、YP-2、YP-3、YP-4、YP-5在营养成分及结构上的差异,对其基本营养成分、水解氨基酸含量进行了测定,并通过高效液相色谱-质谱联用测定了游离多肽含量。此外,采用扫描电子显微镜对酵母蛋白的结构进行了表征,激光衍射粒度分析仪对酵母蛋白溶液中的颗粒粒径进行了测定,以及通过傅立叶变换红外光谱仪测定了酵母蛋白的二级结构。结果表明:YP-5中含有的矿物质总含量最高,且每种酵母蛋白的含量有所差异;YP-2的维生素B_(2)含量最高为0.240 mg/100 g,YP-3、YP-4中的维生素PP总含量相差不大;5种酵母蛋白的必需氨基酸(Essential amino acids,EAA)/氨基酸总量(Total amino acids,TAA)的比值都在0.44及以上,EAA/非必需氨基酸(Non-essential amino acids,NEAA)的比值都在0.79及以上,证明了酵母蛋白是一种理想的蛋白质来源;酵母蛋白游离多肽的序列测定显示各组间的多肽表达量差别较大。扫描电子显微镜结果显示酵母蛋白成聚集状态,颗粒直径为2.20~4.01μm。激光衍射粒度分析仪结果显示酵母蛋白溶液颗粒的平均粒径在3~5μm之间,其中,YP-4的平均颗粒粒径最大。此外,二级结构显示5种酵母蛋白酰胺I带都集中在1724 cm^(–1)附近。这些结果可以对酵母蛋白功能性产品的开发提供理论指导。

In order to analyze the differences in nutritional composition and structure of yeast proteins YP-1,YP-2,YP-3,YP-4 and YP-5,which were obtained by fermentation with 5 different yeast strains,and their nutritional composition and hydrolyzed amino acid contents were determined.The free polypeptide of yeast proteins was determined by high performance liquid chromatography-mass spectrometry.In addition,the structure of the yeast proteins was characterized by scanning electron microscopy,the particle size of the yeast proteins in solution was determined by laser diffraction particle size analyzer,and the secondary structure of the yeast protein was determined by Fourier transform infrared spectroscopy.The results showed that YP-5 contains the highest total mineral content,and the content of each yeast protein varies.The highest vitamin B_(2)content measured in YP-2 was 0.240 mg/100 g.The total content of vitamin PP in YP-3 and YP-4 was not much different.The ratios of EAA(essential amino acids)/TAA(total amino acids)of the five yeast proteins were all above 0.44,and the ratios of EAA/NEAA(Non-essential amino acids)were all above 0.79,which proved that yeast protein is an ideal protein source.The sequence determination of yeast protein free polypeptide showed that the expression of polypeptide was different among all groups.Scanning electron microscope results showed that the yeast protein was aggregated,and the particle diameters were 2.20–4.01μm.The results of laser diffraction particle size analyzer showed that the average particle size of yeast protein solution particles was between 3–5μm.Among them,YP-4 had the largest average particle size.In addition,secondary structures showed that the amide I bands of the five yeast proteins were concentrated at about 1724 cm^(–1).These results can provide theoretical guidance for the development of functional products of yeast proteins.