酯化前后酵母菌的红外光谱比较

对啤酒酵母酯化前后的红外光谱进行了分析。啤酒酵母的红外光谱图主要由蛋白质的吸收带、碳水化合物的吸收带组成。1 652 cm-1处的吸收峰为酰胺Ⅰ带，是CO的伸缩振动，1 542 cm-1的吸收峰是酰胺Ⅱ带，振sup>振动和N—H的弯曲振动引起的。1 454 cm-1处的吸收峰为CH₃和CH₂的弯曲振动峰;1 160 cm-1处出现的峰可能为细胞壁的主要成分——碳水化合物中C—O的伸缩振动峰;1 080 cm-1处的吸收峰是由啤酒酵母中的RNA，DNA或细胞壁中存在的碳水化合物或醇中的C—O伸缩振动引起的。用甲醇酯化后在1 744和1 454 cm-1处的吸收峰强度增加，说明酵母菌细胞表面的羧基发生了酯化反应。酯化后细胞的主要成分和结构保持完整。

Comparison of Infrared Spectra of Native and Esterified Beer Yeast

The native beer yeast and esterified beer yeast were examined by infrared spectroscopy. The IR spectrum of beer yeast is mainly composed of the adsorption of carbohydrates, protein, etc. The dominating bands near 1652, 1532 and 1240 cm(-1) were assigned to amide I, amide II and amide III, and the characteristic IR absorption of protein could be one of the significant components of cell walls. The peak near 1 454 cm(-1) is attributable to the bending stretching of CH2- and CH3-. A substantial portion of the absorbance at 1160 cm(-1) is attributable to the stretching vibration of C-O on the structure of carbohydrates, the main components of the cell walls. The band present at 1080 cm(-1) was caused by the C-O stretching of carbohydrates and alcohols found in the RNA, the DNA and/or the cell envelop of the yeast. The peaks at 1744 cm(-1) (attributed to the carboxylate stretching) and 1454 cm(-1) confirmed the esterification process of carboxylate groups presented in the cell wall. After esterification with methanol-chloride hydride, the major components and the structures of the biomaterial remained intact.