关键词: 黑曲霉 A．niger 6640, 蔗果低聚糖, β-呋喃果糖苷转移酶, 生物转化

Abstract: In this paper，the preparation conditions of fructooligosaccharides (FOS) via the biotransformation by Aspergillus niger 6640 (A．niger 6640) were optimized，and the properties of crude enzyme of β-Ffase from A． ni-ger 6640 were investigated． Then，β-Ffase was isolated and purified by using an anion column of DEAE Sepharose CL-6B，and its molecular mass was preliminarily measured by means of SDS-PAGE electrophoresis． The results show that (1) the optimal conditions for FOS preparation should be controlled at a pH value of 7． 6，a fermentation time of 40 h，a fermentation temperature of 33 ℃ and a sucrose mass fraction of 40%; (2) in the buffer of Na 2 HPO 4 -citric acid for the biotransformation using vacuum-dried β-Ffase，the optimal conditions are determined as pH 6． 5，a reaction time of 16h and a β-Ffase dosage of 0． 19g; and (3) the molecular mass of β-Ffase after isola-tion and purification is about 75ku．

Key words: Aspergillus niger 6640, fructooligosaccharides, β-fructofuranosidase, biotransformation