Analytical methods and stability assessment of liquid yeast derived sucrase

Two independent analytical methods for determining the activity and stabili ty profile of liquid yeast derived sucrase (YS) were established and valida ted in order to conduct preliminary stability studies as a function of temp erature. The methods included a hexokinase-based (HK) enzymatic assay for d etermining the formation of glucose upon hydrolysis of sucrose by YS, and a direct polarimetric procedure to quantitate YS hydrolysis of sucrose. Both assays were validated with respect to YS dilution, incubation time, sucros e or glucose concentration, linearity of response and within- and between-d ay variability. A preliminary stability study was conducted over a 24 week period with liquid YS samples stored at - 20, 4, 30, 40 and 50 degrees C. E nzymatic activity was monitored as a function of time using both the HK and polarimetric assays. Liquid YS samples stored at - 20, 4 and 30 degrees C retained 100% activity after 24 weeks storage, while the samples stored at 40 degrees C lost approximately 70% activity over the same storage period a nd samples stored at 50 degrees C lost approximately 95% activity after 12 weeks storage. The two methods of analysis gave consistent results over the course of the study. (C) 1998 Elsevier Science B.V. All rights reserved.