Abstract

EFFECT OF FREEZING ON INVERTASE ACTIVITY OF SACCHAROMYCES CEREVISIAE CELL

Michele Vitolo*

Abstract

Freezing is a process largely used in conservation of biological material (foods, tissues, biomolecules etc.). Before freezing, the material is dissolved (if soluble) or suspended (if insoluble, as yeast cells) in buffer at definite pH and concentration. We studied the effect of buffer composition and pH (4.0 – 9.0) on yeast cell invertase activity (YCIA) during freezing at cooling rates of 5 oC/min (rapid freezing; RF), 1.5 oC/min (slow freezing; SF), and 33 oC/min (very slow freezing; VSF). Buffer composition and pH significantly affected YCIA. Cell suspension in succinate buffer (pH 4.0 and 4.6) accounted for the highest activity, stability, and resistance under freezing – thawing. The use of cryoprotectants such as glycerol and ethylene glycol was effective for avoiding YCIA loss when the yeast suspension was subjected to freezing-thawing.

Keywords: Yeast, invertase, freezing, Saccharomyces cerevisiae.