Production of <FONT FACE=Symbol>a</FONT>-amylase in acid cheese whey culture media with automatic pH control

Abstract

The influence of aeration and automatic pH control on the production of <FONT FACE="Symbol">a</FONT>-amylase by a strain of Bacillus subtilis NRRL 3411 from acid cheese whey was studied. Tests were carried out in a rotary shaker and in mechanically stirred fermenters. <FONT FACE="Symbol">a</FONT>-amylase was analysed according to DUN’s method. Oxygen absorption rate was determined by Cooper’s method. Cell oxygen demand was determined as oxygen consumption in a Warburg respirometer. The level of dissolved oxygen was measured by means of a galvanic silver-lead electrode. Results suggest the possibility of industrial use of acid cheese whey as a carbon source for <FONT FACE="Symbol">a</FONT>-amylase production, since the yield was similar to that produced with lactose. The highest <FONT FACE="Symbol">a</FONT>-amylase levels 10,000 DUN/ml units were not attained at higher aeration rates -431 mLO2/L.h-. The indicated value correspond to a 96 h process with automatic pH control at 7.5. These conditions resulted in double concentration of <FONT FACE="Symbol">a</FONT>-amylase. The enzyme production was directly related to growth in the form of cell aggregates.