Changes in protein composition ofSaccharomyces brewing strains in response to heat shock and ethanol stress

Heat shock on Saccharomyces cerevisiae inoculum increases glycerol production in wine fermentation

A heat shock was applied to Saccharomyces cerevisiae: a change from 18 degrees C to 45 degrees C over 5 min and then maintenance at later temperature for 20 min followed by cooling to 18 degrees C. Such a treated inoculum, when used in an alcoholic fermentation of Welsch Riesling grape must at 18 degrees C, gave up to 12 g glycerol l(-1 )This is a new and easy method for high glycerol production in large scale wine production.

Influence of heat shock on glycerol production in alcohol fermentation

The influence of single and double heat shocks induced during the exponential growth phase of the Saccharomyces cerevisiae fermentation of cultivar Sauvignon Blanc grape must was examined. Rapid temperature changes from 18 degrees C to 34 degrees C have been applied. The effect of the duration of exposure to a high temperature has been analyzed. By the applications of a single heat shock and a double heat shock, up to 8.2 g l(-1) and 11.0 g l(-1) glycerol have been produced, respectively. To prevent the evaporation of fine wine bouquet compounds during the temperature changes, reflux coolers on the top of bioreactors have been employed. By using this method, glycerol production was increased by up to 65%.

Cloning, sequencing and expression of stress genes from the ethanol-producing bacterium Zymomonas mobilis: the groESL operon

Zymomonas mobilis is unique among bacteria in its ability to produce high levels of ethanol (EtOH) during fermentation. Elevated EtOH concentration, like elevated temperature, is a microbial stress and a universal inducer of stress proteins. For Z. mobilis, exposure to high levels of EtOH represents a natural stress. By using a simple strategy which combines the genetic tools of Escherichia coli and Bacillus subtilis, we have cloned genes encoding two of the most abundant stress proteins in Z. mobilis, GroES and GroEL. Both genes were expressed at high levels in E. coli. Despite the unique environment (EtOH concentrations of above 10%) in which the translated products from these genes function in Z. mobilis, the amino-acid sequences encoded were remarkably similar to their homologues from bacteria which are not known to accumulate EtOH. Two small regions were observed, however, which appear more similar to Saccharomyces cerevisiae hsp60 (groEL homologue) than to E. coli or the concensus. These may be related to EtOH tolerance.