1.7.1.7	-20°C, 50% glycerol	
1.7.1.7	-70°C, 2 months, less than 20% loss of activity	
1.7.1.7	-70°C, 2-mercaptoethanol, 6 months, less than 15% loss of activity after several rounds of freezing and thawing	
1.7.1.7	-80°C, no loss of activity	
1.7.1.7	-80°C, stable