Yeast is an important organism for expression of recombinant protein
and DNA in biotechnology research. Protein and DNA released by
mechanical disruption are amenable to degradation due to high shear and
temperature rise in conventional processes. In the present work
cryogenic grinding has been employed for the first time to disrupt
yeast cell by embrittlement at -196 degC, which results in less
denaturation of intracellular protein and DNA. The protein release
process is found to follow first-order protein release kinetics, and is
dependent on the following parameters: volume of suspension, weight of
impactor and rate of grinding. It was possible to release nearly 100%
of soluble protein with protein denaturation of 18%. Our results
suggest that cryogenic grinding enhances protein release rate to almost
1000 fold as compared to ambient condition grinding process. Although
DNA release rate was found to be relatively low as compared to that of
protein, the release was very high, approximately 1 mg DNA per 100 mg
of yeast. High molecular weight DNA strands of 45 kbp were released
with minimum shearing, which is generally difficult to obtain with
other mechanical disruption processes. The results suggest that
cryogenic grinding is a promising technology for release of protein and
DNA.