Acceleration of yeast autolysis by chemical methods for production of intracellular enzymes

Author(s): Breddam K, Beenfeld T

Abstract

Known methods for the acceleration of yeast autolysis have been investigated and new methods have been developed. It is shown that autolysis can be induced by plasmolysis with a number of solvents. The efficiency of this treatment is dependent on the nature of the solvent, its concentration and the duration of the treatment. Plasmolysis generally does not cause release of molecules of high molecular weight (MW) such as enzymes. However, addition of water initiates autolysis and the enzyme carboxypeptidase Y (MW 64000), for example, is released. The rate of this process is very dependent on pH; at the optimal pH (around 8.0) essentially complete autolysis is achieved within 20 h using the best solvents. Control of pH through the process is required. Straight-chain alcohols of medium chain length, i.e. C6–C9 appear to function efficiently in amounts of only 1.2 ml/100 g yeast. In amounts of 2.5–10 ml solvent/100 g yeast trichloroethane, chloroform and in particular ether also provide efficient plasmolysis. Furthermore, it was shown that treatment of an aqueous suspension of yeast cells with a variety of non-ionic as well as ionic detergents caused autolysis. The influence of pH corresponds to that observed with organic solvents, i.e. a pH around 8.0 is optimal. This autolysis process was most efficient when the compressed yeast had been initially plasmolysed by treatment with sodium chloride followed by addition of water. The inexpensive detergents Triton X-100 and N-lauroylsarcosine appeared to be among the most efficient. The methods described in this paper are inexpensive and can be employed on a large scale. In addition, cell debris is easily removed, which is very important for subsequent down-stream processing. In the alternative method using physical breakage by homogenization this step is highly problematic.

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