The present invention relates to a method for separating and purifying a target protein, a method for preparing a target protein, and a method for bioconversion by a whole cell enzyme or a partially purified enzyme. According to the present invention, when the sHSPs are added in cultivation, separation and purification processes for preparing a target protein, the target protein can be obtained at high yields by preventing the loss of protein by proteases. Also, when sIISPs are added in a reaction process using a whole cell enzyme or a partially purified enzyme, the yield of bioconversion using enzyme can be increased by preventing the loss of enzyme by proteases.