Abstract: A mutant fungus strain which produces a protease with low thermostability and low productivity was made from protease producing fungi and the gene coding for mutant enzyme is isolated from the mutant strain. A promoter which can function in yeast is ligated to the gene and inserted into a plasmid replicable in yeast, and the resulting plasmid is introduced into yeast. The yeast is cultured, thereby producing the mutant enzyme. Furthermore, a gene expressing an enzyme with a far lower thermostability is prepared by site-directed mutagenesis, which is introduced in yeast, thereby producing an enzyme with more distinctively reduced thermostability.

Abstract: Disclosed is a process for the interesterification of oil or fat by treating such oil or fat in presence of a fatty acid or fatty acid ester or different oil or fat wherein a reactor column that is packed with an alkaline high molecular weight lipase preparation containing 0 to 5% moisture is fed with a substrate solution composed of the above oil or fat and fatty acid or fatty acid ester or different oil or fat for a continuous reaction in such a manner that the substrate solution contains 100 to 1800 ppm moisture and 50 to 800 ppm moisture at the inlet and outlet, respectively, of the column.

Abstract: A method for increasing the milk coagulating activity of microbial rennet obtained from Mucor pusillus microorganisms, which comprises acylating the microbial rennet in an aqueous medium by contacting the microbial rennet with succinic anhydride at a temperature of about 0.degree. C. to about 40.degree. C. and a pH of about 4 to about 10 for a time sufficient to obtain the desired increase in milk coagulating activity; and improved microbial rennet having a low PA/MCA index and a high MCA index and obtained by the aforesaid method.

Abstract: A microbial lipase which has (i) an optimal pH for activity of about 9.+-.0.5, (ii) an optimal temperature for activity of about 40.degree. C. to about 48.degree. C., (iii) a lipase activity to be activated by bile salts, (iv) a cholesterol esterase activity, and (v) a molecular weight of about 30.times.10.sup.4 to about 40.times.10.sup.4 ; a process for its preparation; and microbiologically pure culture therefor.

Abstract: A process for improving the quality of microbial rennet by inactivating cellulase impurities in microbial rennet which comprises heat-treating microbial rennet in an aqueous medium in the presence of sodium chloride.