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A plasmid pTTY;containing the lipase-producing gene, was used to transform an E. colt phage lysogen, P90c/￠434, into the lipase-producing lysogen, P90c/0434/pTTY2. After the overproduction of lipase by the isopropylthio-/9-D-galactoside induction, the prophage 0434 in the chromosome of the host cell was induced by the mitomycin C addition or ultraviolet irradiation to lyse the host cell. The optimum operating conditions, such as the isopropylthio-R-D-galactoside induction period and the phage induction timing, were sought for the efficient cell lysis in the same fermenter. Effective cell lysis occurred at the earlier exponential growth phase with the isopropylthio-8-D-galactoside induction period of 1 hour. The amount of the lipase production was qualitatively measured by the halo size in LuriaBertani agar medium containing tributyrin and Rhodamine B plate.
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