Factors affecting the heat stability of lipase produced by a strain of Pseudomonas fluorescens

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Abstract

Maximum lipase activity produced during growth of Pseudomonas fluorescens strain 38 at 10°C was approximately fifteen times greater in half strength peptone water than in whole milk. Lipase production in the latter medium at 4°C was approximately 25% greater than at 10°C.

Isoelectric focusing of lipase produced in both UHT whole milk and half strength peptone water gave one band of activity at pH 5·0. Also, both temperature and pH optima for lipase activity were similar for the enzyme produced in either of the two culturing media. The thermostability of lipase at 71·5°C was greater in whole milk cultures than in peptone water cultures. A simulated HTST pasteurization heat treatment (71·5°C for 15 s) caused complete deactivation of lipase in partially purified preparations obtained from both culturing media. However, after the same heat treatment in the presence of either Triton X-100 (0·1% v/v) or casein (3·5% w/v) approximately 65–70% and more than 90%, respectively, of the enzymic activity of partially purified lipases was retained.

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