A THERMOPHILIC, LIPOLYTIC BACILLUS SP, AND CONTINUOUS ASSAY OF ITS P-NITROPHENYL-PALMITATE ESTERASE-ACTIVITY

The newly-isolated extremely thermophilic Bacillus sp. strain Wai28A5, able to grow at 70 degrees C on tripalmitin and other triglycerides, possessed a p-nitrophenyl-palmitate esterase activity with a half-life of 60 min at 70 degrees C and 12 min at 85 degrees C. This activity w as produced during exponential growth on tripalmitin, and the level of activity decreased once growth stopped. Transfer to tripalmitin-conta ining medium resulted in induction of the esterase activity. The activ ity was largely cell-associated (60 to 87% of the total activity). The p-nitrophenyl-palmitate esterase activity was proportional to the amo unt of culture added to enzyme assays and was destroyed by autoclaving , showing it to be enzymatic. A continuous assay for esterase activity was developed, and proved to be sensitive enough to detect 0.02 mU ml (-1) esterase activity. Maximal esterase activity was at 400 mu M p-ni trophenyl-palmitate and the optimum pH (at 70 degrees C) was 8.7.