a and b. The effect of ultrasonic pre-treatment (at various power ratings) on lipase stability in acetonitrile. pH tuned lipase (1 mg) in acetonitrile (100 μl) was ultrasonicated at various power ratings (i.e. 110 W, 66 W and 44 W) continually. In this study, we carried out ultrasonication for 5 minutes, followed by a break of 10 minutes between each cycle. This ensured that the temperature of the sample could be maintained at 40 ± 1°C throughout. The value on the x-axis denotes the total time during which the ultrasonicator was 'on'. Samples were extracted at various intervals (i.e. 1, 2, 3, and 4 h) and an esterase assay was performed using pNPP as a substrate. Note: (a) Burkholderia cepacia lipase and (b) Pseudomonas fluorescens lipase. The experiments were carried out in triplicate. The error bar reflects the reproducibility for each data point.