Through the use of the software Maple®, the derivative of the above equation was found with the conditions of 67.8% ultrasound power, 1.67 mass ratio buffer solution/oil, and 0.06 mass ratio of catalyst/substrate, yielding 69.50%. The experimental yield result found under the above conditions was 71.50 ± 2.5%, confirming that within the investigated conditions, the model can satisfactorily describe the yield of the hydrolysis reaction.
In Figure 5 are presented the response surface plots for enzymatic hydrolysis yield of the Crambe oil with oil-free seeds as a catalyst. In Figure 5-a , it is observed that the highest yield region is in the highest ultrasound power and buffer solution/oil mass ratio region. When the power effect is evaluated together with the amount of catalyst (Figure 5-b ), the result is different from the seeds in natura. When a higher power was needed for higher values of catalyst ratio, the two variables had little correlation, and a parabolic effect was observed for the catalyst/substrate ratio effect, with the yield reaching a maximum value at a ratio of approximately 0.05. After that, a small drop occurred, indicating that in this range, the substrate is already saturated with the enzyme, and the increase only hinders the reaction by increasing the viscosity of the medium. InFigure 5-c, an interesting effect is observed. The higher the amount of buffer solution added to the reaction, the lower the amount of catalyst required for a good yield. The opposite was also observed, the higher the amount of catalyst, the less amount of solution was necessary. With these results, it is possible to perform a cost analysis to determine the best conditions under particular situations.