7-07: Analytically determining whether to purchase or manufacture a process enzyme

Cubic cost functions (in $/gram) and linear profit functions (also in $/gram) have previously been developed to relate market value to enzyme functionality (in activity/gram).  In this study, an additional square root performance function also describing enzyme functionality (in activity/gram) is developed in order to analytically evaluate how much value is contributed by that enzyme as it converts a substrate chemical to a derivative product.  Enzyme reactions in high solids environments (such as cellulase- cellulose systems) may operate in proportion to the square root of the enzyme concentration/activity in keeping with catalytic  diffusion-reaction models.  The focus of this analysis is the comparison of the respective maximum values added to profit and cost functions. In other words, the optimal difference between the performance function and the profit (here, vendor selling price) function describes the best economic condition for the case in which an enzyme is purchased from an outside source for use in a commercial process. The optimal difference between the performance function and the cost function, similarly, describes the best economic condition for the case in which an enzyme is manufactured in-house for use in the same commercial process.  The comparison between the two situations provides a rationale to determine whether to purchase an enzyme such as cellulase or manufacture it for application to a cellulose to sugar process.