LAUSR

Abstract This study evaluated coupled effects of molar ratio of substrates and enzyme loading in a solvent-free system using a simple mathematical approach to obtain high conversions on octyl caprylate synthesis with Novozym 435. When molar ratios of caprylic acid to n-octanol (1:1 and 1:3) were evaluated with enzyme loadings of 1% to 4% (wt/wt acid), an interdependence between the masses of reagents and the enzymes was observed, that was expressed as a mathematical relation. The study of this relation, named as SER, indicated a specific range of reaction conditions that resulted in conversions above 90%. The most suitable condition corresponded to an acid:alcohol molar ratio of 1:1.3 and an enzyme loading of 1.5%, resulting in 94.5% of conversion at 65 °C in 3 hours of reaction. A different reaction system (bottle reactor) was used to evaluate the influence of reagents mixture and heat distribution. The use of a bottle reactor allowed yield improvement that reached 99.3%. At this condition, Novozym 435 was reused, without washing steps, in three subsequent batches keeping high conversion. A possible balance between the shift of chemical equilibrium by stoichiometric excess of reagents and enzymatic inhibition effects by substrates can be expressed mathematically in a convenient way, helping to predict the behaviour of synthesis in different conditions. The mathematical relation proposed, SER, allowed the achievement of 99% of conversion on enzymatic synthesis of octyl caprylate.