Lipase improvement: goals and strategies

Lipases have received great attention as industrial biocatalysts in areas like oils and fats processing, detergents, baking, cheese making, surface cleaning, or fine chemistry [1,2]. They can catalyse reactions of insoluble substrates at the lipid-water interface, preserving their catalytic activity in organic solvents [3]. This makes of lipases powerful tools for catalysing not only hydrolysis, but also various reverse reactions such as esterification, transesterification, aminolysis, or thiotransesterifications in anhydrous organic solvents [4,5]. Moreover, lipases catalyse reactions with high specificity, regio and enantioselectivity, becoming the most used enzymes in synthetic organic chemistry [6]. Therefore, they display important advantages over classical catalysts, as they can catalyse reactions with reduced side products, lowered waste treatment costs, and under mild temperature and pressure conditions [7]. Accordingly, the use of lipases holds a great promise for green and economical process chemistry [8,9]. However, performance of a lipase is not always sufficient for an industrial application [9] and most enzymes have sub-optimal properties for processing conditions [10]. In fact, there are still disproportionally few examples of commercial scale applications of such biocatalysts in the manufacture of fine chemicals. In order to improve enzyme-mediated process efficiency, two different pathways can be followed: i) fitting the process to the available biocatalyst by medium engineering or modification of the manufacturing system to suit the sensitivities of the biocatalyst [11], or ii) obtaining better biocatalysts through different strategies that can be run in parallel [9]. These strategies (Figure 1) include the exploration of biodiversity to expand the sources and number of new biocatalysts, immobilization of existing enzymes, reaction conditions modification [12,13], or the proper modification of these biocatalysts to get the most suitable variant for a defined industrial process [9]. In this case the use of rational protein design to improve enzymes for which the 3D structure has been elucidated or homology-modelled [14], or the use of directed evolution can provide optimal biocatalysts [15].