Silvia Cesarini

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].

Fast and economic immobilization methods described for non-commercial Pseudomonas lipases

BackgroundThere is an increasing interest to seek new enzyme preparations for the development of new products derived from bioprocesses to obtain alternative bio-based materials. In this context, four non-commercial lipases from Pseudomonas species were prepared, immobilized on different low-cost supports, and examined for potential biotechnological applications.ResultsTo reduce costs of eventual scaling-up, the new lipases were obtained directly from crude cell extracts or from growth culture supernatants, and immobilized by simple adsorption on Accurel EP100, Accurel MP1000 and Celite®545. The enzymes evaluated were LipA and LipC from Pseudomonas sp. 42A2, a thermostable mutant of LipC, and LipI.3 from Pseudomonas CR611, which were produced in either homologous or heterologous hosts. Best immobilization results were obtained on Accurel EP100 for LipA and on Accurel MP1000 for LipC and its thermostable variant. Lip I.3, requiring a refolding step, was poorly immobilized on all supports tested (best results for Accurel MP1000). To test the behavior of immobilized lipases, they were assayed in triolein transesterification, where the best results were observed for lipases immobilized on Accurel MP1000.ConclusionsThe suggested protocol does not require protein purification and uses crude enzymes immobilized by a fast adsorption technique on low-cost supports, which makes the method suitable for an eventual scaling up aimed at biotechnological applications. Therefore, a fast, simple and economic method for lipase preparation and immobilization has been set up. The low price of the supports tested and the simplicity of the procedure, skipping the tedious and expensive purification steps, will contribute to cost reduction in biotechnological lipase-catalyzed processes.

Alternative Oils Tested as Feedstocks for Enzymatic FAMEs Synthesis: Toward a More Sustainable Process

Previously isolated and characterized Pseudomonas lipases were immobilized in a low‐cost MP‐1000 support by a re‐loading procedure that allowed a high activity per weight of support. Immobilized LipA, LipC, and LipCmut lipases, and commercial Novozym® 435 were tested for fatty acid methyl ester (FAMEs) synthesis using conventional and alternative feedstocks. Triolein and degummed soybean oils were used as model substrates, whereas waste cooking oil and M. circinelloides oil were assayed as alternative, low cost feedstocks, whose free fatty acid (FFA), and acylglyceride profile was characterized. The reaction conditions for FAMEs synthesis were initially established using degummed soybean oil, setting up the best water and methanol concentrations for optimum conversion. These conditions were further applied to the alternative feedstocks and the four lipases. The results revealed that Pseudomonas lipases were unable to use the FFAs, displaying a moderate FAMEs synthesis, whereas a 44% FAMEs production was obtained when M. circinelloides oil was used as a substrate in the reaction catalysed by Novozym® 435, used under the conditions established for degummed soybean oil. However, when Novozym® 435 was tested under previously described optimal conditions for this lipase, promising values of 85 and 76% FAMEs synthesis were obtained for waste cooking oil and M. circinelloides oil, respectively, which might result in promising, nonfood, alternative feedstocks for enzymatic biodiesel production.