Specific Enzyme-Catalyzed Hydrolysis and Synthesis in Aqueous and Organic Medium Using Biocatalysts with Lipase Activity
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Specific Enzyme-Catalyzed Hydrolysis and Synthesis in Aqueous and Organic Medium Using Biocatalysts with Lipase Activity from Aspergillus niger MYA 135 Cintia M. Romero • Licia M. Pera Flavia Loto • Mario D. Baigori
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Received: 31 May 2012 / Accepted: 26 August 2012 / Published online: 20 September 2012 Ó Springer Science+Business Media, LLC 2012
Abstract In the present study, the specific hydrolytic activity of three biocatalysts such as the constitutive mycelium-bound lipase, the induced mycelium-bound lipase and the lyophilized induced supernatant from A. niger MYA 135 was evaluated in both aqueous and organic media. A direct correlation between activity in water and n-hexane was not observed for the same hydrolytic reaction. The n-hexane/water activity ratio (RO/A) was applied to characterize the activity in organic medium. The three biocatalysts showed RO/A values higher than 1 for hydrolysis of long-chain fatty acid esters, demonstrating a higher specific hydrolytic activity in organic solvent than in water. A different behavior was observed during hydrolysis of middle-chain fatty acid esters, which was higher in aqueous medium (RO/A \ 1). Transesterifications of different alcohols with various p-nitrophenyl derivatives using all three biocatalysts preparations were also evaluated in nhexane. For methanolysis and ethanolysis, the constitutive mycelium-bound lipase displayed an interesting preference for C16 substrate (p-nitrophenyl palmitate). The induced mycelium-bound lipase showed high specific transesterification activities in the presence of water-miscible alcohols and middle-chain fatty acid esters (p-nitrophenyl caprate and p-nitrophenyl laurate), being the highest specific transesterification activity (91.4 ± 1.7 mU/gdw) observed in a reaction mixture containing propanol and p-nitrophenyl laurate. Finally, both p-nitrophenyl caprate (C10) and p-nitrophenyl laurate (C12) were preferentially methanolized by the
C. M. Romero L. M. Pera F. Loto M. D. Baigori (&) Planta Piloto de Procesos Industriales Microbiolo´gicos (PROIMI)-CONICET, Av. Belgrano y Pasaje Caseros, 4000 Tucuma´n, Argentina e-mail: [email protected]
lyophilized induced supernatant, being this lipase activity the most specific biocatalyst preparation under transesterification conditions. A selectivity-based analysis of each lipase preparation toward transesterification or hydrolysis in organic medium was evaluated as well. Keywords Lipase Aspergillus niger Hydrolysis Transesterification Organic medium Aqueous medium Substrate specificity
1 Introduction Among all the enzymes that show significant activity in organic media, lipases are of particular interest because of their commercial potential in many applications [1, 2]. Lipases have been widely used as common reagents for ester hydrolysis and synthesis, and lipase-catalyzed reactions are often carried out in organic solvents [3]. However, organic solvents frequently alter enzymatic activity, enzyme stability and substrate specificity [4]. Observations in the three-dim
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