Application of response surface design to solvent, temperature and lipase selection for optimal monoglyceride production

This work focuses on the use of a temperature and solvent lipase stability procedure as a practical approach for selection of the most favorable conditions for the enzyme catalysis production of monoglycerides from glycerin and triolein. Two lipases were selected for analysis: a lipase from Candida rugosa immobilized on chitosan and a lipase from Mucor miehei immobilized on a macroporous anionic exchange resin of the phenolic type. Using a 32 factorial experimental design, the effects of temperature within the range of 35–45 °C and solvent ratios of acetone:isooctane between 0.25:0.75 and 0.75:0.25 (v/v) were evaluated on the activity of the lipase. Lipase from M. miehei revealed a higher residual activity (91%) following a 24 h incubation with the solvent acetone:isooctane at a ratio of 0.25:0.75 (v/v) at 35 °C while C. rugosa lipase reached a maximum residual activity of approximately 56% after a 24 h incubation with a solvent acetone:isooctane ratio of 0.25:0.75 (v/v) between 35 and 42 °C. For the M. miehei lipase, these results were evaluated experimentally by testing glycerolysis of triolein (biocatalyst initial water activity (aw) 0.534, molar ratio glycerin:triolein 3:1, amount of protein 90 mg, 24 h). Using the best (35 °C, 0.75 Ac) and the worst (45 °C, 0.75 Ac) conditions for residual activity in stability assays, it was confirmed that when the predicted optimum conditions were applied, a monoolein yield of over 68% and a total conversion of triolein of approximately 89% were reached.

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► A temperature/solvent lipase stability method was used to select reaction conditions.
► Mixtures of different log P permit screening of solvent effect on lipase stability.
► The stability of M. miehei lipase was increased rising the acetone concentration.
► The best conditions for M. miehei stability allowed reaching ∼68% of monoolein yield.
► Support aquaphilicity was a key factor for the stability in organic solvents.