Water-Retaining Polymers in Organic Solvent Increase Lipase Activity for Biodiesel Synthesis

Background: Biocatalyzed esterification reactions in non-aqueous media require water removal materials and optimized enzyme formulations to improve reaction rate and conversion. We have tested a lipase biocatalysis process using anionic polymeric chains of polyacrylate as super-absorbent of water in the conversion of methyl oleate from oleic acid and methanol and in toluene as reaction medium. The water removal material that we used also for the enzyme immobilization is commercially named Aquasorb 3005K2 (herein called Aquasorb).

Methods and findings: The synthesis of methyl oleate was catalyzed by Candida rugosa lipase or lipase G from Penicillium camemberti in the presence or absence of Aquasorb. The simple addition of Aquasorb to the reaction media of the lipase (commercial sample) catalyzed reaction allowed an enzyme activity 20% and 40% higher than that in the absence of Aquasorb for lipase from C. rugosa and lipase G, respectively. Furthermore, for the commercial form of lipase G, when used in the presence of Aquasorb, it was obtained a higher conversion of esterification (93% instead of 60%). Aquasorb was used also as support for the adsorption of the enzyme (via hydrogel formation followed by lyophilization) producing a lipase that was 100% and 60% more active than the enzyme dissolved in buffer in the absence of Aquasorb and lyophilized. However, these lipase formulations showed only about 20 % activity compared to when dry Aquasorb was simply added to the non-aqueous reaction medium.

Conclusions: The use of Aquasorb appears beneficial as additive in esterification reactions (e.g., for biodiesel production) catalyzed by lipases in non-aqueous reaction media.

Author(s): Fiamma Ghisleri, Pengcheng Fu, Francesco Secundo

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