Efficient Physisorption of Candida Antarctica Lipase B on Polypropylene Beads and Application for Polyester Synthesis

Simone Weinberger,Thomas Farmer,James Comerford,Alessandro Pellis,Georg Guebitz

doi:10.3390/catal8090369

Abstract

In the present work, Candida antarctica lipase B (CaLB) was adsorbed onto polypropylene beads using different reaction conditions, in order to investigate their influence on the immobilization process and the enzyme activity of the preparations in polymerization reactions. In general, lower salt concentrations were more favorable for the binding of enzyme to the carrier. Polymerisation of dimethyl adipate (DMA) and 1,4-butanediol (BDO) was investigated in thin-film systems at 70 °C and at both atmosphere pressure (1000 mbar) and 70 mbar. Conversion rates and molecular masses of the reaction products were compared with reactions catalyzed by CaLB in its commercially available form, known as Novozym 435 (CaLB immobilized on macroporous acrylic resin). The best results according to molecular weight and monomer conversion after 24 h reaction time were obtained with CaLB immobilized in 0.1 M Na2HPO4\NaH2PO4 buffer at pH 8, producing polyesters with 4 kDa at conversion rates of 96% under low pressure conditions. The stability of this preparation was studied in a simulated continuous polymerization process at 70 °C, 70 mbar for 4 h reaction time. The data of this continuous polymerizations show that the preparation produces lower molecular weights at lower conversion rates, but is comparable to the commercial enzyme concerning stability for 10 cycles. However, after 24 h reaction time, using our optimum preparation, higher molecular weight polyesters (4 kDa versus 3.1 kDa) were obtained when compared to Novozym 435.

Highlights

During the last 30 years, issues such as climate change, petroleum depletion and environmental pollution have highlighted the importance of bio-based and environmentally friendly production processes to be adopted across a wide range of industrial fields [1,2]
Novozym ® 435 containing Candida antarctica lipase B immobilized on macroporous acrylic resin, displaying a synthetic activity of 11,700 PLU U g−1 and Lipozyme CaLB were purchased from Sigma-Aldrich (Vienna, Austria)
In polymerization reactions of dimethyl adipate (DMA) and BDO to aliphatic, linear bio-based polyesters that used the thin-film method lead to better results at 70 mbar than at atmosphere pressure, since the byproduct of the reaction has an inhibiting effect on the biocatalyst

Summary

Introduction

During the last 30 years, issues such as climate change, petroleum depletion and environmental pollution have highlighted the importance of bio-based and environmentally friendly production processes to be adopted across a wide range of industrial fields [1,2]. The substitution of highly stable, petrol-based plastics with bio-based and biodegradable products has been, and continues to be, of great interest for public, industry and academia. To address this increasing demand for environmentally friendly polymers, the ability of enzymes to transform natural and non-natural compounds into polymers is considered as a superior alternative to harsh chemical synthetic pathways [3]. Catalysts 2018, 8, 369 they are known as versatile catalysts They are interesting tools for structure-regulated reactions since they combine, in many cases, high enantio-, chemo-, regio-, stereo- and choroselectivity with mild reaction conditions. The development of an effective enzymatic catalyst has great potential for the improvement of industrial chemical processes, while the environmental footprint could be reduced via the use of enzymes since known to be natural catalysts [5]

Methods

Discussion

Conclusion