生物塑料聚(己二酸丁二酸二丁酯-2,5-呋喃二羧酸丁二醇酯)前体的酶催化合成

Enzyme-catalyzed synthesis of precursor of the bioplastic poly(butylene adipate-co-butylene 2,5-furandicarboxylate)

摘要:

【目的】 聚(己二酸丁二酸二丁酯-2,5-呋喃二羧酸丁二醇酯) [poly(butylene adipate-co-butylene 2,5-furandicarboxylate), PBAF]是一种可生物降解的呋喃基共聚酯塑料。化学合成PBAF的过程中，寡聚片段聚合的随机性会生成嵌段共聚物、无规共聚物、交替共聚物等多种复杂聚合物，从而影响生物塑料PBAF的质量。本研究以单体2,5-呋喃二甲酸二甲酯(dimethyl furan-2,5-dicarboxylate, FDME)和1,4-丁二醇(1,4-butanediol, BDO)为底物，通过酶促反应合成双(4-羟基丁基)呋喃-2,5-二羧酸酯(bis-BDO ester)，为生物塑料PBAF提供可以进行可控聚合反应的生物塑料前体，从而减少副产物生成的问题。【方法】 在大肠杆菌(Escherichia coli) BL21(DE3)中异源表达来源于嗜橡胶根瘤杆菌(Rhizobacter gummiphilus)的RgPETase，发现RgPETase对底物FDME和BDO具有一定的酰基转移酶活性。深入研究了合成双(4-羟基丁基)呋喃-2,5-二羧酸酯的反应条件的优化，包括反应pH、反应温度、底物兼溶剂BDO的含量和反应酶量。【结果】 RgPETase的最适反应pH值为8.0，底物兼溶剂BDO的最适含量为30%，最适反应温度区间为25−30 ℃。在最适条件下，即反应温度为30 ℃且酶浓度为6 µmol/L时，RgPETase催化10 mmol/L FDME可产生(2.96±0.01) mmol/L双(4-羟基丁基)呋喃-2,5-二羧酸酯。【结论】 RgPETase具有较好的酰基转移酶活性，能通过酰基转移反应有效催化FDME生成双(4-羟基丁基)呋喃-2,5-二羧酸酯，为生物塑料PBAF前体的合成提供了一条绿色可持续的途径。

Abstract:

[Objective] Poly(butylene adipate-co-butylene 2,5-furandicarboxylate) (PBAF) is a biodegradable furan-based copolyester plastic. In the chemical synthesis of PBAF, the randomness of oligomer polymerization leads to the formation of complex polymers, such as block copolymers, random copolymers, and alternating copolymers. In this study, dimethyl furan-2,5-dicarboxylate (FDME) and 1,4-butanediol (BDO) were used as substrates to synthesize bis-BDO ester by enzymatic reaction to provide the bioplastic precursor for controllable polymerization and avoid complex by-products. [Methods] RgPETase from Rhizobacter gummiphilus was heterogeneously expressed in Escherichia coli BL21(DE3). RgPETase exhibited acyltransferase activity for FDME and BDO. The reaction conditions including pH, temperature, content of BDO (as both substrate and solvent), and amount of enzyme for the synthesis of bis-BDO ester were optimized. [Results] The optimum reaction conditions of RgPETase were pH 8.0, BDO content of 30%, and reaction temperature within the range of 25–30 ℃. Under the optimum conditions (30 ℃ and enzyme concentration of 6 μmol/L), RgPETase can catalyze 10 mmol/L FDME to produce (2.96±0.01) mmol/L bis-BDO ester. [Conclusion] RgPETase exhibits high acyltransferase activity and catalyzes the generation of bis-BDO ester from FDME via acyl transfer reaction under mild conditions, which provides a green and sustainable approach for synthesizing the precursor of PBAF.