본 연구에서는 천연리그닌의 전구물질인 3종의 모노리그놀[p-coumaryl alcohol (PCA), coniferyl alcohol(CA), sinapyl alcohol (SA)]을 이용하여 horseradish peroxidase (HRP, EC. 1.11.1.7)/$H_2O_2$ 조건하에서 dehydrogenative polymers (DHPs)를 제조하였다. 합성한 DHPs와 천연리그닌의 구조적 특성을 비교하기 위해 소나무와 포플라 milled wood lignin (MWL)과 함께 Gel permeation chromatography (GPC)에 의한 분자량 측정과 Derivatization followed by reductive cleavage (DFRC) 분석에 의한 ${eta}$-O-4 결합 빈도를 측정하였다. DHP 합성 수율은 CA만을 단독으로 주입한 G-DHP가 71%로 가장 높았고 PCA에 의한 H-DHP 수율은 42%로 나타났다. 그러나 horseradish peroxidase/$H_2O_2$ 조건하에서 SA 단독으로는 S-DHP는 전혀 합성되지 않았다. 합성한 DHPs의 분자량(Mw)은 3,000~4,700 범위로 측정되었는데, 이는 침엽수 리그닌인 소나무 MWL (G-type lignin: Mw 7340)의 절반 정도였고 활엽수인 포플라 MWL (GS-type lignin: Mw 13,250)의 1/3 수준으로 측정되었다. DHP 합성 과정에서 형성된 ${eta}$-O-4 결합 빈도는 GS-DHP가 502 ${mu}mol$/g으로 가장 높았지만 포플라 MWL (1107 ${mu}mol$/g)의 1/2 수준에 머물렀고, G-DHP의 경우도 약 286 ${mu}mol$/g으로 H-DHP (127 ${mu}mol$/g)보다 약 2.5배 이상 많은 ${eta}$-O-4 결합을 형성하였지만 소나무 MWL (651 ${mu}mol$/g)과 비교하여 절반 정도로 측정되었다.
In this study diverse dehydrogenative polymers (DHPs) were synthesized with three precursors of native lignin [p-coumaryl alcohol (PCA), coniferyl alcohol (CA), sinapyl alcohol (SA)] in the presence of horseradish peroxidase (HRP, EC. 1.11.1.7)/$H_2O_2$. To compare the structural features between DHPs and native lignin, the DHPs as well as pine/poplar milled wood lignins were simultaneously subjected to gel permeation chromatography (GPC) to determine average molecular weights and derivatization followed by reductive cleavage (DFRC) to investigate the frequency of ${eta}$-O-4 linkage. The highest yield of DHP was measured to 71% when CA was solely injected (G-DHP) and the yield of H-DHP was 42%. However, single injection of SA could not form any polymer in this system. The average molecular weights of DHPs were ranged between 3,000~4,700, which were only 1/2 fold compared with that of pine MWL (G-type lignin: Mw 7,340) and 1/3 scale compared with that of poplar MWL (GS-type lignin: Mw 13,250). DFRC analysis revealed that the formation of ${eta}$-O-4 linkage during dehydrogenative polymerization was the highest in the GS-DHP with ca. 502 ${mu}mol$/g, which was, however, remained to only 50% compared to that in poplar MWL (1107 ${mu}mol$/g). The ${eta}$-O-4 linkage was estimated to ca. 286 ${mu}mol$/g In the G-DHP, which was twice as much as that of H-DHP(127 ${mu}mol$/g). Similar to GS-DHP, only half amount of ${eta}$-O-4 linkage, compared to pine MWL, was formed during in vitro polymerization of CA by horseradish peroxidase/$H_2O_2$.
