A novel approach for lignin and hexenuronic acid (HexA) removal from cellulosic pulp based on the combination of a vanadium haloperoxidase (Hap) and the tertiary amine 1,4-diazabicyclo[2.2.2]octane (DABCO) as a co-catalyst was tested on oxygen-delignified kraft pulp. It was found that the addition of DABCO, likely through the formation of a reactive quaternary chlorammonium cation, consistently led to an unprecedentedly high lignin removal, HexA reduction and brightness gain in a one-stage enzymatic treatment. Under buffered conditions at pH 4.5 and 60 °C at 10% dry matter, using NaCl as an electron donor and H₂O₂ as an electron acceptor and DABCO as a co-catalyst, high selectivity was achieved, leading to a considerable brightness gain and more than 80% of HexA removal without observing a reduction in the average degree of polymerization of cellulose. The treatment also showed superior HexA removal and selectivity compared to a conventional treatment based on hot acid hydrolysis (A-stage) when applied in a standard bleaching sequence. It was found important to control the pH in the Hap + DABCO stage, as under non-buffered conditions, the performance was inferior when compared to that of a non-enzymatic HOCl treatment. Hydrogen peroxide was proposed to contribute to the brightening during the Hap + DABCO stage.

中文翻译：

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使用卤代过氧化物酶的纤维素造纸纸浆中的酶脱木素和己糖醛酸去除

基于钒卤代过氧化物酶（Hap）和叔胺1，4-二氮杂双环[2.2.2]辛烷（DABCO）作为助催化剂的组合，从纤维素纸浆中去除木质素和己醛糖醛酸（HexA）的新方法是在氧气脱木浆的牛皮纸浆上进行了测试。已发现添加DABCO可能是通过形成反应性季氯铵阳离子，从而在一阶段的酶处理中一致地导致了前所未有的高木质素去除率，HexA降低和亮度增加。在pH 4.5和60°C的缓冲条件下，干物质含量为10％，使用NaCl作为电子供体和H ₂ O ₂作为电子受体和DABCO作为助催化剂，可实现高选择性，从而显着提高亮度，并去除HexA的80％以上，而不会观察到纤维素的平均聚合度降低。与按标准漂白程序进行的基于热酸水解的常规处理（A级）相比，该处理还显示出优异的HexA去除率和选择性。发现在Hap + DABCO阶段控制pH很重要，因为在非缓冲条件下，与非酶促HOCl处理相比，性能较差。有人提出过氧化氢有助于Hap + DABCO阶段的增白。