果胶酸类物质的酶解及其对DCS稳定性的影响

Enzymatic Hydrolysis of Pectic Substances and its Effect on the Stability of DCS from Mason Pine BCTMP

选用两种商品果胶酶制剂,首先优化其酶解果胶类物质的反应条件,结果发现,两种果胶酶在pH值9.0,温度为60～70℃的较优条件下可以有效地酶解果胶类物质和马尾松化学机械浆DCS,降低其阳离子需求量(CD值)。在探求两种果胶酶酶解果胶类物质的机理时,得出在对PGA类物质(酸性果胶物质)进行果胶酸(盐)裂解酶(PGL)处理以降低CD值时,没有必要将其完全酶解成单体,而只需将其聚合度降为6左右即可。碱性果胶酶(PL)处理果胶时也有类似的结果。同时发现,在漂白浆DCS中的果胶类物质主要是以果胶酸的形式存在,在选用果胶酶时应选用PGL。马尾松化学机械浆DCS经PGL酶处理以后虽然对提高DCS的稳定性作用不大,但可以减缓其沉淀的速度。

The efficiency and mechanism of two pectinases degrade or hydrolyze model substances and DCS from Masson pine BCTMP were evaluated. The optimal conditions for pectate lyase （PGL） and alkaline pectinase （PL） treatment were as follows：pH 9.0,60℃,120min for PGL,and pH 9.0,70℃,120 min for PL. Both pectinase could effectively degrade the pectics in the DCS of Masson pine BCTMP,with PGL being more efficient,due to the unmethylated form of pectic substances in DCS of BCTMP. The hydrolysis mechanism of PGA with PGL was investigated. The results showed that it was not necessary to hydrolyze the polymeric pectics to be monomers,in order to reduce its cationic demand,instead it was hydrolyzed to a average DP of 6 would be acceptable. Treatment of DCS from Masson pine BCTMP with PGL could not prevent DCS from complete aggregation by calcium ions,but the rate of aggregation was lowered.