Microbial degradation of ether bonds between carbohydrates and residual lignin from kraft pulp

通过纤维素酶/木聚糖酶生物反应器和硅胶柱层析，从未漂白的阔叶木硫酸盐浆(UKP)中分离出了木聚糖酶抗性的水溶性木聚糖组分(LF-D)。化学和光谱分析表明，LF-D中含有大量不可移除的无机原子，包括Si、Na和S，以及未支化的β-1，4-连接木聚糖链。在LF-D的硝基苯氧化反应中，可能存在大量的类Qunid结构。此外，还发现在硫酸盐法制浆过程中，LF-D中的木素发生了脱甲基化。另一方面，相对分子质量较高的残留物(HF-P)含有较多的二苯基甲烷(DPM)结构。土壤细菌菌群对LF-D的脱色效果优于白腐菌。然而，在所测试的白腐菌中，杂色假单胞菌对变色木聚糖组分和完整的UKP本身都有脱色作用。在这两种情况下，都没有检测到木质素过氧化物酶、锰过氧化物酶、漆酶和木聚糖酶的活性。虽然黄孢霉的一株纯化的LIP(H8)氧化了p-乙基化的β-O-4LCC模型，但在反应混合物中没有检测到碳水化合物的部分。因此，利用一种荧光敏感的苄基醚模型化合物进行了对醚化的苄基醚键的定量裂解微生物的筛选。结果，我们分离到了几个发光细菌的单菌落。对这些微生物的进一步研究将有助于开发一种环境安全的纸浆生物漂白系统。

A water-soluble xylanase-resitant chromophoric xylan fraction (LF-D) was separated from a hard wood unbleached kraft pulp (UKP) by a cellulase/xylanase bioreactor and silica gel column chromatography. Chemical and spectroscopic analyzes revealed that LF-D contained a large amount of unremovable inorganic atoms including Si, Na and S,together with non-branched beta-1,4-linked xylan chain. In a nitrobenzen oxidation of LF-D,existence of a large amount of qunoid structure was suggested. In adittion, it was found that lignin in LF-D had been demethylated during the course of kraft pulping. On the other hand, a higher molecular weight residual fraction (HF-P) was found to contain much diphenylmethane (DPM) structure. LF-D was more effectively decolorized by bacterial microflora from soil rather than selected white rot fung. However, C.versocolor was found to decolorize both the chromophric xylan fraction and intact UKP itself among the white-rot fungi tested. In both cases, activities of lignin peroxidase, Mn-peroxidase, laccase and xylanase were not detected during the hole time of cultivation.Although a purified LiP (H8) from P.chrysosporium wa oxidized a p-ethylated beta-O-4LCC model, carbohydrate moiety was not detected in the reaction mixture. Therefore, screening of microorganisms which quantitatively cleave p-etherified benzyl ether bonds was carried out using a fluorescence-sensitive benzyl ether model compound. As a result, several bacterial single colonies which emit fluorescence were isolated. Further study on the characterization of these microorgansims would lead to an environmentally safe biobleaching system of pulps.