【作者】 张勇；

【导师】 蒲俊文； 谢响明； 吴玉英；

【作者基本信息】 北京林业大学 ， 林产化学加工工程， 2008， 博士

【摘要】 本论文围绕绿色糖单孢菌复合胞外酶生物漂白纸浆这个核心,主要从菌种的活化培养,母液及粗酶液的制备及浓缩,最佳诱导产酶培养基的筛选,所产胞外酶活性和蛋白含量的时程分析等方面就绿色糖单孢菌的最佳发酵条件及产胞外酶的变化规律进行了探索;从菌落和菌丝的形态学观察,胞外酶的耐碱性和热稳定性分析,胞外酶活性及其中木聚糖酶分子量的测定等方面就复合胞外酶的酶学特性进行了表征;从生物漂白的酶用量、pH值、温度、时间和浆浓等因素分析,摸索出了复合胞外酶漂白纸浆的最佳工艺条件;从漂后纸浆的白度提高、后续可漂性改善、物理性能变化及终漂废水污染等几个方面,评定了复合胞外酶漂白纸浆效果;从复合胞外酶与几种常用商品酶及人工复配酶漂后纸浆性能的比较分析,讨论了将其应用于纸浆生物漂白所具备的优势和潜力;利用扫描电镜、气相色谱、X射线衍射、红外光谱及核磁共振等仪器分析手段,阐明了复合胞外酶漂白对纸浆中半纤维素、木素、LCC及纤维素的作用方式和机理。进行了绿色糖单孢菌发酵条件和产酶规律探索,结果表明,松木粉+棉纱培养基为最佳诱导绿色糖单孢菌产木聚糖酶培养基;所产胞外酶中几乎不含纤维素酶,而产木聚糖酶的规律和总蛋白量的时程基本一致;产酶培养156h为绿色糖单孢菌胞外酶的最佳取样点。进行了绿色糖单孢菌胞外酶酶学特性表征,结果表明,绿色糖单孢菌胞外酶中同时含有木聚糖酶、木素过氧化物酶和纤维素酶;与真菌及某些细菌胞外酶相比,胞外酶具有较好的耐碱性和热稳定性,酶学特性符合纸浆漂白工艺中碱性高温环境的要求;其中木聚糖酶的分子量在31KD左右进行了绿色糖单孢菌复合胞外酶漂白纸浆效果评定,结果表明,其最佳纸浆漂白工艺条件为:酶用量30U/g(以木聚糖酶计),反应pH值7,反应温度80℃,漂白时间120min,纸浆浓度10%,环境H2O2含量0.1mmol/L;复合胞外酶漂白不仅可以直接提升纸浆白度,更重要是能够断裂部分木素或与木素相连的化学键,以改善纸浆的可漂性,使纸浆在后续化学漂段中更易脱除残余木素,从而使漂白过程更易进行;在后续化学漂白过程中具有提升纸浆终漂白度和减少后续化学漂剂用量的双重作用;在达到相近终漂白度情况下,可以大幅减少后续漂段的化学药品用量,其漂白废水中化学及生物耗氧负荷远低于传统漂白方法,从而大大减轻化学漂剂对环境所造成的污染。进行了生物酶漂白纸浆效果对照分析,结果表明,绿色糖单孢菌复合胞外酶漂白纸浆,不仅漂白效果优于单纯商品酶,与人工复配酶相当,而且由于其自身具备的耐热嗜碱性能,较普通商品酶可大幅降低纸浆漂白工段能耗。进行了绿色糖单孢菌复合胞外酶作用于半纤维素机理研究,结果表明,复合胞外酶漂白使纸浆中的木聚糖和LCC被大量降解,纤维表面的剥落,出现局部裂隙和大面积的沟槽结构,纤维结构变得疏松,内部木素结构充分暴露出来,有利于增强后续漂白中漂剂的渗透,改善化学漂白的脱木素效果;主要作用于纸浆中的木聚糖和聚阿拉伯糖,对纤维素也有少量破坏,对聚甘露糖不存在降解作用。进行了绿色糖单孢菌复合胞外酶脱木素机理研究,结果表明,复合胞外酶漂白不仅对纸浆中的木聚糖结构有降解作用,同时还可断裂部分残余木素和LCC,减少了纸浆中的发色基团和助色基团,同时可促进木素的溶出。进行了绿色糖单孢菌复合胞外酶作用于LCC及纤维素机理研究,结果表明,复合胞外酶漂白与纸浆LCC的某些结构存在反应;对纸浆纤维素产生一定的破坏作用,且主要集中在纤维素的无定型区,对结晶区的影响较小。本论文的研究属于交叉学科类研究课题,有重要的环境意义和潜在的应用前景。更多还原

【Abstract】 In this study, the effect and mechanism of compound enzyme from Saccharomonospora viridis bleaching pulps was researched. Works mainly included that exploring the best ferment conditions and the rule of producing enzymes, characterizing the enzymology characteristic of compound enzyme, fishing out the best technics of compound enzyme bleaching pulps, assessing the effect of compound enzyme bleaching pulps, discussing the advantages and potentials of compound enzyme bleaching pulps and explaining the process and mechanism of compound enzyme affecting the hemicellulose, lignin, LCC and cellulose in pulps.The results of exploring the best ferment conditions and the rule of producing enzymes showed that deal powder + cotton yarn compoud substrate was the optimal enzyme-induction medium, there was little cellulase in the compound enzyme, the courses of producing xylanase and albumen were almost consistent. 156h was the optimal sampling time.The results of characterizing the enzymology characteristic of compound enzyme showed that Saccharomonospora viridis might be taken as a gene bank for screening alkali-tolerant thermostable xylanase and lignin peroxidase which produced both xylanase and lignin peroxidase at the same time and the compound enzyme was maximally active at pH 7 and retained 63.55 % activity at 90℃for 3h, the molecular weight of xylanase in compound enzyme was about 31 KD.The results of fishing out the best technics of compound enzyme bleaching pulps and assessing the effect of compound enzyme bleaching pulps showed that the best technics of compound enzyme bleaching pulps were enzyme dosage 30U/g (calculated by xylanase), pH 7, temperature 80℃, time 120min, pulp consistency 10%, H2O2 0.1mmol/L, enzymatic treatment with the compound enzyme had beneficial effects on bleachability of pulp and the direct brightening, removal of xylan, lignin and LCC were already observed on the stage of enzymatic treatment and led to increase in ISO brightness and decrease in pentosan, lignin and LCC contents, the brightness improvement under equal or reduced consumption of active bleaching chemicals was all noted after the subsequent bleaching.The results of discussing the advantages and potentials of compound enzyme bleaching pulps showed that the effects of compound enzyme bleaching pulps were prior to all the pure commercial enzymes and almost equivalent to the manual mixing enzymes, because of its thermostability and alkali-tolerance, compound enzyme bleaching pulps could reduce the consumption of energy in pulp bleaching process.The results of explaining the process and mechanism of compound enzyme affecting the hemicellulose, lignin, LCC and cellulose in pulps showed that compoud enzyme treatment degraded xylans and poly-arabinose evidently, it dissolved small molecular lignin and LCC, reduced chromophores and auxochromes in pulp, enzymatic treatment also loosened fibre structure, thus strengthened the infiltration of chemicals in subsequent bleaching and promoted the dissolution of remnant lignin, crystallinity of enzymatic treatment pulp was enhanced.This study is concerned with an interdiscipline research subject. The results are benificial to environment protection and have potential prospect of application.更多还原