|概要||Typically, for production of high brightness pulp, the residual lignin in unbleached kraft pulp is commonly removed through a multi-stage bleaching process with the use of chlorine species. The efflue...nt from such a bleaching process is dark brown due to their content of chromophoric and polymeric lignin derivaties. Moreover, the organically bound chlorine [measured as total organically bound chlorine (TOCI) or adsorbable organic halogen (AOX)] is present in a wide range of organic materials which have toxic and mutagenic properties. It has recently been discovered that small quantities of dioxines [polychlorinated dibenzo dioxin (PCDD) and polychlorinated dibenzo furan (PCDF)] can also appear in bleach plant effluents. Consequently, this bleaching effluent is not easily recycled within a mill recovery system because of the potential corrosion problems created by its high chlorine content and finally affects the harmful effects on the environment. The purpose of the present research is to describe the decolorization of the E_1 effluent with white-rot fungi showing the ligninolytic activity, to accomplish efficient treatment of kraft bleachery efficient with less energy and in relatively short treatment-period. First, it was attempted to design the effective treatment process of the E_1 effluent with the fungus IZU-154 showing ligninolytic activity. It has revealed that the color of the effluent was effectively removed when glucose was added as an additive. Furthermore, the addition of glucono-$ delta $-lactone to the E_1 effluent produced a more remarkable degree of decolorization than did that of glucose. All white-rot fungi tested showed high decolorization effect of the E_1 effluent in the presence of glucono-$ delta $-lactone. It is suggested that the effect of glucono-$ delta $-lactone on the high decolorization of E_1 effluent are closely associated with the activity of the surfaces of the mycelium due to the change of pH of the effluent during fungal treatment. Moreover, to establish a more practical system for the decolorization of the bleaching effluent, a screening have been performed to find fungi having high decolorization activity of the E_1 effluent without any additional nutrients. The strains which had the activity of decolorization were isolated from 1,212 samples of rotted wood of forest habitats. Among the isolated fungi, the fungus KS-62 showed the most effective decolorization of the E_1 effluent and degraded the chlorinated lignin in the E_1 effluent without any additional nutrients. Moreover, the treatment with KS-62 significantly reduced the COD and AOX and decreased the high molecular weight of chlorolignins in the E_1 effluent. To obtain a reasonable basis for the evaluation of an industrial fungal treatment, we have performed the treatment of the E_1 effluent with the immobilized mycelium of the fungus KS-62. The fungal biomass of KS-62 could be maintained for a long-term (at least 40 days) without any appreciable loss of activity in the presence of a critical amount (between 0.050% and 0.075%) of glucose. The COD of the E_1 effluent treated with KS-62 was lower than that of initial E_1 effluent in whole treatment period, which indicated that the fungus KS-62 decomposed the chlorolignin in the E_1 effluent. Based on these experiments, it has become apparent that the biological decolorization of bleaching effluents has been enabled with the lignin-degrading fungi.
上質紙の材料となるクラフトパルプには難漂白性のリグニンが残留するため,塩素系の薬品による多段漂白が必要である.この漂白廃液は強く着色しており,また微量ながらダイオキシン類を含むことが明かとなったが,塩素イオンを含むことから回収処理が困難であり,環境汚染源の一つとして問題となっている.本研究は,リグニン分解能を有する白色腐朽菌による漂白廃液処理の効果とその機構を明らかにし,実用化への指針を示したものである.まず,強力なリグニン分解能を有するIZU-154株を用いて,効果的な廃液処理プロセスの設定を試み,添加剤として糖類の共存下,ほぼ完全な廃液の脱色が可能であることを明らかにした.添加剤としては,グルコノ-$ delta $-ラクトンが最も効果的であり,その効果はリグニン分解菌に共通して認められることを示し,その機構は処理系内でのpHの微少な変化に基づく薗体表面の活性化によるものと推定した.さらに,より実際的な漂白廃液処理プロセスを構築するために,栄養成分要求性が極めて低い高活性廃液分解菌のスクリーニングを試みた.自然界より採集した1212点の腐朽材より,多数のリグニン分解菌を分離し,その中から,何ら栄養成分を添加しなくとも廃液のリグニンを分解する特異なリグニン分解菌であるKS-62株の単離に成功した.さらに,本菌株は漂白廃液の色度,化学的酸素要求量(COD)及び吸着性有機ハロゲン化合物量(AOX)を大幅に減少させうることを明らかにした.このKS-62株の菌体を固定化し,廃液の連続処理を試みたところ,微量のグルコースの存在下,長期間にわたって顕著な脱色とCODの減少が継続されることを認め,リグニン分解菌によるパルプ漂白廃液処理プロセス構築のための基礎的知見を明示した.続きを見る
|目次||1. Introduction 1.1. Chemical components of wood 1.2. General concept of chemical pulping 1.3. Bleaching of kraft pulp 1.4. Composition of bleaching spent liquor 1.5. Treatment of pulp bleaching effluents 1.5.1. Physical and/or chemical treatment 1.5.2. Biological treatment 1.5.3. Treatment with ligninolytic fungi 1.6. Lignin degradation with white-rot fungi 1.7. Lignin biodegradation with white-rot fungus IZU-154 2. Decolorization of Kraft Bleaching Effluents with the Lignin-degrading Fungus IZU-154 2.1. Introduction 2.2. Materials and methods 2.2.1. Microorganisms 2.2.2. Bleaching effluents 2.2.3. Treatment methods of the E_1 effluents 2.2.4. Determination of color units of the E_1 effluents 2.3. Results 2.3.1. Decolorization of the E_1 effluents by the treatment method A 2.3.2. Effects of nutrients on the decolorization of the N-E_1 effluent by the treatment method A 2.3.3. Decolorization of the N-E_1 effluent by the treatment method B 2.4. Discussion 2.5. Summary 3. Detection of Nucleic Acid Constituents in the E_1 Effluent Treated with the Lignin-degrading Fungus IZU-154 3.1. Introduction 3.2. Materials and methods 3.2.1. Microorganisms 3.2.2. Bleaching effluent 3.2.3. Preparation of inoculum 3.2.4. Fungal treatment and analysis of the E_1 effluent 3.3. Results 3.3.1. Analysis of the E_1 effluent treated with IZU-154 3.3.2. Examination of the formations of nucleic acid constituents in the E_1 effluents treated with other lignin-degrading fungi 3.3.3. Effects of preculture conditions of IZU-154 on the formations of nucleic acid constituents and the decolorization of the E_1 effluent 3.3.4. Effects of treatment conditions with IZU-154 on the formations of nucleic acid constituents and decolorization of the E_1 effluent 3.4. Discussion 3.5. Summary 4. An Accelerating Effect of Glucono-$ delta $-lactone on the Decolorization of the E_1 Effluent 4.1. Introduction 4.2. Materials and methods 4.2.1. Microorganisms 4.2.2. Bleaching effluents 4.2.3. Treatment method of the E_1 effluent 4.2.4. Analysis 4.3. Results 4.3.1. Effects of various additives on the decolorization of the E_1 effluent with IZU-154 4.3.2. Effects of glucono-$ delta $-lactone on the decolorization of the El effluent with the lignin-degrading fungi 4.3.3. Consumption and conversion of the additives with C. versicolor 4.3.4. Role of glucono-$ delta $-lactone in the decolorization of the E_1 effluent 4.3.5. Determination of COD in the E_1 effluent during fungal treatment 4.4. Discussion 4.5. Summary 5. Screening of Lignin-degrading Fungi for the Efficient Decolorization and Treatment of the E_1 Effluent without Additional Nutrients with a Newly Found KS-62 5.1. Introduction 5.2. Materials and methods 5.2.1. Isolation of lignin-degrading fungi from decayed wood 5.2.2. Bleaching effluent 5.2.3. Screening of high-decolorization fungi 5.2.4. Physiological characteristics of lignin-degrading fungi 5.2.5. Decolorization of the E_1 effluent with the fungus KS-62 5.2.6. Effect of catalase addition on the decolorization of the E_1 effluent 5.2.7. Analysis 5.3. Results 5.3.1. Screening of fungi having high-decolorlzation activity 5.3.2. Decolorization of the E_1 effluent with lignin-degrading fungi 5.3.3. Physiological characteristics of a lignin-degrading fungus KS-62 5.3.4. Dechlorination and degradation of chlorolignin in the E_1 effluent with lignin-degrading fungi 5.3.5. Extracellular enzymes revealed during the treatment of effluent with KS-62 5.3.6. Effect of catalase addition on the decolorization 5.4. Discussion 5.5. Summary 6. Successive Treatment of the E_1 Effluent with Immobilized Mycelium of the Fungus KS-62 6.1. Intoroduction 6.2 Materials and methods 6.2.1. Microorganisms 6.2.2. Bleaching effluent 6.2.3. Treatment of the E_1 effluent with the immobilized mycelium of white-rot fungi 6.2.4. Analysis 6.3. Results 6.3.1. Treatment of the E_1 effluent with the immobilized mycelium of the white-rot fungi 6.3.2. Effects of glucose concentration on the decolorization with the immobilized mycelium of KS-62 6.4. Discussion 6.5. Summary Acknowledgements References 要約|