生物酶在造纸工业绿色制造中的应用

近年来随着生物技术的发展,生物酶制剂的生产水平不断提高,促进了酶制剂在生物制浆、生物漂白、废纸生物脱墨、酶法纸浆改善性能及树脂生物控制等方面的应用,体现了酶技术在减轻制浆造纸工业环境污染、改善纸浆抄造性能等方面的潜力。文中重点介绍在不同制浆造纸原料及工艺中酶的选用、复配和应用技术及原理,以及酶制剂的应用效率及其对制浆造纸中节能减排和绿色环保的意义。     

生物酶改善溶解浆性能的研究进展

溶解浆由高纯度纤维素组成,用于制造再生纤维素纤维、纤维素酯、纤维素醚等材料。溶解浆性能的好坏对后续产品的生产和加工性能有着很大的影响,其中α-纤维素含量、半纤维素含量、浆粕粘度、灰分、过渡金属离子含量、纤维的物理形态、纤维素分子量分布以及溶解浆的反应性能是其重要的性能指标。生物酶因其绿色、温和、高效的特点,在改善溶解浆性能方面有很好的应用前景,并进行了大量的研究。文中介绍了溶解浆的主要性能指标和改善溶解浆性能的生物酶,重点介绍了纤维素酶和木聚糖酶在改善溶解浆性能方面的应用和研究进展,指出了生物酶改善溶解浆性能目前存在的主要问题,提出了该领域的主要研究方向,并对生物酶处理改善溶解浆性能的技术进行了展望。     

浅析生物工程技术在造纸中的应用

造纸行业要想快速发展,必须改变传统技术,减少环境污染,引用现代生物技术,生物技术在造纸行业的应用,对造纸行业的发展是一个机遇与挑战,本论文从制浆、漂白、改善纤维性能、用生物酶解决树脂障碍、废水处理和酶法脱墨六方面进行阐述生物技术在造纸行业中的应用。     

生物酶和微生物技术改善烟叶香气的研究进展

生物酶和微生物在烟叶醇化发酵过程中发挥着重要作用。目前,利用生物酶和微生物技术提高烟叶品质、改善烟叶香气,已成为烟草行业关注的热点。利用酶制剂处理烟叶可以降解烟叶的蛋白质、果胶、纤维素等生物大分子,以达到提高烟叶品质和改善烟叶香气的作用。利用微生物对烟叶进行发酵可以有效调整和改善烟叶内部化学组分的比例,增加烟叶中的香气物质。综述了生物酶和微生物技术在烟叶产香发酵中的研究进展及其在烟叶发酵机理及增香技术中的应用,重点阐述了微生物和生物酶提高烟叶香气、改善烟叶品质以及降解烟叶中蛋白质、淀粉、果胶、纤维素等大分子物质的研究现状,分析了目前微生物和生物酶在实际应用中存在的问题,以期为今后使用生物酶和微生物技术改善烟叶香气提供理论依据。     

生物酶法制备D-对羟基苯甘氨酸的研究

生物酶法生产D-对羟基苯甘氨酸具有良好的应用前景。通过介绍生物酶法生产D-对羟基苯甘氨酸的研究现状,从酶的分离纯化、酶和细胞的固定化、反应介质研究和反应动力学研究以及基因工程进展几个方面作了总结。     

生物酶法生产生物柴油的研究进展

生物柴油是一种对环境友好的绿色可再生能源,是石油燃料的理想替代品。目前用于制造生物柴油的方法主要有化学法、生物酶法、超临界法。将生物酶法与化学法及超临界法进行了比较,指出了生物酶法具有其他两种方法无法比拟的优势,但酶法也存在着反应效率低、生产成本高的缺点;针对如何提高酶法生产效率及降低生产成本的问题进行了综述,并对生物柴油酶法技术的发展提出了建议。     

意识障碍诊断评估及无创精准治疗

由于意识障碍的病因复杂，个体差异较大，对这类患者的诊断和治疗仍存在较多问题。近年来电生理技术、影像学和精准治疗技术的不断发展使得意识障碍的相关研究取得了诸多实质性进展，包括识别患者残余意识、解释意识恢复的生物学机制以及精准治疗技术对受损神经通路的重建等。本文回顾了意识障碍的诊断评估及无创精准治疗的研究进展，并讨论了新兴技术手段在检测意识水平和预测意识恢复方面的重要作用，提出了该领域目前研究存在的不足之处。期望对相关的研究人员具有一定的指导意义。     

磁性纳米粒子固定化酶技术研究进展

磁性纳米粒子因兼具磁学特性和纳米材料独特性能,被广泛应用于各个领域。就磁性纳米粒子的种类、特性、制备和表面修饰四个方面展开介绍,综述了脂肪酶、漆酶、淀粉酶及其复合酶等生物酶固定化酶技术的最新研究动态,针对磁性纳米粒子在固定化酶技术的研究应用现状进行了总结,以期为磁性纳米粒子固定化酶技术的应用研究提供参考。     

微生物燃料电池生物质能利用现状与展望

作为一种新概念的废物处理与能源化技术,微生物燃料电池研究在过去10年里取得了长足的进步和技术突破。本文在简要介绍微生物燃料电池研究现状基础上,系统综述了该技术及与其他技术耦合在生物质能利用方面的最新研究进展,重点分析了其中存在的问题,并展望了该技术在生物质能转化和利用方面的研究前景。     

VIGS技术在植物基因功能研究中的应用

文章就病毒载体选择、目标基因插入片段设计、病毒嫁接技术、环境条件控制、沉默植株检测等方面对应用病毒诱导的基因沉默(VIGS)技术研究植物基因功能应遵循的基本原则进行介绍,并讨论了其在应用中存在的一些问题。     

The biotechnological control of pitch in paper pulp manufacturing

At present, microbial and enzymatic preparations for the control of triglyceride-containing pitch deposits during the manufacture of mechanical and sulfite paper is commercially available. However, biotechnological products for pitch control in other pulping processes, such as alkaline pulping, are under development. These products include new fungi for the removal of steroids involved in pitch deposit formation in chlorine-free pulps, to be used as a biological pretreatment of wood before pulping. Simultaneously, tailor-made enzymes are being produced using protein-engineering techniques, enabling the specific removal of pitch contaminant compounds from paper pulp.     

Microbial and enzymatic control of pitch in the pulp and paper industry

Pitch control is an important aspect in pulp and paper manufacture, and the first example where microbial biotechnology provided successful solutions in this industrial sector. Triglycerides cause deposits in softwood mechanical pulping, and both microbial and enzymatic products have been commercialized to be applied on wood and pulp, respectively. The former are based on colorless strains of sapstain fungi. The latter are improved lipases, including thermostable variants from directed evolution. These enzymes are among the additives of choice in pulping of high-resin-content softwoods. However, lipases are not useful when pitch originates from other lipids, such as steroids and terpenes, and the sapstain inocula are also only partially effective. In the search for stronger biocatalysts to degrade recalcitrant lipids, the potential of white-rot fungi and their enzymes has been demonstrated. When inocula of these fungi are used, wood treatment must be controlled to avoid cellulose degradation. However, the efficiency and selectivity of the laccase-mediator system permits its integration as an additional bleaching stage. A double benefit can be obtained from these treatments since pitch is controlled at the same time that residual lignin is removed facilitating the implementation of totally chlorine free pulp bleaching.     

Chemical characterization of pitch deposits produced in the manufacturing of high-quality paper pulps from hemp fibers

The composition of pitch deposits occurring in pulp sheets and mill circuits during soda/anthraquinone pulping and elemental chlorine-free pulp bleaching of bast fibers of industrial hemp (Cannabis sativa) was studied. Pitch deposits were extracted with acetone, and the extracts analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). Acetone extracts (15-25% of pitch deposits) were constituted by the defoamers used at the mill and by lipophilic extractives from hemp fibers. Acetone-insoluble residues (75-85% of pitch deposits) were analyzed by pyrolysis-GC/MS in the presence and absence of tetramethylammonium hydroxide. These residues were constituted by salts of fatty acids (arising from hemp fibers) with calcium, magnesium, aluminum and other cations that were identified in the deposits. It was concluded that inappropriate use of defoamer together with the presence of multivalent ions seemed to be among the causes of hemp extractives deposition in the pitch problems reported here.     

The role of microorganisms in the formation of pitch deposits in pulp and paper mills

The cause of pitch deposit formation seems still not fully understood. The work reported here demonstrates that microorganisms effect the agglomeration of emulgated resin droplets and the formation of sticky precipitates.

Pitch deposits from mills consist mainly of ethanol-soluble resins. It is also the ethanol-soluble fraction of wood resins which forms stable emulsions and which is easily agglomerated by microorganisms.

Pitch deposits, collected from various pulp and paper mills, were all found to contain large amounts of microorganisms. Sterile resin emulsions prepared from pitch deposits remained stable over long periods. After inoculation with microorganisms the emulsions were destabilized and the resins completely precipitated as sticky lumps.

Various bacteria and fungi are capable of agglomerating the resins, but species isolated from water, pulp and slime in paper mills were usually most effective. Resins from fresh wood were precipitated at a faster rate than aged resins.

Problems of pitch formation can be considerably reduced when microbial growth is kept under control in the production system. To be effective, the control measures, e.g. slimicides, must be applied at the right place and time, and in the correct concentrations. This presupposes a thorough knowledge of the plant's microbiological condition which can only be obtained by microbiological examination. Practical cases of the appropriate application of biocides in pulp and paper mill systems are discussed.     

Application of enzymes in the pulp and paper industry

The pulp and paper industry processes huge quantities of lignocellulosic biomass every year. The technology for pulp manufacture is highly diverse, and numerous opportunities exist for the application of microbial enzymes. Historically, enzymes have found some uses in the paper industry, but these have been mainly confined to areas such as modifications of raw starch. However, a wide range of applications in the pulp and paper industry have now been identified. The use of enzymes in the pulp and paper industry has grown rapidly since the mid 1980s. While many applications of enzymes in the pulp and paper industry are still in the research and development stage, several applications have found their way into the mills in an unprecedented short period of time. Currently the most important application of enzymes is in the prebleaching of kraft pulp. Xylanase enzymes have been found to be most effective for that purpose. Xylanase prebleaching technology is now in use at several mills worldwide. This technology has been successfully transferred to full industrial scale in just a few years. The enzymatic pitch control method using lipase was put into practice in a large-scale paper-making process as a routine operation in the early 1990s and was the first case in the world in which an enzyme was successfully applied in the actual paper-making process. Improvement of pulp drainage with enzymes is practiced routinely at mill scale. Enzymatic deinking has also been successfully applied during mill trials and can be expected to expand in application as increasing amounts of newsprint must be deinked and recycled. The University of Georgia has recently opened a pilot plant for deinking of recycled paper. Pulp bleaching with a laccase mediator system has reached pilot plant stage and is expected to be commercialized soon. Enzymatic debarking, enzymatic beating, and reduction of vessel picking with enzymes are still in the R&D stage but hold great promise for reducing energy. Other enzymatic applications, i.e., removal of shives and slime, retting of flax fibers, and selective removal of xylan, are also expected to have a profound impact on the future technology of the pulp and paper-making process.     

Main lipophilic extractives in different paper pulp types can be removed using the laccase–mediator system

Lipophilic extractives in wood and other lignocellulosic materials exert a negative impact in pulp and paper manufacturing causing the so-called pitch problems. In this work, the appropriateness of an enzymatic treatment using the laccase–mediator system for pitch biocontrol is evaluated. With this purpose, three pulp types representative for different raw materials and pulping processes—eucalypt kraft pulping, spruce thermomechanical pulping, and flax soda-anthraquinone pulping—were treated with a high-redox-potential laccase from the basidiomycete Pycnoporus cinnabarinus in the presence of 1-hydroxybenzotriazole as a redox mediator. The gas chromatography and gas chromatography/mass spectrometry analyses of the lipophilic extractives from the enzymatically treated pulps revealed that the laccase–mediator treatment completely or greatly removed most of the pitch-causing lipophilic compounds present in the different pulps including: (1) free and conjugated sitosterol in eucalypt paper pulp; (2) resin acids, sterol esters, and triglycerides in spruce pulp; and (3) sterols and fatty alcohols in the flax pulp. Different amounts of free and conjugated 7-oxosterols were found as intermediate products in the oxidation of pulp sterols. Therefore, the laccase–mediator treatment is reported as an efficient method for removing pitch-causing lipophilic compounds from paper pulps obtained from hardwood, softwood, and nonwoody plants.     

Environmental assessment of enzyme assisted processing in pulp and paper industry

Background Aims and Scope  The pulp and paper (P&P) industry is traditionally known to be a large contributor to environmental pollution due its large consumptions of energy and chemicals. Enzymatic processing, however, offers potential opportunities for changing the industry towards more environmentally friendly and efficient operations compared to the conventional methods. The aims of the present study has been to investigate whether the enzyme technology is a more environmentally sound alternative than the conventional ways of producing paper. The study addresses five enzyme applications by quantitative means and discusses the environmental potential of a range of other enzyme applications by qualitative means. Methods  LCA is used as analytical tool and modelling is facilitated in SimaPro software. Foreground LCA data are production/company specific and collected from P&P technology service providers, specific P&P companies and P&P researchers. The background data on energy systems, auxiliary chemicals, etc. are primarily taken from the ecoinvent database. Results  The study shows that fossil energy consumption and potential environmental impacts (global warming, acidification, nutrient enrichment, photochemical smog formation) induced by enzyme production are low compared with the impacts that they save when applied in bleach boosting, refining, pitch control, deinking, and stickies control. Discussion  The general explanation is that small amounts of enzyme provide the same function as large amounts of chemicals and that enzymatic processes generally require less fossil energy inputs than conventional processes. Data quality assessments and sensitivity analyses indicate that this observation is robust for all processes except deinking, although the results are subject to uncertainty and much variation. Conclusions and Recommendations  The environmental improvements that can be achieved by application of enzymatic solutions in the P&P industry are promising. To get a greater penetration of enzymatic solutions in the market and to harvest the environmental advantages of biotechnological inventions, it is recommended that enzymatic solutions should be given more attention in, for instance, ‘Best Available Technology’ notes within the framework of the European Directive on Integrated Pollution Prevention and Control (IPPC). ESS-Submission Editor: Roland Hischier (roland.hischier@empa.ch)     

Microscopy studies reveal delignification and sterol removal from eucalypt kraft pulps by laccase-HBT

Fungal laccases in the presence of mediators are powerful biocatalysts to degrade lignin. Pycnoporus cinnabarinus laccase and 1-hydroxybenzotriazole (HBT) have been successfully used to delignify eucalypt kraft pulp once integrated in a totally chlorine-free bleaching sequence. Real time delignification of kraft pulp by laccase-HBT was verified in situ by monitoring the loss of lignin autofluorescence during the enzymatic treatment using confocal laser scanning microscopy. The highest delignification of pulp fibers occurred over a very short time-span (5 min). Moreover, we demonstrate the removal of sterols, responsible for pitch deposits in hardwood kraft pulps, as an additional effect of laccase-HBT. Spherical structures between pulp fibers localized by low temperature scanning electron microscopy were removed by laccase-HBT. The use of filipin, a specific stain, revealed the sterol nature of many of these structures. At the end of the enzyme-aided bleaching sequence, the fluorescent sterols-filipin signals were almost completely absent.     

Fungal degradation of lipophilic extractives in eucalyptus globulus wood

Solid-state fermentation of eucalypt wood with several fungal strains was investigated as a possible biological pretreatment for decreasing the content of compounds responsible for pitch deposition during Cl2-free manufacture of paper pulp. First, different pitch deposits were characterized by gas chromatography (GC) and GC-mass spectrometry (MS). The chemical species identified arose from lipophilic wood extractives that survived the pulping and bleaching processes. Second, a detailed GC-MS analysis of the lipophilic fraction after fungal treatment of wood was carried out, and different degradation patterns were observed. The results showed that some basidiomycetes that decreased the lipophilic fraction also released significant amounts of polar extractives, which were identified by thermochemolysis as originating from lignin depolymerization. Therefore, the abilities of fungi to control pitch should be evaluated after analysis of compounds involved in deposit formation and not simply by estimating the decrease in the total extractive content. In this way, Phlebia radiata, Funalia trogii, Bjerkandera adusta, and Poria subvermispora strains were identified as the most promising organisms for pitch biocontrol, since they degraded 75 to 100% of both free and esterified sterols, as well as other lipophilic components of the eucalypt wood extractives. Ophiostoma piliferum, a fungus used commercially for pitch control, hydrolyzed the sterol esters and triglycerides, but it did not appear to be suitable for eucalypt wood treatment because it increased the content of free sitosterol, a major compound in pitch deposits.