制浆造纸生物技术研究进展

制浆造纸工业是国民经济的主要支柱之一,但也是资源消耗和环境污染的大户。近年来,国外用于制浆造纸工业的生物技术研究异常活跃,除废水生物处理外,木聚糖酶助漂、脂肪酶控制树脂、木片真菌预处理和酶法废纸脱墨等工艺已经在生产中得到实际应用,生物制浆、漆酶漂白工艺也已进入中试阶段。结合以草浆为主的特点,我国的制浆造纸生物技术研究也已日趋活跃起来。     

Effect of surfactant and particle size reduction on hydrolysis of deinking sludge and nonrecyclable newsprint

Disposal of sludge from deinking mills represents a significant proportion of operating costs. Bioconversion of the cellulosic fraction of deinking sludge (DIS) to ethanol greatly reduces disposal costs while producing an environmentally friendly fuel. In this study, the cellulosic fraction of newsprint and deinking sludge was hydrolysed to produce fermentable sugars. For newsprint, a particle size of 1 to 1.5 mm provided optimal reaction rates in batch reactors over practical hydrolysis times, and reducing sugar concentrations as high as 35 g/L could be achieved using a fed-batch reactor configuration. For both newsprint and DIS, the hydrolysis rate increased nonlinearly with enzyme loading. Tween-80 only marginally improved sugar production but was able to release sugars from cellulosic substrates in the absence of lytic enzymes, in an amount proportional to the surfactant concentration and the substrate particle size. DIS was relatively recalcitrant to enzymatic hydrolysis, possibly due in part to inhibition by hydrophobic constituents. (c) 1995 John Wiley & Sons, Inc.     

Characterisation and application of glycanases secreted by Aspergillus terreus CCMI 498 and Trichoderma viride CCMI 84 for enzymatic deinking of mixed office wastepaper

Two enzymatic extracts obtained from xylan-grown Aspergillus terreus CCMI 498 and cellulose-grown Trichoderma viride CCMI 84 were characterised for different glycanase activities. Both strains produce extracellular endoxylanase and endoglucanase enzymes. The enzymes optimal activity was found in the temperature range of 45–60 °C. Endoglucanase systems show identical activity profiles towards temperature, regardless of the strain and inducing substrate. Conversely, the endoxylanases produced by both strains showed maximal activity at different pH values (from 4.5 to 5.5), being the more acidic xylanase produced by T. viride grown on cellulose. The endoglucanase activities have an optimum pH at 4.5–5.0. The endoxylanase and endoglucanase activities exhibited high stability at 50 °C and pH 5.0. Mannanase, β-xylosidase, and amylase activities were also found, being the first two activities only present for T. viride extract. These two enzymatic extracts were used for mixed office wastepaper (MOW) deinking. When the enzymatic extract from T. viride was used, a further increase of 24% in ink removal was obtained by comparison with the control. Both enzymes contributed to the improvement of the paper strength properties and the obtained results clearly indicate that the effective use of enzymes for deinking can also contribute to the pulp and paper properties improvement.     

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)     

Role of various enzymes for deinking paper: a review

Paper manufacturing industries depend mainly on forests for wood, which is the basic raw material. Forest plays an important role in balancing the ecosystem to protect forest deinking and bleaching (recycling) of waste paper had gained a lot of importance. Conventional chemical deinking processes require large amount of chemicals which are toxic and hazardous to the environment, hence other effective deinking methods are needed. Enzymatic deinking (cellulolytic, hemicellulolytic and ligninolytic) has attracted enormous attention because of high efficacy and minimum environmental impact. For bleaching, enzymatic action (individual as well as in combination), along with physical treatment, makes the pulp more accessible to the chemicals and also to the amount of chemicals required to obtain similar levels of brightness. Strength properties and brightness of the pulp are improved by these treatment methods. With minimum impact on the environment, this review gives comprehensive information about the various methods used for the recycling of waste paper.