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林业科学 ›› 2020, Vol. 56 ›› Issue (3): 127-143.doi: 10.11707/j.1001-7488.20200314

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假木质素沉积及对纤维素酶解的影响研究进展

沙如意1,2,3,4,张沙沙1,余瞻1,赵福权1,蔡成岗1,3,4,肖竹钱1,3,4,毛建卫1,3,4,*   

  1. 1. 浙江科技学院生物与化学工程学院 杭州 310023
    2. 浙江省废弃生物质循环利用与生态处理技术重点实验室 杭州 310023
    3. 浙江省农产品化学与生物加工技术重点实验室 杭州 310023
    4. 浙江省农业生物资源生化制造协同创新中心 杭州 310023
  • 收稿日期:2017-11-30 出版日期:2020-03-01 发布日期:2020-04-21
  • 通讯作者: 毛建卫
  • 基金资助:
    浙江省重点研发计划项目(2015C02031);国家级星火计划项目(2015GA700079);浙江科技学院浙江省废弃生物质循环利用与生态处理技术重点实验室开放基金项目(2016REWB32);河南省工业微生物资源与发酵技术重点实验室开放基金项目(IMRFT20180206);省属高校基本科研业务费专项资金项目(2019JL10)

Advances in Pseudo-Lignin Deposition and Its Effects on Enzymatic Hydrolysis of Cellulose

Ruyi Sha1,2,3,4,Shasha Zhang1,Zhan Yu1,Fuquan Zhao1,Chenggang Cai1,3,4,Zhuqian Xiao1,3,4,Jianwei Mao1,3,4,*   

  1. 1. School of Biological and Chemical Engineering, Zhejiang University of Science and Technology Hangzhou 310023
    2. Key Laboratory of Recycling and Eco-Treatment of Waste Biomass of Zhejiang Province Hangzhou 310023
    3. Zhejiang Provincial Key Laboratory for Chemical and Biological Processing Technology of Farm Products Hangzhou 310023
    4. Zhejiang Provincial Collaborative Innovation Center of Agricultural Biological Resources Biochemical Manufacturing Hangzhou 310023
  • Received:2017-11-30 Online:2020-03-01 Published:2020-04-21
  • Contact: Jianwei Mao

摘要:

木质纤维素类生物质是地球上最丰富的可再生资源。为提高木质纤维素类生物质的转化率,提升纤维素酶的水解效率和可发酵性糖产量,降低纤维素酶的使用量和生物质转化成本,对木质纤维素类生物质进行预处理十分必要;然而,木质素、纤维素和半纤维素之间的天然屏障限制了纤维素酶对纤维素组分的酶解。木质纤维素类生物质预处理主要有物理法、化学法、物理化学法和生物法,目前更多采用质量分数小于4%的稀酸法(如盐酸、硫酸和硝酸等,120~210 ℃)、高温热水法、蒸汽爆破法和液相水热法等,不同预处理方法对木质素或大部分半纤维素的溶解和去除有利于提高纤维素酶的可及性。木质素对纤维素酶解具有明显抑制作用,通过预处理降低木质素含量有利于提高纤维素酶解效率。木质纤维经稀酸或高温热水等预处理后,Klason木质素相对含量反而会增加。在木质纤维素类生物质预处理过程中,木质素液滴可能以假木质素形式沉积于纤维素表面,使其比天然木质素更加抑制纤维素酶解。本研究首先概述生物质预处理过程中木质素液滴和假木质素的形成过程,提出假木质素产生的可能机制,并对其组成和性质进行综述;然后阐述木质素液滴和假木质素对木质纤维酶解的影响;最后总结假木质素形成的调控策略。假木质素的形成过程属于非均相反应过程,受传质扩散(分子水平)和流动(宏观统计水平)的影响,可从介尺度行为研究假木质素的形成机制,同时建立相关模型和理论实现其科学的定量描述和定向调控,这不仅有利于木质纤维素类生物质炼制工艺的发展,也有利于促进跨学科科学规模的形成。

关键词: 木质纤维, 假木质素, 纤维素酶, 生物质

Abstract:

Lignocellulosic biomass is one of the most abundant renewable resources on earth. In order to improve the conversion rate of lignocellulosic biomass, increase the enzymatic hydrolysis efficiency of cellulose and the yield of fermentable sugars and to reduce the usage of cellulase and the conversion cost of biomass, it is essential to obtain the pretreated lignocellulosic biomass. However, the natural barrier between lignin, cellulose and hemicellulose limits the availability of cellulase to the cellulose components encapsulated inside. The main pretreatment methods of lignocellulose covered physical method, chemical method, physical chemical method and biological method. At present, the more adopted pretreatment methods include the dilute acid(hydrochloric acid, sulfuric acid, nitric acid, etc.)with the mass fraction less than 4% at the temperature of 120-210℃, high temperature hot water method, steam explosion method and liquid hydrothermal method. The dissolution and removal of lignin or most of the hemicellulose by various pretreatment methods is beneficial to improve cellulase accessibility. At present, a large number of studies have shown that lignin can significantly inhibit the enzymatic hydrolysis of cellulose, pretreatment can reduce lignin content and improve the efficiency of cellulose hydrolysis. In recent years, studies have shown that the relative content of Klason lignin would increase after the pretreatment of lignocellulose under severe conditions by using dilute acid and high temperature water. During the pretreatment processes of lignocellulosic biomass, lignin droplets may be deposited on the surface of the cellulose in the form of pseudo-lignin, so that it can inhibit cellulase hydrolysis more than natural lignin. However, no relevant review paper was found in the published articles. In this paper, the formation processes of lignin droplets and pseudo-lignin during the pretreatment of biomass were described. The possible mechanisms of pseudo-lignin production were put forward, and its composition and properties were reviewed. On this basis, the effects of lignin droplets and pseudo-lignin on the enzymatic hydrolysis of lignocellulose were summarized. Finally, the effects of lignin droplet and pseudo-lignin on the enzymatic hydrolysis of cellulose were discussed, and then the regulation strategy of pseudo-lignin formation was summarized. The authors believe that it is of great significance to study the mechanisms, structure characteristics, regulation mechanisms of the production of pseudo-lignin in the process of biorefinery. The formation of pseudo-lignin is a heterogeneous reaction process. At the same time, the formation mechanisms of pseudo-lignin can be studied from the mesoscale behavior due to the influence of mass transfer(molecular level)and the flow(macroscopic statistical level), and at the same time, the related models and theories should be established to realize their scientific quantitative descriptions and regulation. Moreover, it is beneficial to the development of lignocellulosic biomass refining processes and also it is conducive to promote the formation and development of an interdisciplinary scale of science.

Key words: lignocellulose, pseudo-lignin, cellulase, biomass

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