State Key Laboratory of Agrobiotechnology, MOA Key Laboratory of Soil Microbiology and National Energy R & D Center for Non-food Biomass, College of Biological Sciences, China Agricultural University, Beijing, 100193 China.
Biotechnol Biofuels. 2014 Sep 10;7(1):130. doi: 10.1186/s13068-014-0130-x. eCollection 2014.
The efficiency and cost of current lignocellulosic enzymes still limit the large-scale production of cellulosic ethanol in industry. Residual lignin after pretreatment severely depresses the activity of polysaccharide hydrolases and the h ydrolysis of holocellulose. If we include in hydrolase mixture construction the ligninase involved in lignin degradation, which mainly includes laccase, manganese peroxidases (MnP) and lignin peroxidase (LiP), it is feasible that this could greatly improve the fermentable sugars yield.
The psychrophilic lignocellulosic enzymes system of Cladosporium cladosporioides Ch2-2 including ligninase and polysaccharide hydrolases was suitable for selective delignification and efficient saccharification of biomass with wide thermal adaptability. The purified laccase was optimally active at 15°C and pH 3.5, exhibiting high thermostability over a broad range of temperatures (between 4 and 40°C). In addition, manganese-independent peroxidase (MIP), a special type of ligninase with the capacity to oxidize dimethyl phthalate (DMP) in the absence of H2O2 and Mn(2+), was optimally active at 20°C and pH 2.5, exhibiting high thermostability over a broad range of temperatures (4 and 28°C), while depressed completely by Fe(2+) and essentially unaffected by EDTA. Synergy between Ch2-2 crude enzymes and commercial xylanase obviously enhanced biomass hydrolysis, which could take the place of expensive commercial cellulase mixture. The maximum value of synergistic degree reached 4.7 at 28°C, resulting in 10.1 mg/mL reducing sugars.
The psychrophilic enzymes system of C. cladosporioides Ch2-2 with a different synergistic mechanism has huge potential for the enhancement of biomass hydrolysis at mesophilic and low temperatures. The application scope of the lignocellulosic enzyme cocktail could be greatly enlarged by optimizing the operation conditions specific to the characteristics of ligninase.
目前木质纤维素酶的效率和成本仍然限制了纤维素乙醇在工业上的大规模生产。预处理后的残余木质素严重抑制了多糖水解酶和全纤维素的水解。如果在水解酶混合物的构建中加入参与木质素降解的木质素酶，主要包括漆酶、锰过氧化物酶（MnP）和木质素过氧化物酶（LiP），那么这将极大地提高可发酵糖的产量。
深冷木纤维素酶系统包括木质素酶和多糖水解酶，适用于生物质的选择性脱木质素和高效糖化，具有广泛的热适应性。纯化的漆酶在 15°C 和 pH3.5 时活性最佳，在 4 至 40°C 的较宽温度范围内具有较高的热稳定性。此外，锰非依赖性过氧化物酶（MIP）是一种特殊类型的木质素酶，能够在没有 H2O2 和 Mn(2+)的情况下氧化邻苯二甲酸二甲酯（DMP），最适活性在 20°C 和 pH2.5，在较宽的温度范围内（4 和 28°C）具有较高的热稳定性，而完全被 Fe(2+)抑制，基本不受 EDTA 影响。Ch2-2 粗酶与商业木聚糖酶的协同作用明显增强了生物质水解，可替代昂贵的商业纤维素酶混合物。在 28°C 时协同度的最大值达到 4.7，产生 10.1mg/mL 的还原糖。
C. cladosporioides Ch2-2 的低温酶系统具有不同的协同作用机制，在中温和低温下增强生物质水解具有巨大的潜力。通过优化特定于木质素酶特性的操作条件，可以大大扩大木质纤维素酶鸡尾酒的应用范围。
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