Li Fan, Foucat Loïc, Bonnin Estelle
INRAE, UR 1268, Biopolymers Interactions Assemblies BIA, F-44316, Nantes, France.
School of Life Sciences, Northeast Normal University, Changchun, 130024, People's Republic of China.
Biotechnol Biofuels. 2021 Apr 28;14(1):107. doi: 10.1186/s13068-021-01957-3.
Pectin plays a role in the recalcitrance of plant biomass by affecting the accessibility of other cell wall components to enzymatic degradation. Elimination of pectin consequently has a positive impact on the saccharification of pectin-rich biomass. This work thus focused on the behaviour of different pectin-degrading enzymes in the presence of low (5%) to high (35%) solid loading of lemon peel.
High solid loading of lemon peel affected pectin solubilisation differently depending on the pectinase used. Pectin lyase was less sensitive to a reduction of water content than was a mixture of endopolygalacturonase and pectin methylesterase, regardless of whether or not the latter's mode of action is processive or not. Marked changes in water mobility were observed along with enzymatic degradation depending on the enzyme used. However, the pectin lyase resulted in less pronounced shifts in water distribution than polygalacturonase-pectin methylesterase mixtures. At similar pectin concentration, pectin solutions hindered the diffusion of hydrolases more than the solid substrate. This can be attributed to the high viscosity of the highly concentrated pectin solutions while the solid substrate may provide continuous diffusion paths through pores.
The increase in solid substrate loading reduced the efficiency of pectin-degrading enzymes catalysing hydrolysis more significantly than those catalysing β-elimination. LF-NMR experiments highlighted the impact of solid loading on water mobility. Compared to other enzymes and whatever the solid loading, pectin lyase led to longer relaxation times linked with the most destructuration of the solid substrate. This new information could benefit the biorefinery processing of pectin-rich plant material when enzymes are used in the treatment.
果胶通过影响其他细胞壁成分对酶解的可及性，在植物生物质的顽固性中发挥作用。因此，去除果胶对富含果胶的生物质糖化有积极影响。这项工作因此聚焦于不同果胶降解酶在低（5%）至高（35%）固含量柠檬皮存在时的行为。
柠檬皮的高固含量对果胶溶解的影响因所用果胶酶而异。果胶裂解酶对水分含量降低的敏感性低于内切多聚半乳糖醛酸酶和果胶甲酯酶的混合物，无论后者的作用模式是否具有连续性。随着酶解反应的进行，根据所用酶的不同，观察到水流动性有明显变化。然而，果胶裂解酶导致的水分布变化比聚半乳糖醛酸酶 - 果胶甲酯酶混合物引起的变化不那么明显。在相似的果胶浓度下，果胶溶液比固体底物更能阻碍水解酶的扩散。这可归因于高浓度果胶溶液的高粘度，而固体底物可能通过孔隙提供连续的扩散路径。
固体底物负载量的增加对催化水解的果胶降解酶效率的降低比对催化β - 消除反应的酶更显著。低频核磁共振实验突出了固体负载量对水流动性的影响。与其他酶相比，无论固体负载量如何，果胶裂解酶导致的弛豫时间更长，这与固体底物的最大破坏有关。当在处理中使用酶时，这一新信息可能有利于富含果胶的植物材料的生物炼制加工。
