Background As a renewable carbon source, biomass energy not only helps in resolving the management problems of lignocellulosic wastes, but also helps to alleviate the global climate change by controlling environmental pollution raised by their generation on a large scale. However, the bottleneck problem of extensive production of biofuels lies in the filamentous crystal structure of cellulose and the embedded connection with lignin in biomass that leads to poor accessibility, weak degradation and digestion by microorganisms. Some pretreatment methods have shown significant improvement of methane yield and production rate, but the promotion mechanism has not been thoroughly studied. Revealing the temporal and spatial effects of pretreatment on lignocellulose will greatly help deepen our understanding of the optimization mechanism of pretreatment, and promote efficient utilization of lignocellulosic biomass. Here, we propose an approach for qualitative, quantitative, and location analysis of subcellular lignocellulosic changes induced by alkali treatment based on label-free Raman microspectroscopy combined with chemometrics. Results Firstly, the variations of rice straw induced by alkali treatment were characterized by the Raman spectra, and the Raman fingerprint characteristics for classification of rice straw were captured. Then, a label-free Raman chemical imaging strategy was executed to obtain subcellular distribution of the lignocellulose, in the strategy a serious interference of plant tissues' fluorescence background was effectively removed. Finally, the effects of alkali pretreatment on the subcellular spatial distribution of lignocellulose in different types of cells were discovered. Conclusions The results demonstrated the mechanism of alkali treatment that promotes methane production in rice straw through anaerobic digestion by means of a systemic study of the evidence from the macroscopic measurement and Raman microscopic quantitative and localization two-angle views. Raman chemical imaging combined with chemometrics could nondestructively realize qualitative, quantitative, and location analysis of the lignocellulose of rice straw at a subcellular level in a label-free way, which was beneficial to optimize pretreatment for the improvement of biomass conversion efficiency and promote extensive utilization of biofuel.

中文翻译：

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亚细胞木质纤维素的定量可视化揭示碱预处理促进稻草产甲烷的机制。

背景作为一种可再生碳源，生物质能不仅有助于解决木质纤维素废物的管理问题，还有助于通过大规模控制其产生的环境污染来缓解全球气候变化。然而，大规模生产生物燃料的瓶颈问题在于纤维素的丝状晶体结构以及与生物质中木质素的嵌入连接，导致可及性差，微生物降解和消化能力差。一些预处理方法已显示出甲烷产率和产率的显着提高，但促进机制尚未深入研究。揭示预处理对木质纤维素的时空效应将大大有助于加深我们对预处理优化机制的理解，促进木质纤维素生物质的有效利用。在这里，我们提出了一种基于无标记拉曼显微光谱结合化学计量学的碱处理引起的亚细胞木质纤维素变化的定性、定量和定位分析方法。结果首先利用拉曼光谱表征碱处理稻草的变化规律，获取稻草分类的拉曼指纹特征。然后，采用无标记拉曼化学成像策略获得木质纤维素的亚细胞分布，该策略有效去除了植物组织荧光背景的严重干扰。最后，发现了碱预处理对不同类型细胞中木质纤维素亚细胞空间分布的影响。结论 通过对宏观测量和拉曼微观定量和定位两个角度的证据的系统研究，结果表明碱处理通过厌氧消化促进稻草产生甲烷的机理。拉曼化学成像结合化学计量学可以在亚细胞水平上无损实现稻草木质纤维素的无标记定性、定量和定位分析，有利于优化预处理，提高生物质转化效率，促进广泛利用的生物燃料。结论 通过对宏观测量和拉曼微观定量和定位两个角度的证据的系统研究，结果表明碱处理通过厌氧消化促进稻草产生甲烷的机理。拉曼化学成像结合化学计量学可以在亚细胞水平上无损实现稻草木质纤维素的无标记定性、定量和定位分析，有利于优化预处理，提高生物质转化效率，促进广泛利用的生物燃料。结论 通过对宏观测量和拉曼微观定量和定位两个角度的证据的系统研究，结果表明碱处理通过厌氧消化促进稻草产生甲烷的机理。拉曼化学成像结合化学计量学可以在亚细胞水平上无损实现稻草木质纤维素的无标记定性、定量和定位分析，有利于优化预处理，提高生物质转化效率，促进广泛利用的生物燃料。