Lu Yao, Sun Yaya, Zhang Liang, Zuo Xiaoyu, Li Xiujin, Yuan Hairong
State Key Laboratory of Chemical Resource Engineering, Department of Environmental Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, PR China.
State Key Laboratory of Chemical Resource Engineering, Department of Environmental Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, PR China.
J Environ Manage. 2023 May 1;333:117466. doi: 10.1016/j.jenvman.2023.117466. Epub 2023 Feb 8.
Corn stover (CS) is a promising feedstock for producing biomethane, that can replace diminishing fossil fuels. However, the recalcitrant structure of CS resulted in low degradability in anaerobic digestion (AD). Numerous studies investigated the pretreatment of CS before AD, but the insight mechanism of biomethanation enhancement is not fully revealed. Therefore, this study advanced low-temperature urea-hydrothermal pretreatment of CS, and the biomethane production, substance bioconversion, hydrolase activity, and metagenomic analysis were conducted to unravel the intrinsic mechanisms of pretreatment for the enhanced biomethanation. The results showed that the pretreatment improved 11.5% of the specific surface area of CS, providing 111.5% higher total volatile fatty acids and 19.9% higher reducing sugars than the control, potentially enriching more anaerobic microorganisms. As a result, the pretreated CS achieved 19.1% higher biomethane yield, 9.1% higher volatile solid removal rate, and 3 days shorter digestion time. The mass balance and microbial community succession analysis indicated that the pretreatment reinforced the biomethane conversion from carbohydrate, which was attributed to the rapid enrichment of hydrolytic acidification bacteria (g__unclassified_o__Bacteroidales) (33.2%) and mixotrophic archaea (Methanosarcina) (72.3%). Meanwhile, the activity of cellulase and xylanase was enhanced up to 23.7% and 66.7%. Metagenomic analysis revealed that the combined pretreatment of CS promoted methanogenesis by enhancing various CAZymes secretion (such as oligosaccharide-degrading enzymes), and functional genes expression of hydrolytic, acidification and acetate-methane pathways at days 1-5. The study indicated that the combined pretreatment could influence microbial composition and function by changing the physicochemical properties of the CS, thereby improving methanogenic performance.
玉米秸秆（CS）是一种很有前景的生产生物甲烷的原料，可替代日益减少的化石燃料。然而，CS的顽固结构导致其在厌氧消化（AD）中的降解性较低。众多研究对CS在AD之前的预处理进行了探究，但生物甲烷化增强的内在机制尚未完全揭示。因此，本研究推进了CS的低温尿素 - 水热预处理，并进行了生物甲烷产量、物质生物转化、水解酶活性和宏基因组分析，以阐明预处理促进生物甲烷化增强的内在机制。结果表明，预处理使CS的比表面积提高了11.5%，总挥发性脂肪酸比对照高111.5%，还原糖比对照高19.9%，可能富集了更多厌氧微生物。结果，预处理后的CS生物甲烷产量提高了19.1%，挥发性固体去除率提高了9.1%，消化时间缩短了3天。质量平衡和微生物群落演替分析表明，预处理增强了碳水化合物向生物甲烷的转化，这归因于水解酸化细菌（未分类的g__拟杆菌目_o__）（33.2%）和混合营养古菌（甲烷八叠球菌）（72.3%）的快速富集。同时，纤维素酶和木聚糖酶的活性分别提高了23.7%和66.7%。宏基因组分析表明，CS的联合预处理通过在第1 - 5天增强各种碳水化合物活性酶（如寡糖降解酶）的分泌以及水解、酸化和乙酸 - 甲烷途径的功能基因表达来促进甲烷生成。该研究表明，联合预处理可通过改变CS的物理化学性质来影响微生物组成和功能，从而提高产甲烷性能。
