Cao Xiaohui, Cai Rui, Zuo Sasa, Niu Dongze, Yang Fuyu, Xu Chuncheng
College of Engineering, China Agricultural University, (East Campus), 17 Qing-Hua-Dong-Lu, Haidian District, Beijing, 100083, People's Republic of China.
School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Hubei Province, China.
Bioresour Bioprocess. 2024 Jan 22;11(1):14. doi: 10.1186/s40643-024-00730-2.
Traditional autoclaving, slow degradation rate and preservation of biomass treated by fungi are the main factors restricting biological treatment. In our previous studies, strains with high efficiency and selective lignin degradation ability were obtained. To further solve the limiting factors of biological treatment, this paper proposed a composite treatment technology, which could replace autoclaves for fungal treatment and improve the preservation and utilization of fungal-pretreated straw. The autoclaved and expanded buckwheat straw were, respectively, degraded by Irpex lacteus for 14 days (CIL, EIL), followed by ensiling of raw materials (CK) and biodegraded straw of CIL and EIL samples with Lactobacillus plantarum for different days, respectively (CP, CIP, EIP). An expansion led to lactic acid bacteria, mold, and yeast of the samples below the detection line, and aerobic bacteria was significantly reduced, indicating a positive sterilization effect. Expansion before I. lacteus significantly enhanced lignin selective degradation by about 6%, and the absolute content of natural detergent solute was about 5% higher than that of the CIL. Moreover, EIL decreased pH by producing higher organic acids. The combination treatment created favorable conditions for ensiling. During ensiling, EIP silage produced high lactic acid about 26.83 g/kg DM and the highest acetic acid about 22.35 g/kg DM, and the pH value could be stable at 4.50. Expansion before I. lacteus optimized the microbial community for ensiling, resulting in EIP silage co-dominated by Lactobacillus, Pediococcus and Weissella, whereas only Lactobacillus was always dominant in CP and CIP silage. Clavispora gradually replaced Irpex in EIP silage, which potentially promoted lactic acid bacteria growth and acetic acid production. In vitro gas production (IVGP) in EIL was increased by 30% relative to CK and was higher than 24% in CIL. The role of expansion was more significant after ensiling, the IVGP in EIP was increased by 22% relative to CP, while that in CIP silage was only increased by 9%. Silage of fungal-treated samples reduced methane emissions by 28% to 31%. The study demonstrated that expansion provides advantages for fungal colonization and delignification, and further improves the microbial community and fermentation quality for silage, enhancing the nutrition and utilization value. This has practical application value for scaling up biological treatment and preserving the fungal-treated lignocellulose.
传统高压灭菌、真菌处理生物质的降解速率缓慢以及生物质保存是限制生物处理的主要因素。在我们之前的研究中，获得了具有高效和选择性木质素降解能力的菌株。为了进一步解决生物处理的限制因素，本文提出了一种复合处理技术，该技术可以替代高压灭菌器进行真菌处理，并提高真菌预处理秸秆的保存和利用率。将经高压灭菌和膨化的荞麦秸秆分别用乳白耙齿菌降解14天（CIL、EIL），然后分别将原料（CK）以及CIL和EIL样品的生物降解秸秆与植物乳杆菌进行不同天数的青贮（CP、CIP、EIP）。膨化使样品中的乳酸菌、霉菌和酵母菌低于检测线，需氧菌显著减少，表明具有积极的杀菌效果。在乳白耙齿菌处理前进行膨化显著提高了木质素选择性降解约6%，天然洗涤剂溶质的绝对含量比CIL高约5%。此外，EIL通过产生更高含量的有机酸降低了pH值。联合处理为青贮创造了有利条件。在青贮过程中，EIP青贮产生的乳酸含量高，约为26.83 g/kg DM，乙酸含量最高，约为22.35 g/kg DM，pH值可稳定在4.50。乳白耙齿菌处理前的膨化优化了青贮的微生物群落，导致EIP青贮以乳杆菌属、片球菌属和魏斯氏菌属共同主导，而在CP和CIP青贮中只有乳杆菌属始终占主导地位。在EIP青贮中，克鲁维酵母逐渐取代了乳白耙齿菌，这可能促进了乳酸菌的生长和乙酸的产生。EIL的体外产气（IVGP）相对于CK增加了30%，高于CIL中的24%。膨化在青贮后的作用更为显著，EIP的IVGP相对于CP增加了22%，而CIP青贮中的IVGP仅增加了9%。真菌处理样品的青贮使甲烷排放量减少了28%至31%。该研究表明，膨化有利于真菌定殖和脱木质素，并进一步改善青贮的微生物群落和发酵质量，提高营养和利用价值。这对于扩大生物处理规模和保存真菌处理的木质纤维素具有实际应用价值。
