Du Zhumei, Yamasaki Seishi, Oya Tetsuji, Cai Yimin
College of Animal Science and Technology, Yangzhou University, Yangzhou, 225009, People's Republic of China.
Japan International Research Center for Agricultural Sciences (JIRCAS), Tsukuba, Ibaraki, 305-8686, Japan.
Biotechnol Biofuels Bioprod. 2023 Aug 4;16(1):125. doi: 10.1186/s13068-023-02368-2.
Feed shortage is an important factor limiting livestock production in the world. To effectively utilize natural woody plant resources, we used wilting and microbial additives to prepare an anaerobic fermentation feed of mulberry, and used PacBio single-molecule real-time (SMRT) sequencing technology to analyse the "enzyme-bacteria synergy" and fermentation mechanism.
The fresh branches and leaves of mulberry have high levels of moisture and nutrients, and also contain a diverse range of epiphytic microorganisms. After ensiling, the microbial diversity decreased markedly, and the dominant bacteria rapidly shifted from Gram-negative Proteobacteria to Gram-positive Firmicutes. Lactic acid bacteria (LAB) emerged as the dominant microbial population, resulting in increased in the proportion of the carbohydrate metabolism and decreased in the proportion of the amino acid and "global and overview map" (GOM) metabolism categories. The combination of cellulase and LAB exhibited a synergistic effect, through which cellulases such as glycanase, pectinase, and carboxymethyl cellulase decomposed cellulose and hemicellulose into sugars. LAB converted these sugars into lactic acid through the glycolytic pathway, thereby improving the microbial community structure, metabolism and fermentation quality of mulberry silage. The GOM, carbohydrate metabolism, and amino acid metabolism were the main microbial metabolic categories during ensiling. The presence of LAB had an important effect on the microbial community and metabolic pathways during silage fermentation. A "co-occurrence microbial network" formed with LAB, effectively inhibiting the growth of harmful microorganisms, and dominating the anaerobic fermentation process.
In summary, PacBio SMRT was used to accurately analyse the microbial network information and regulatory mechanism of anaerobic fermentation, which provided a scientific basis for the study of woody silage fermentation theory. This study reveals for the first time the main principle of the enzyme-bacteria synergy in a woody silage fermentation system, which provides technical support for the development and utilization of woody feed resources, and achieves sustainable livestock production.
饲料短缺是限制全球畜牧业生产的一个重要因素。为有效利用天然木本植物资源，我们采用萎蔫和微生物添加剂制备了桑椹厌氧发酵饲料，并利用PacBio单分子实时（SMRT）测序技术分析了“酶 - 菌协同作用”及发酵机制。
桑椹鲜枝叶含水量和营养成分含量高，还含有多种附生微生物。青贮后，微生物多样性显著降低，优势菌迅速从革兰氏阴性变形菌门转变为革兰氏阳性厚壁菌门。乳酸菌成为优势微生物种群，导致碳水化合物代谢比例增加，氨基酸和“全局及概述图”（GOM）代谢类别比例降低。纤维素酶和乳酸菌的组合表现出协同效应，通过这种效应，聚糖酶、果胶酶和羧甲基纤维素酶等纤维素酶将纤维素和半纤维素分解为糖。乳酸菌通过糖酵解途径将这些糖转化为乳酸，从而改善了桑椹青贮饲料的微生物群落结构、代谢和发酵品质。GOM、碳水化合物代谢和氨基酸代谢是青贮过程中的主要微生物代谢类别。乳酸菌的存在对青贮发酵过程中的微生物群落和代谢途径有重要影响。与乳酸菌形成了一个“共现微生物网络”，有效抑制了有害微生物的生长，并主导了厌氧发酵过程。
综上所述，利用PacBio SMRT准确分析了厌氧发酵的微生物网络信息和调控机制，为木本青贮发酵理论研究提供了科学依据。本研究首次揭示了木本青贮发酵系统中酶 - 菌协同作用的主要原理，为木本饲料资源的开发利用提供了技术支持，实现了畜牧业的可持续生产。
