Xu Zhenshang, He Huiying, Zhang Susu, Guo Tingting, Kong Jian
State Key Laboratory of Microbial Technology, Shandong UniversityJinan, China.
Front Microbiol. 2017 Jun 2;8:941. doi: 10.3389/fmicb.2017.00941. eCollection 2017.
Lactic acid bacteria (LAB) play important roles in silage fermentation, which depends on the production of sufficient organic acids to inhibit the growth of undesirable microorganisms. However, LAB are not able to degrade cellulose and hemicellulose. Bacteria and fibrolytic enzymes are usually used as inoculants to improve the silage quality and digestibility. In the present study, we isolated four strains ( CGMCC 11056, CCTCC AB2010208, CCTCC AB2016237 and CCTCC AB2010204) with feruloyl esterase (FAE) activities from ensiled corn stover (CS) by a plate screening assay. The genes encoding FAEs were cloned and hetero-expressed in . The optimal temperature and pH of these purified enzymes ranged from 45 to 50°C and from 7.0 to 8.0, respectively. They could hydrolyze hydroxycinnamoyl esters in a substrate-specific manner when methyl ferulate, methyl caffeate, methyl ρ-coumarate and methyl sinapinate were used as substrates. Moreover, these four FAEs were able to hydrolyze CS to release hydroxycinnamic acids. Furthermore, these strains could degrade hydroxycinnamic esters, and CGMCC 11056 was the most efficient strain among these four isolates. These results provided a new target for the development of inoculants to improve silage quality and digestibility.
乳酸菌（LAB）在青贮饲料发酵中发挥着重要作用，青贮饲料发酵依赖于产生足够的有机酸来抑制有害微生物的生长。然而，乳酸菌无法降解纤维素和半纤维素。细菌和纤维分解酶通常用作接种剂以提高青贮饲料的质量和消化率。在本研究中，我们通过平板筛选试验从青贮玉米秸秆（CS）中分离出四株具有阿魏酸酯酶（FAE）活性的菌株（CGMCC 11056、CCTCC AB2010208、CCTCC AB2016237和CCTCC AB2010204）。对编码FAEs的基因进行了克隆并在[此处原文缺失具体宿主信息]中进行异源表达。这些纯化酶的最适温度和pH分别为45至50°C和7.0至8.0。当以阿魏酸甲酯、咖啡酸甲酯、对香豆酸甲酯和芥子酸甲酯作为底物时，它们能够以底物特异性方式水解羟基肉桂酸酯。此外，这四种FAEs能够水解玉米秸秆以释放羟基肉桂酸。此外，这些菌株能够降解羟基肉桂酸酯，并且CGMCC 11056是这四株分离物中最有效的菌株。这些结果为开发提高青贮饲料质量和消化率的接种剂提供了新的靶点。
