Fraunhofer Marion E, Jakob Frank, Vogel Rudi F
Lehrstuhl für Technische Mikrobiologie, Technische Universität München, Gregor-Mendel-Straße 4, 85354, Freising, Germany.
Curr Microbiol. 2018 Jul;75(7):794-802. doi: 10.1007/s00284-018-1450-z. Epub 2018 Feb 13.
We wanted to identify key factors influencing the extent of β-glucan production by Lactobacillus brevis TMW 1.2112, which has been isolated from viscous, spoiled beer and which could contribute to viscosity increases of spoiled beverages via exopolysaccharide (EPS) production. In this way, we analyzed the influence of different initial pH values and carbohydrate sources on growth of and slime/β-glucan formation by this strain. In a screening of 48 carbohydrates, 14 fermentable sugars which enabled growth were identified. These sugars were further investigated regarding their EPS formation-promoting properties. The hexose-based mono- and di-saccharides enabled slime formation, while all pentoses failed to cause any thickening effect. The strongest slime formation was observed upon growth on D-maltose, the weakest on D-fructose. A lower initial pH (4.3) caused significant higher viscosities than an initially higher one (pH 6.2). This effect was independent from the carbohydrate supplied. Although the thickening of nutrient media by L. brevis TMW 1.2112 strongly depended on the initial pH and the available carbon source, all isolated polysaccharides were exclusively composed of glucose moieties and exhibited highly similar elution profiles after separation via asymmetric flow field-flow fractionation independently of the provided carbon source. Our results suggest that the extent of β-glucan/slime formation by special L. brevis strains isolated from the brewery environment is strongly influenced by the initial pH and the availability of certain EPS formation-promoting sugars with maltose being the most favored carbohydrate for the regulated and directive biosynthesis of capsular β-glucan.
我们想要确定影响短乳杆菌TMW 1.2112产生β-葡聚糖程度的关键因素，该菌株是从变黏、变质的啤酒中分离出来的，它可能通过产生胞外多糖（EPS）导致变质饮料的粘度增加。通过这种方式，我们分析了不同初始pH值和碳水化合物来源对该菌株生长以及黏液/β-葡聚糖形成的影响。在对48种碳水化合物的筛选中，确定了14种能够支持生长的可发酵糖。进一步研究了这些糖促进EPS形成的特性。基于己糖的单糖和二糖能够形成黏液，而所有戊糖都未能产生任何增稠效果。在以D-麦芽糖为生长底物时观察到最强的黏液形成，以D-果糖为底物时最弱。较低的初始pH值（4.3）比较高的初始pH值（6.2）导致的粘度显著更高。这种影响与所提供的碳水化合物无关。尽管短乳杆菌TMW 1.2112对营养培养基的增稠强烈依赖于初始pH值和可用碳源，但所有分离出的多糖均仅由葡萄糖部分组成，并且在通过非对称流场-流分级分离后，无论提供何种碳源，都呈现出高度相似的洗脱曲线。我们的结果表明，从啤酒厂环境中分离出的特殊短乳杆菌菌株形成β-葡聚糖/黏液的程度受到初始pH值和某些促进EPS形成的糖的可用性的强烈影响，其中麦芽糖是用于荚膜β-葡聚糖的调控和定向生物合成的最有利碳水化合物。
