Neysens Patricia, Messens Winy, Gevers Dirk, Swings Jean, De Vuyst Luc
Research Group of Industrial Microbiology, Fermentation Technology and Downstream Processing (IMDO), Department of Applied Biological Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
Laboratory Microbiology Gent Culture Collection, Ghent University, B-9000 Gent, Belgium.
Microbiology (Reading). 2003 Apr;149(Pt 4):1073-1082. doi: 10.1099/mic.0.25880-0.
Micro-organisms used during the production of fermented foods are subjected to several abiotic stresses. Microbial survival during these processes strongly depends on the ability of the cells to adapt and become more tolerant to the environmental conditions. Cultivation of Lactobacillus amylovorus DCE 471, a potential strain for use during type II sourdough fermentations, at low temperatures, unfavourable pH and high salt concentrations resulted in biphasic growth patterns. In addition, two separate bacteriocin peaks, as well as a dramatic change in cellular morphology, were observed. In general, an increase of the specific bacteriocin production occurred during the second growth phase. Finally, the observed sugar consumption profiles were affected by the applied fermentation temperature. Moreover, the highest bacteriocin activity occurred during maltose consumption at a low constant temperature of 28 degrees C and a constant pH of 5.4. Plate counts from both growth phases revealed the existence of two colony types. Irregular colonies were found to outnumber smoother colonies during the first growth phase, while the second growth phase was characterized by a greater number of smooth colonies. Electron microscopy was used to investigate the observed morphological switch at the single-cell level. Single, rod-shaped cells changed into elongated cells that grew in chains. Colony and cell morphology changes coincided with the biphasic growth pattern.
发酵食品生产过程中使用的微生物会受到多种非生物胁迫。这些过程中微生物的存活很大程度上取决于细胞适应并变得更耐受环境条件的能力。在低温、不利pH值和高盐浓度下培养II型酸面团发酵中潜在使用的菌株解淀粉乳杆菌DCE 471，导致了双相生长模式。此外，还观察到两个单独的细菌素峰以及细胞形态的显著变化。一般来说，在第二个生长阶段，细菌素的特定产量增加。最后，观察到的糖消耗曲线受所应用的发酵温度影响。此外，在28摄氏度的低温和5.4的恒定pH值下消耗麦芽糖期间，细菌素活性最高。两个生长阶段的平板计数显示存在两种菌落类型。在第一个生长阶段，发现不规则菌落的数量超过较光滑菌落，而第二个生长阶段的特征是较光滑菌落数量更多。电子显微镜用于在单细胞水平研究观察到的形态转变。单个杆状细胞变成了成链生长的细长细胞。菌落和细胞形态的变化与双相生长模式一致。
