Biphasic kinetics of growth and bacteriocin production with Lactobacillus amylovorus DCE 471 occur under stress conditions.
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.
Neysens
Patricia
P
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.
Messens
Winy
W
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.
Gevers
Dirk
D
Laboratory Microbiology Gent Culture Collection, Ghent University, B-9000 Gent, Belgium.
Swings
Jean
J
Laboratory Microbiology Gent Culture Collection, Ghent University, B-9000 Gent, Belgium.
De Vuyst
Luc
L
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.
D015373:Bacterial Typing Techniques; D001430:Bacteriocins / Q000096:biosynthesis*; D018533:Biomass; D001939:Bread / Q000382:microbiology; D003470:Culture Media; D004269:DNA, Bacterial / Q000032:analysis; D005285:Fermentation; D005632:Fructose / Q000378:metabolism; D018869:Heat-Shock Response; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019344:Lactic Acid / Q000378:metabolism; D007779:Lactobacillus acidophilus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000648:ultrastructure; D008320:Maltose / Q000378:metabolism; D008954:Models, Biological; D016133:Polymerase Chain Reaction / Q000379:methods
D001430:Bacteriocins; D003470:Culture Media; D004269:DNA, Bacterial; D005632:Fructose; D019344:Lactic Acid; D008320:Maltose