Glucose metabolism in Lactococcus lactis MG1363 under different aeration conditions: requirement of acetate to sustain growth under microaerobic conditions.
Lactococcus lactis subsp. lactis MG1363 was grown in batch cultures on a defined medium with glucose as the energy source under different aeration conditions, namely, anaerobic conditions, aerobic conditions, and microaerobic conditions with a dissolved oxygen tension of 5% (when saturation with air was used as the reference). The maximum specific growth rate was high (0.78 to 0.91 h(-1)) under all aeration conditions but decreased with increasing aeration, and more than 90% of the glucose was converted to lactate. However, a shift in by-product formation was observed. Increasing aeration resulted in acetate, CO(2), and acetoin replacing formate and ethanol as end products. Under microaerobic conditions, growth came to a gradual halt, although more than 60% of the glucose was still left. A decline in growth was not observed during microaerobic cultivation when acetate was added to the medium. We hypothesize that the decline in growth was due to a lack of acetyl coenzyme A (acetyl-CoA) needed for fatty acid synthesis since acetyl-CoA can be synthesized from acetate by means of acetate kinase and phosphotransacetylase activities.
Nordkvist
Mikkel
M
Center for Process Biotechnology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Jensen
Niels Bang Siemsen
NB
Villadsen
John
J
D000085:Acetates / Q000378:metabolism; D000332:Aerobiosis; D000693:Anaerobiosis; D018533:Biomass; D003470:Culture Media; D005947:Glucose / Q000378:metabolism*; D013294:Lactococcus lactis / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism
D000085:Acetates; D003470:Culture Media; D005947:Glucose