Metabolically engineered lactic acid bacteria and their use
AssigneeChr. Hansen A/S
InventorDan Nilsson
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Abstract
Mutants of lactic acid bacteria including Lactococcus lactis which are defective in pyruvate formate-lyase production and/or in their lactate dehydrogenase (Ldh) production and methods of isolating such mutants or variants are provided. The mutants are useful in the production of food products or in the manufacturing of compounds such as diacetyl, acetoin and acetaldehyde and as components of food starter cultures. In particular, Lactococcus lactis DN223 deposited under the accession No. DSM 11036.
Claims21
A method of isolating a pyruvate formate-lyase (Pfl) and lactate dehydrogenase (Ldh) defective Lactococcus lactis lactic acid bacterium which is not capable of growth under anaerobic conditions in the presence of acetate, said method comprising
- (i) selecting a Pfl defective Lactococcus lactis lactic acid bacterium, and
- (ii) selecting from said Pfl defective lactic acid bacterium a strain which is incapable of growing under anaerobic conditions in an acetate-containing medium, wherein the strain of Lactococcus lactis selected in (ii) is the Pfl and Ldh defective strain of
- wherein at least 15% of pyruvate being catabolized by the Pfl and Ldh defective strain of Lactococcus lactis lactic acid bacterium selected in step (ii) is converted to acetoin.
A biologically pure culture of a non-recombinant Pfl and Ldh defective mutant Lactococcus lactis lactic acid bacterium which is non-naturally occuring and which is not capable of growing under anaerobic conditions in the presence of acetate.
Dependencies are inferred from the claim text.