Metabolically engineered lactic acid bacteria and their use
OwnerDan Nilssoninventor
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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 manufacturing of compounds such as diacetyl, acetoin and acetaldehyde and as components of food starter cultures.
Claims30
An Ldh defective lactic acid bacterium of the genus Lactococcus, said bacterium having Pfl activity, which bacterium is capable of growing anaerobically.
A method of isolating a pyruvate formate-lyase (Pfl) defective lactic acid bacterium, the method comprising the steps of
- (i) providing a wild-type lactic acid bacterial strain which under aerobic conditions is not capable of growth in the absence of acetate in a medium not containing lipoic acid, but which is capable of growth is such medium under anaerobic conditions, and
- (ii) selecting from said wild-type strain a mutant which under said conditions essentially does not grow in the absence of acetate.
A Pfl and Ldh defective mutant lactic acid bacterium which is not capable of growing under anaerobic conditions in the presence of acetate, and having, relative to a wild-type lactic acid bacterium or a Pfl defective mutant strain, at least one of the following characteristics:
- (i) essentially the same growth yield when cultivated under aerobic conditions in M17 medium,
- (ii) a reduced capability of converting lactose to lactate,
- (iii) an increased production of α-acetolactate, and/or
- (iv) an increased production of an α-acetolactate derived metabolite
- said bacterium being of the genus Lactoccus.
Dependencies are inferred from the claim text.