Method of improving biomass yield of lactic acid bacterial cultures

Abstract

A method of enhancing biomass yield of a lactic acid bacterial species cell culture, comprising cultivating the cells in a process comprising the steps of providing conditions that results in a reduced glycolytic flux and providing conditions that enable the cells to have, under aerobic conditions, a respiratory metabolism. The increased yield of biomass may be the result of an increased yield of ATP which can be obtained by activating the native ATP synthase activity of the H + -ATPase complex by lowering the ATP/ADP ratio, e.g. by carbon source limitation, and/or by increasing the proton gradient (membrane potential) of the cells, e.g. by enhancing or establishing an electron transport chain which can be achieved by enhancing expression of dehydrogenases or electron transport chain components, by adding to the medium a quinone or porphyrin compound or by enhancing the expression of the H + -ATPase activity.

1 - 28 . (canceled)  
     
     
         29 . A method of reducing the content of by-products in a production of biomss of lactic acid bacterial cells said method comprising of a step on increasing the yield of biomass by (I) providing in the cell conditions that results in a reduced glycolytic flux and (ii) providing conditions that enables the cell under aerobic conditions to have a respiratory metabolism.  
     
     
         30 . A lactic acid bacterial cell obtainable by an increased yield of biomass of a lactic acid bacterial cell culture, the yield exceeding that which can be obtained at maximum from substrate level phosphorylation, the method of comprising the steps of 
 (i) providing in the cells of the culture conditions that result in a reduced glycolytic flux, and    (ii) providing conditions that enable the cells under aerobic conditions to have a respiratory metabolism.    
     
     
         31 . A lactic acid bacterial cell produced by culturing the cell under conditions that results in a reduced glycolytic flux, and under conditions that enable the cells to have, under aerobic conditions, a respiratory metabolism, said cell having, relative to a lactic acid bacterial cell produced in the presence of a readily metabolised carbon source in excess, an increased activity of the enzymes involved in the uptake and/or degradation of a that carbon source in which the bacterial cell has been propagated, and containing a detectable amount of a porphyrin compound and/or a cytochrome.  
     
     
         32 . A lactic acid bacterial cell according to  claim 31  which constitutively expresses the lac operon and/or gal operon.  
     
     
         33 . A lactic acid bacterial cell according to  claim 32  wherein constitutive expression is provided by a mutation in the gene coding for the lac repressor and/or lac operon.  
     
     
         34 . A lactic acid bacterial cell according to  claim 31  that contains at least 0.1 ppm on a dry matter basis of a porphyrin compound.  
     
     
         35 . A lactic acid bacterial cell according to  claim 31  that contains at least 0.1 ppm on a dry matter basis of cytochrome.  
     
     
         36 . A lactic acid bacterial cell according to  claim 31  which is a cell of a lactic acid bacterial species selected from the group consisting of a  Lactococcus  species, a  Streptococcus  species, a  Leuconostoc  species, a  Lactobacillus  species and an  Oenococcus  species.  
     
     
         37 . A starter culture comprising the lactic acid bacterial culture or a lactic acid bacterial cell according to  claim 30 .  
     
     
         38 . A composition according to  claim 37  where the composition is in the form of frozen, liquid or freeze-dried composition.  
     
     
         39 . A composition according to  claim 37  containing an amount of viable culturally modified lactic acid bacterial cells which is in the range of 10 4  and 10 12  CFU per g.  
     
     
         40 . A composition according to  claim 37  that comprises cells of two or more different lactic acid bacterial strains.  
     
     
         41 . A composition according to  claim 37  which further comprises at least one component enhancing the viability of the bacterial cell during storage, including a bacterial nutrient and/or a cryoprotectant.