MLF biochemistry

What are the advantages to wine of MLF?

• reduction in acidity

• microbial stability

• flavour modification

• decarboxylation of L-malic acid by the malolactic enzyme = 0.2 unit increase pH, TA decreases

• bacteria is mediated

What do the more variable genes in O.oeni than sacc equal?

enormous diversity

o.oeni is best adapated species of LAB for wine

What are there pH factors that influence the growth of LAB?

• minimum pH = 2.9

• greater % of o.oeni strains can metabolise sugars at pH 3.5 than at 3.1

• importance of bacterial membrane function in maintaining intracellular pH above extracellular pH - membrane improved bacteria

• more ATP produced at lower pH

What wine factors impact LAB?

• pH

• SO2

• EtOH

• temp

• interaction with yeast

• malic acid concentration

• lactic acid concentration

• nutrients

• fungicide residues

• inhibitors that will influence growth

What are the characteristics of an inhibitory interaction between wine yeast and MLF bacteria?

• production of bioactive yeast metabolites

• competition for nutrients

• production of ethanol

  • varying sensitivity

• production of SO2

• medium chain FA

• antibacterial yeast metabolites - protein

What are the characteristics of an stimulatory interaction between wine yeast and MLF bacteria?

• yeast autolysis

  • nitrogenous components - AA, peptides, proteins

  • release of vitamins, nucleotides and lipids

• glucans

• mannoproteins

  • can absorb medium chained FA