Three Phases of Malolactic Fermentation Bacteria

2017 was the first year that we had any reasonable amount of Chardonnay grapes for fermentation. The Chardonnay came in with approximately 10 g/L titratable acids so we wanted to convert some of the malic acid to lactic acid.
Oenococcus oeni is the lactic acid bacteria commonly used in malolactic fermentation (MLF). When grape sugars are available, O. oeni will ferment these sugars as their primary source of carbon for growth.
MLF is a survival mechanism that supplies energy to the bacteria when other nutrients become scarce. MLF converts naturally occurring malic acid to lactic acid, through the decarboxylation of L-malate to L-lactate.
Malolactic bacteria are present in low concentrations on grapes, approximately 100 cells/g, but then they increase to 10⁴ cells/mL after crush and 10⁷ cells/mL by the end of alcoholic fermentation when malolactic fermentation typically occurs. The metabolism of sugars and organic acids during malolactic fermentation can be divided into three phases:

• During the growth phase (Phase I), sugar catabolism occurs with little production of acetic and lactic acid; minimal citric and malic acid are metabolised in this phase
• As the bacterial cell numbers increase above 5 × 10⁶ cfu/mL during Phase II, the catabolism of sugar ceases and malic acid metabolism proceeds accompanied by production of lactic acid; citric acid remains untouched at this stage, and there is no acetic acid produced during malic acid degradation.
• Phase III is characterized by the metabolism of citric acid accompanied by an increase in acetic acid. The increase of lactic acid content in the wine results in a softer mouth-feel and the acetic acid contributes to the volatile acidity of the wine

When my husband added our packaged MBR31 for the MLF we expected some visible (by paper chromatography) results in two weeks. Given all that these bacterial helpers need to do for growth, maybe we need to be a little more patient.
References:
1. Scott Laboratories Malolactic Bacteria.
2. Swiegers, Jan, Bartowsky, Eveline, Henschke, P.A. & Pretorius, I.S., Microbial modulation of wine aroma and flavour, Australian Journal of Grape and Wine Research, 2005, 11. 139 - 173. 10.1111/j.1755-0238.2005.tb00285.x.
3. Whitney Lysbeth Beaman, Effect of Cell Density and Growth Phase on Malolactic Fermentation by Oenococcus oeni, May, 2011.
3. The Australian Wine Research Institute, Achieving Successful Malolactic Fermentation
Other related blogs:
Malolactic Fermentation
Diacetyl Formation