The Technical Department of Inter Rhone is leading a research project in conjunction with the University Institute of Vine and Wine in Dijon. The object of the research is to better understand the biofilm lifestyle of Brettanomyces and its link with resistance to cleaning agents.
Brett yeasts are the most damaging microorganisms found in wine and can contaminate wine during fermentation and/or during breeding. Their ability to survive under stressful conditions, particularly by forming a biofilm, makes it more difficult to eliminate them.
The research compared two methods for cleaning winery equipment, testing each method on a variety of Brett strains. The first method, called the “reference” method, uses a solution of foaming caustic soda with 5% peroxide. The biofilms were treated with this solution for 15 minutes.
The second method was a more ecological approach to cleaning. The biofilms were treated with a 5% lactic acid solution for 15 minutes. In both cases, five strains of Brettanomyces from differing origins were used.
The results showed a significant reduction of cultivable cells in 4 out of 5 Brett strains treated with lactic acid; however, the treatment did not completely eliminate cells. One strain proved more tolerant of the lactic acid solution.
The strains treated with the chemical solution showed two strains were more tolerant of the chemical method. Flow cytometry showed these two strains contained viable remaining cells with entry into a viable but non cultivable state (VBNC). The VBNC state is a stress response strategy in which cells retain metabolic activity but cannot grow as long as the stress continues. The VBNC state is extremely risky for the quality of the wine. With the disappearance of the stress, these cells can resume their growth and possibly engender an alteration.
The lactic acid solution, under the conditions tested, is not sufficient for the eradication of Brett, but it represents a promising and ecologically sustainable approach. Further testing with longer contact and higher concentrations will be needed in order to ultimately reduce the use of chemicals in the production of wine.
Source: Inter Rhône
For more information, we recommend reading a recent article published in the journal IVES on the ability to form biofilms by Brettanomyces yeasts:
Brettanomyces bruxellensis biofilms: a lifestyle to withstand environmental stresses?