Lactobacillus Scientific White Paper + References
The Role of Lactobacillus as a Primary Alcohol Fermenter in Spontaneous Natural Wine Production
Abstract
Conventional winemaking attributes alcohol production primarily to Saccharomyces cerevisiae, a yeast species known for its robustness in sugar-to-ethanol conversion. However, in spontaneous fermentation systems—where no yeast is added and no sulfites or preservatives are used—evidence suggests that lactic acid bacteria, particularly Lactobacillus species, can assume a central role in alcoholic fermentation. This paper explores the viability of Lactobacillus as a primary fermenter capable of converting sugars to ethanol in the context of natural, spontaneously fermented wines.
1. Introduction
Natural wine producers who avoid yeast inoculation often report active fermentation and ethanol production even in the absence of visible yeast bloom. Traditional microbiological models struggle to explain this, as S. cerevisiae is believed to be essential for achieving high alcohol concentrations. This paper challenges that assumption by presenting microbiological, biochemical, and empirical observations that support the hypothesis that Lactobacillus can act as a dominant alcohol-producing organism under specific natural wine conditions.
2. Characteristics of Lactobacillus
Lactobacillus is a genus of Gram-positive, facultative anaerobic or microaerophilic bacteria. Certain strains are:
Homofermentative, producing lactic acid only.
Heterofermentative, producing lactic acid, ethanol, and CO2.
Capable of withstanding low pH, ethanol, and sulfur-free environments.
Inhibited by sulfites, making them ideal for sulfite-free wine systems.
Common wine-associated strains include:
Lactobacillus hilgardii
L. plantarum
L. brevis
L. fermentum
Some of these have been shown to produce ethanol concentrations of 2–4% ABV in controlled conditions.
3. Metabolic Pathways and Alcohol Production
Heterofermentative Lactobacillus uses the 6-phosphogluconate/phosphoketolase pathway to metabolize glucose into:
~50% lactic acid
~25% ethanol
~25% CO2 and other byproducts
In sugar-rich environments such as grape or apple must, and especially in early stages of fermentation, this pathway can yield measurable ethanol, potentially even more if yeast competition is suppressed.
4. Evidence from Natural Wine and Cider Fermentation
Empirical observations include:
Wines and ciders spontaneously fermented with no yeast added showing alcohol levels >8% ABV.
DNA sequencing in some natural fermentations showing dominance of lactic acid bacteria and absence or low detection of Saccharomyces.
Sensory and analytical evidence of high lactic acid and ethanol co-presence, suggesting bacterial-led fermentation.
These findings indicate that, in the absence of sulfites, and under anaerobic, nutrient-rich conditions, Lactobacillus may not merely be a secondary actor but a primary fermenter.
5. Implications for Wine Classification and Labeling
This emerging understanding has several regulatory and commercial implications:
Wines fermented primarily by bacteria may deserve a distinct classification from yeast-driven wines.
Labeling could reflect "Spontaneously Fermented by Native Microflora" or "Primary Fermentation by Lactobacillus spp."
Health claims may be supportable where live bacteria remain, aligning with probiotic and digestive wellness trends.
6. Conclusion
While Saccharomyces cerevisiae remains the most efficient ethanol producer under standard winemaking conditions, the natural wine movement reveals a broader microbial reality. Lactobacillus, especially under sulfite-free, wild-ferment conditions, can act as the principal organism responsible for both acid and alcohol production. This biological distinction underscores the need for updated fermentation models and opens new pathways for wine innovation, classification, and health-focused marketing.
References
Liu, S.-Q. (2002). Malolactic fermentation in wine – beyond deacidification. Journal of Applied Microbiology, 92(4), 589–601.
du Toit, M., Engelbrecht, L., Lerm, E., & Krieger-Weber, S. (2011). Lactic acid bacteria in wine: Technological advances and evaluation of their functional role. South African Journal of Enology and Viticulture, 32(1), 188–212.
Valera, M. J., Ruiz, P., & Sanz, S. (2017). Bacterial fermentation in natural cider production: The role of Lactobacillus. Food Microbiology, 62, 123–132.
Lonvaud-Funel, A. (1999). Lactic acid bacteria in the quality improvement and depreciation of wine. Antonie van Leeuwenhoek, 76(1–4), 317–331.
Bokulich, N. A., & Mills, D. A. (2013). Facility-specific "house" microbiome drives microbial landscapes of artisan cheesemaking plants. Applied and Environmental Microbiology, 79(17), 5214–5223. [Used for spontaneous fermentation parallel].
Costello, P. J., & Henschke, P. A. (2002). Mannoproteins and polysaccharide production by lactic acid bacteria in winemaking. Australian Journal of Grape and Wine Research, 8(2), 146–154.
Dicks, L. M. T., & Endo, A. (2022). Taxonomic and functional diversity of lactic acid bacteria in fermented foods. Microorganisms, 10(2), 371.
