Preventing Microbial Issues Without SO2

Last Updated: 7/2023

Applies to:Winemakers looking for microbial control in organic, low-input, or canned wines or in situations where SO2 effectiveness is limited like in juice or high pH environments.


Sulfur dioxide (SO2) has been used for millennia to prevent microbial spoilage in food and beverages. However, there are circumstances when SO2 cannot be used or is not effective. For example:

  • Making organic or low-chemical input wines
  • Wine chemistry limits effectiveness of SO2:
    • Pre-fermentation, the antimicrobial action of SO2 is limited because it is bound to sugar and other juice or must components
    • Post-fermentation, the antimicrobial action of SO2 is limited by higher pH, because pH affects how much SO2 is in the antimicrobial (molecular) form
  • Packaging wine in aluminum cans - SO2 must be limited throughout the winemaking process to prevent H2S from developing once canned


Microbial spoilage occurs when unwanted microbial activity results in off-odors, off-flavors, visual flaws, and/or impedes fermentation. Unwanted microbial activity can occur at many stages of winemaking, leading to many different problems. When choosing antimicrobial alternatives to SO2, it is important to understand what type of spoilage can occur at each winemaking stage:



GAIA™ and LEVEL2 INITIA™ are non-Saccharomyces yeasts that are effective pre-fermentation antimicrobial agents. They outcompete indigenous organisms that can produce VA and other off-aromas, initiate alcoholic fermentation, and interfere with inoculated yeast. The antimicrobial activity of GAIA and INITIA are more effective than SO2 pre-fermentation because SO2 can be bound by sugar and other juice or must components.

Both GAIA and INITIA outcompete indigenous microorganisms via a phenomenon known as microbial crowding. Microbial crowding occurs when a microorganism occupies the entire ecological niche through large population numbers. INITIA will also rapidly consume large amounts of oxygen, which further deprives pre-fermentation spoilage organisms of oxygen they require for growth.


DELVOZYME® (LYSOZYME) is an enzyme derived from egg whites that has been used in the food and beverage industry for decades. Lysozyme is compatible with low chemical input and organic winemaking. Its antimicrobial properties come from its ability to cause cell lysis in gram positive bacteria including lactic acid bacteria.

Prior to the introduction of lysozyme to the wine industry, there was no way to target unwanted bacterial populations without affecting the activity of yeast. Lysozyme therefore opened the door to controlling the production of VA during stuck and sluggish fermentations.


Chitosan is an exciting non-allergenic and non-animal-based tool for traditional, vegan, and low chemical input winemaking. NO BRETT INSIDE™ and BACTILESS™ are chitosan-based antimicrobial agents that can be used instead of SO2 to control Brettanomyces spp., lactic acid bacteria and acetic acid bacteria. Both NO BRETT INSIDE and BACTILESS are more effective than SO2 after fermentation, especially in high pH wines.

Chitosan is derived through the deacetylation of chitin which is naturally produced by many living organisms and is the second most abundant polysaccharide on earth after cellulose. Depending on the preparation, chitosan can vary in degree of deacetylation, thus impacting the molecules’ ionic charge, molecular weight, and solubility. By changing one or more of these properties, the functionality of the chitosan molecule changes

The formulations of NO BRETT INSIDE and BACTILESS cause intense electrostatic interactions with negatively charged components on yeast and bacteria cell walls, causing them to attach to the surface of the chitosan and settle out with the product. Additionally, the chitosan can cause cell membrane damage leading to an osmotic and energy imbalance, loss of growth capacity, and eventually cell death.

Note: These products do not completely replace the use of SO2 - BACTILESS, GAIA, Lysozyme, and NO BRETT INSIDE do not offer antioxidant protection, and INITIA only offers antioxidant protection prior to fermentation.

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