Fermenting Beer with Lallemand Sourvisiae Yeast

Published: November 19, 2025 at 12:34:28 AM UTC

Lallemand Sourvisiae Yeast is a bioengineered sour yeast, developed by Mascoma and marketed by Lallemand under LalBrew/Sourvisiae. This strain of Saccharomyces cerevisiae produces lactic acid during primary fermentation. This allows for one-step souring and alcoholic fermentation in a single vessel.

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Key Takeaways

Lallemand Sourvisiae Yeast performs one-step souring and fermentation by producing lactic acid during primary fermentation.
The strain is a bioengineered Saccharomyces cerevisiae developed by Mascoma and sold under LalBrew/Sourvisiae.
This Sourvisiae review focuses on metrics brewers need: acid production, attenuation, and temperature range.
Available through Lallemand distributors and referenced in White Labs partnership listings for U.S. breweries.
The following sections cover handling, fermentation dynamics, repitching, and regulatory notes relevant to commercial use.

What is Sourvisiae and how it was engineered

Sourvisiae is a bioengineered Saccharomyces cerevisiae strain, engineered to produce lactic acid during primary fermentation. The company behind it employed targeted modification, avoiding random changes. This method ensures a consistent and predictable fermentation process for brewers.

The key alteration involves the insertion of a lactate dehydrogenase gene from Rhizopus oryzae, a food microorganism. Mascoma engineering used a codon-optimized version of this gene, controlled by the strong ADH1 promoter. The PDC1 terminator was used to drive expression during fermentations. The construct was integrated into the yeast genome by recombination, ensuring no extrachromosomal elements remain.

By introducing an efficient LDH enzyme, the modified yeast redirects pyruvate away from ethanol production and towards lactic acid. Most eukaryotes can produce lactic acid, but brewer’s yeast typically favors alcohol. The single, well-placed change shifts this balance while preserving core fermentation traits.

The product is a GMO sour yeast, submitted for regulatory review. Lallemand and Mascoma provided safety and performance data during approvals. Regulators examined strain-specific information as part of their evaluation. Brewers should treat the strain as a genetically modified organism and follow local labeling or reporting rules.

Genetic change: single integrated lactate dehydrogenase gene.
Expression system: ADH1 promoter and PDC1 terminator for fermentation-phase activity.
Stability: genome integration by recombination for long-term stability.
Regulatory context: product-specific documentation provided by Mascoma engineering and Lallemand.

The manufacturer has not publicly named the exact parental strain. Independent observers note performance similarities with common ale strains such as US-05, suggesting a Chico-like background. However, this remains unconfirmed. The focus for brewers is predictable lactic acid production from a single, well-characterized modification, rather than wholesale changes to fermentation character.

Why brewers choose Lallemand Sourvisiae Yeast

Many breweries opt for Lallemand Sourvisiae due to its clear advantages. It offers a quick, dependable souring solution. This yeast enables one-step souring by producing lactic acid during primary fermentation. This process streamlines brewing, reducing kettle work and shortening the overall schedule.

The benefits extend beyond efficiency. Sourvisiae is a clean sour yeast, designed to avoid the funky esters and complex metabolites associated with Brettanomyces or mixed bacteria. It delivers a tart, focused profile with fewer off-flavors, ensuring consistent results from batch to batch.

Commercial brewers are increasingly drawn to its operational advantages. One-step souring reduces the time needed for sour ales and minimizes cross-contamination risks. For those focused on brewery efficiency, the labor and tank occupancy savings are substantial.

Predictability is key for maintaining quality control. Data from the manufacturer and independent tests show consistent pH values and lactic acid levels. Many brewers achieve consistent terminal pH by day 5 under standard conditions. This makes planning packaging and sales timelines more straightforward.

Styles like Berliner Weisse, kettle sours, and other light, tart ales benefit from this approach. Brewers seeking the advantages of Sourvisiae often highlight its repeatable acidity, simpler cellar workflows, and faster release cadence as compelling reasons to adopt it.

Typical brewing properties and performance metrics

Lallemand Sourvisiae exhibits medium-to-high attenuation, as documented. White Labs indicates typical Sourvisiae attenuation at 76–82%. Brewers might observe lower apparent attenuation due to lactic acid production, which alters density without increasing residual sugar.

Standard worts at 20°C typically reach a final pH of 3.0 to 3.2. Independent bench trials achieved a terminal final pH of 3.1–3.2 by day five in small-volume tests.

Lactic acid concentration ranges from about 8 to 15 g/L under typical conditions. This concentration is crucial for perceived sourness and can influence mouthfeel and stability.

Fermentations with Sourvisiae are vigorous and complete quickly. Lallemand reports primary activity in 4–7 days at 20°C (68°F). Bench fermentations in 50 mL vessels reached target attenuation and pH by day five.

Flocculation is reported as high, aiding rapid clearing once fermentation slows.
Alcohol tolerance in product specifications is approximately 10–15% ABV, suitable for many beer styles.

Product microbiological specs support reliable use at scale. Dry yeast solids are typically 93–97%. Viability is specified at ≥5 x 10^9 CFU per gram, with wild yeast and bacteria counts usually below 1 per 10^6 cells. Lallemand notes absence of diastaticus in the datasheet.

When planning with Sourvisiae, balance target gravity, expected Sourvisiae attenuation, and desired lactic acid concentration to reach the final pH you want. Monitor gravity and pH during the first week to confirm fermentation speed and to anticipate flocculation and alcohol tolerance limits for the recipe.

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Optimal fermentation conditions and temperature range

Lallemand suggests an ideal temperature range of 15–22°C (59–72°F) for Sourvisiae to achieve clean acidification in traditional sour beers. The broader fermentation range spans 10–22°C (50–72°F), offering brewers flexibility in aligning yeast activity with style objectives.

Standard test metrics are reported from wort at 20°C (68°F). Under these conditions, typical outputs include a pH near 3.0–3.2 and lactic acid levels in the 8–15 g/L range. This baseline facilitates comparison of attenuation and acid curves across batches.

Expect vigorous fermentation and acidification to conclude in about 4–7 days under recommended fermentation conditions. Independent trials indicate many batches reach terminal gravity and target pH by day five, provided pitch rate, nutrition, and temperature remain consistent.

It's crucial to monitor lag phase and attenuation sensitivity. Pitch rate, yeast handling, oxygen levels, and wort nutrition significantly influence performance. Avoid temperature shock during rehydration and transfer steps to minimize stress and the risk of petite mutants, which can harm viability.

Use consistent temperature control to keep Sourvisiae fermentation temperature within the optimal temperature range.
Monitor pH and gravity daily in early stages to confirm acidification and sugar uptake are on track.
Store unopened dry yeast vacuum-sealed below 4°C (39°F); follow shelf guidance for opened packs.

Good wort oxygenation before pitching and stable fermentation conditions after pitching lead to a faster start and cleaner flavors. Small adjustments within the recommended range allow for tuning acidity while preserving yeast health.

Pitching, rehydration, and handling best practices

To achieve reliable fermentations with Lallemand Sourvisiae, adhere to specific pitching guidelines. Aim for a Sourvisiae pitching rate of 50–100 g/hL, which equates to 2.5–5 million viable cells per mL. This range aligns with both manufacturer advice and White Labs' recommendations for consistent souring performance.

Rehydration of Sourvisiae enhances cell viability, especially in challenging ferments. Begin by sprinkling dry yeast onto water at 30–35°C (86–95°F) in a clean container, using about ten times the yeast weight. Allow it to sit for 15 minutes, then stir and rest for five minutes before gradually acclimating it to the wort temperature.

For acclimation, add small amounts of wort in five-minute intervals until the temperatures match. Then, inoculate the cooled wort without delay to minimize stress. This method reduces contamination risk and supports a strong lag phase.

In high-gravity or stressful conditions, consider using a rehydration nutrient like Go-Ferm Protect Evolution. Go-Ferm aids in restoring membrane integrity and boosts early fermentation vigor. It's a wise choice when following pitching guidelines for demanding beers.

Dry-pitching directly into wort is suitable for many ales and lower-stress batches. However, opt for rehydration for high-gravity, high-hopping, or when yeast age and storage conditions might compromise viability. Select the method based on the beer style and your risk tolerance.

Proper storage and handling are crucial for maintaining cell health. Store vacuum-sealed packs below 4°C and verify vacuum integrity before use. Avoid using 500 g packs that have lost vacuum. Once opened, reseal under vacuum if possible and use the remainder promptly, as air exposure significantly reduces activity.

Effective handling minimizes downtime and preserves cell health. Prepare sanitation, temperature control, and any Go-Ferm solution in advance. Follow the recommended Sourvisiae pitching rate and rehydration steps to ensure each batch has the best start.

Fermentation dynamics and monitoring with Sourvisiae

Sourvisiae fermentation dynamics exhibit consistent acidification during the active phase. Bench tests indicate pH and attenuation nearing terminal values by day 5 at 20°C. It's crucial for brewers to understand that lactic acid formation consumes fermentable sugar. This process does not proportionally decrease density, making apparent attenuation misleading.

For accurate results, monitoring pH and gravity together is essential. A clear fermentation timeline helps distinguish between sugar metabolism and acid production. Expect vigorous activity between days 4 and 7 at standard pitch and temperature.

Pitch-rate effects on terminal acidity are modest with Sourvisiae. Typical recommended pitch rates yield consistent final pH across a broad range of starting gravities. Only severe under-pitching materially reduces acidification, unlike some Lachancea strains used in souring.

Gravity effects are muted when the culture is pitched correctly. Sourvisiae tends to reach similar terminal pH values from low to moderate original gravities. Track specific gravity as a fermentation control, but interpret apparent attenuation cautiously because lactic acid lowers sweetness without always changing density proportionally.

Practical monitoring steps:

Record gravity and pH daily during the first week to establish the fermentation timeline.
Use calibrated pH meters and hydrometers or refractometers corrected for alcohol.
Check cell viability before re-pitching or blending to confirm active acid producers.

Routine lab checks reduce surprises when scaling recipes. Combining gravity trends with monitoring pH gives a more complete picture of fermentation progress and acid development than relying on one metric alone.

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Repitching and yeast stability considerations

Lallemand advises brewers to steer clear of repitching Sourvisiae. The product literature warns that low pH and acidic conditions can severely impact cell viability and fermentation performance. Many breweries opt for a single-brew strategy to mitigate risks and ensure consistent production.

Genetic studies from Mascoma and Lallemand reveal the LDH modification exhibits remarkable GMO gene stability across numerous generations. This suggests the inserted trait remains stable under laboratory conditions. Independent bench repitch tests have confirmed steady terminal pH levels over several cycles, with viable cell counts reaching around 2.5 million per milliliter per cycle.

In commercial environments, practical limitations come into play. Sourvisiae exhibits a slower generation time, approximately 4.6 hours, compared to common ale strains at around 3.3 hours. This slower growth rate makes it vulnerable to being outcompeted by other yeasts or bacteria in mixed cultures or contaminated environments. Such dynamics limit the reliable longevity of repitching in production settings.

For those considering repitching Sourvisiae, it's crucial to monitor acid production and the population's composition closely. Regularly track pH and viable cell counts during each cycle. Additionally, perform periodic plating or qPCR to detect contamination and shifts in strain composition.

Many breweries view Sourvisiae as a single-use or short-run material. Fresh yeast is generally considered safer for maintaining predictable souring. When consistency is paramount, it's advisable to avoid repitching and use new inoculum to preserve yeast stability and control over the process.

Competition, mixed cultures, and contamination risks

Sourvisiae grows slower than typical ale strains. Its generation time is around 4.62 hours, based on independent hourly growth curves. In contrast, US-05, Nottingham, and W34-70 have generation times ranging from 3.27 to 3.63 hours. This disparity in growth rates means faster strains can outcompete Sourvisiae in mixed environments.

Working with mixed cultures can lead to a rapid shift in population dynamics. A small initial presence of a fast-growing strain can quickly dominate. Modeling and plating trials indicate that a single contamination event, at about one cell per million, can become detectable within eight to twelve generations. At this stage, the souring yeast can be diluted, and the beer's intended acidity is lost.

Practical detection methods include simple agar techniques. Chalk-wort plates with 0.1% chalk reveal acid producers by clear halos. Experiments have shown US-05 can outcompete mixed populations by generation twelve in a 1:1,000,000 starting mix. This highlights the need for routine monitoring when Sourvisiae and higher-growth strains share equipment or repitching lines.

The risk of Sourvisiae contamination increases with serial repitches and shared handling. Its slower growth means sour character can be overwhelmed by even modest contamination. This risk is further heightened when co-pitching with vigorous ale strains or when cleaning protocols are lax.

Keep single-strain fermentations when possible to protect souring performance.
Avoid co-pitching with high-growth strains like US-05 unless monitoring is in place.
Use strict separation, cleaning, and dedicated transfer lines to reduce cross-contamination.
Plate samples periodically to check population balance during repitch cycles.

Implementing these measures can help mitigate Sourvisiae contamination risk and preserve the intended flavor. Regular checks and conservative repitching strategies are essential to counteract the competitive growth rates of common brewing yeasts.

Flavor profile and sensory expectations

The Sourvisiae flavor profile is marked by a tangy, sharply acidic taste. Lallemand notes that the yeast imparts a bright, slightly fruity aroma with distinct lactic notes. Brewers should anticipate a focused lactic sour character, without the complexity of barnyard or Brett-like tones.

Acidity in Sourvisiae is notably high. The final pH typically ranges from 3.0 to 3.2, with lactic acid levels between 8 and 15 g/L. Bench tests reveal that Sourvisiae produces significantly more acidity than some competitors. As pH targets decrease, perceived tartness increases rapidly.

The finish of beers made with Sourvisiae can vary from very tart to intensely sour. At higher acid levels, the beer may approach an undrinkably sour taste, depending on the style and balance. This outcome aligns with the sensory expectations for a pure lactic profile.

Flavor neutrality is a key feature of Sourvisiae. It avoids the complexities of yeast, lactobacillus, and Brett found in mixed cultures. This results in a cleaner, more neutral flavor, ideal for recipes seeking a straightforward acid punch.

Choose the right strain for your style. Sourvisiae is best for bright, sharp lactic sour characters in kettle sours and Berliner Weisse. However, for fruit-forward or hop-driven sour ales, brewers might find it less characterful than Lachancea or mixed-culture ferments.

Key aroma: tangy, slightly fruity
Acidity range: high, pH ~3.0–3.2
Sensory expectations: clean lactic souring without Brett/LAB complexity

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Comparing Sourvisiae to other souring organisms and strains

Sourvisiae provides a more consistent acidification process compared to other methods. In Sourvisiae vs Lachancea comparisons, Sourvisiae reaches a terminal pH of 3.1–3.2. In contrast, Lachancea thermotolerans, like Philly Sour, finishes at 3.4–3.5. This difference results in Sourvisiae having a more pronounced acidity.

For those considering Philly Sour, it's important to note the flavor differences. Lachancea can introduce floral or fruity notes that complement dry hopping and fruit additions. Sourvisiae, on the other hand, offers a cleaner sour taste that focuses on tartness without the funk of Brett.

When comparing Sourvisiae to LAB, the operational risks change. Lactobacillus kettle souring produces a classic lactic flavor and a wide range of acids, depending on the strain. It requires strict handling and sanitation to prevent contamination. Sourvisiae, however, reduces these risks by not introducing a separate bacterial culture and typically shortening the process time.

Comparing Sourvisiae to Brettanomyces and mixed cultures highlights different goals. Brett and mixed yeasts create complex, funky, and evolving flavors. Sourvisiae, engineered to avoid Brett-like metabolites, offers a more consistent, cleaner sour taste that doesn't require extended aging.

Predictability: Sourvisiae provides consistent acidification and timing.
Flavor spectrum: Lachancea and Brett offer more complexity for certain styles.
Operational control: Sourvisiae lowers contamination risk versus LAB kettle souring.

The choice between organisms depends on the recipe and market goals. For quick, consistent tartness, Sourvisiae is ideal. For complex fruit, hop interactions, or barrel-aged funk, Lachancea, LAB, or Brett blends might be better. Each choice has its own trade-offs in flavor, process complexity, and aging time.

Recipe and process adjustments for best results

Creating a successful sour beer recipe hinges on achieving balance. Aim for a final pH of 3.0–3.2 with Lallemand Sourvisiae. Then, adjust the malt and adjuncts to counteract the acidity.

Consider the mash thickness and specialty malts to enhance dextrins and body. A thinner mash can increase perceived tartness. On the other hand, a thicker mash or the use of Munich and Vienna malts can soften the acidity in the final beer.

Hop management is crucial for acid production and flavor. Standard hopping is suitable for single-step souring. However, many brewers prefer low-bitterness kettle sours to highlight the tartness. It's wise to limit late bittering hops to avoid hindering microbial activity.

Fruit and dry hopping complement Sourvisiae's clean profile. If your test batches show muted fruit character due to acidity, reduce the fruit quantities. Adjust the additions in the kettle or fermenter to achieve the perfect balance for each fruit type.

Pitching strategy: follow Lallemand’s recommendation of 2.5–5 million cells/mL to ensure steady acidification and attenuation.
Under-pitching risks incomplete souring and lower attenuation, so avoid severe cell shortages.
Use Sourvisiae for single-step souring and fermentation to shorten process time and simplify control.

Avoid co-pitching fast-growing ale strains unless you plan to blend flavors. If repitching, monitor population ratios to keep Sourvisiae dominant and productive. These adjustments protect acid production and flavor consistency.

Small-scale test batches are essential for refining hops, fruit, and mash bills. Track pH and gravity through fermentation, then tweak the recipe for the next run. Gradual changes lead to reliable improvements in sour beer recipe outcomes.

Quality control and lab techniques for breweries

Establish a consistent QC routine for Sourvisiae that blends straightforward lab tests with practical brewery practices. Monitor viability and pitch rates before each batch to maintain consistent performance.

Employ a hemocytometer with trypan blue or an automated counter for precise viable cell counts. Target 2.5–5 million viable cells per mL, based on the recipe and wort gravity.

Regular yeast plating is crucial for detecting contamination and tracking population changes during repitch cycles. Plate samples at regular intervals and compare them to baseline plates.

Opt for selective media like chalk-wort agar to differentiate acid producers. On chalk-wort agar with 0.1% chalk, acid-producing colonies create clear halos. This accelerates the screening of mixed cultures.

Run short growth curve tests when competition is suspected; measure generation times to compare isolates.
Document colony morphology and record plates with dated photos for trend analysis.

pH monitoring is vital throughout fermentation. Log pH at transfer, mid-ferment, and terminal points to detect unexpected shifts.

Quantify lactic acid when more detail is needed. Use HPLC or validated colorimetric kits to measure concentrations, which commonly fall in the 8–15 g/L range for this strain.

Include storage checks in QC for Sourvisiae. Inspect dry pack vacuum seals and expiry dates. Do not use packs that show loss of vacuum or long air exposure.

Standardize sampling points and labeling for repeatable yeast plating results.
Calibrate cell counters and pH meters monthly to preserve data integrity.
Keep a logbook tying viability, pH monitoring, and plating to sensory and fermentation outcomes.

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Regulatory, safety, and labeling notes for US brewers

Lallemand states that Sourvisiae is Generally Recognized as Safe in the United States. The packaging and technical sheets highlight FDA GRAS determinations and standard safety classifications for food-grade yeast.

GRAS Sourvisiae is a bioengineered strain with a single LDH gene insertion. Brewers need to consider this when sourcing. It's also important to understand how GMO ingredients might impact consumer perception and sales messaging.

There is no universal U.S. law requiring GMO labeling at the ingredient level for beer. Yet, many companies choose transparency in their marketing or avoid discussing modifications. It's crucial to consult regulatory counsel when crafting label claims to ensure compliance with federal and state regulations.

When handling dry Sourvisiae, follow standard brewery safety and hygiene practices. Store unopened dry packs at under 4°C when advised. Avoid inhaling powdered yeast and follow the supplier's MSDS for spill control and PPE guidance.

The risk of cross-contamination increases with genetically modified, acid-producing organisms. Use separate tanks, maintain dedicated cleaning regimens, and schedule clearly to minimize the risk of unintended transfer to non-sour or neutral ferments.

Document storage, handling, and cleaning procedures specific to GRAS Sourvisiae.
Train staff on PPE, inhalation avoidance, and safe rehydration techniques.
Keep labeling decisions and marketing language consistent with counsel advice on GMO labeling.

Keep records of supplier statements about FDA GRAS status and retain batch documentation for traceability. Clear procedures protect product quality and support swift response if regulatory questions arise.

Where to buy, product formats, and vendor details

Sourvisiae is available through well-established brewing channels. You can find it at major distributors and retail suppliers across the United States. Before ordering in bulk, check with local wholesale suppliers for stock and prices.

Lallemand markets this strain under the LalBrew Sourvisiae label. It comes in dry active yeast, packaged in vacuum-sealed packs. Options include small homebrew sachets and larger 500 g commercial packs. The yeast typically has 93 to 97 percent solids and a viability of at least 5 x 10^9 CFU per gram.

White Labs also offers the strain, known as White Labs Sourvisiae (part no WLDSOURVISIAE), through its partnership with Lallemand. This partnership broadens the availability of Sourvisiae, making it easier for breweries to source from trusted suppliers and lab partners.

It's crucial to handle packs carefully upon receipt. Store them refrigerated at below 4°C (39°F). Do not use packs that have lost vacuum. Once opened, reseal and use within the recommended timeframe to maintain viability and performance.

Check the expiry and lot code printed on each pack before use.
Verify percent solids and viability if technical details are required for brewing records.
Contact brewing@lallemand.com for technical support or questions about LalBrew Sourvisiae performance.

When sourcing, compare lead times and minimum order quantities among Sourvisiae vendors. Availability in the U.S. is extensive, thanks to Lallemand’s distribution network and White Labs partner channels. For consistent supply, establish a relationship with a preferred distributor and ensure cold-chain handling during transit.

Conclusion

Sourvisiae review conclusion: Lallemand Sourvisiae Yeast is a bioengineered solution for brewers seeking reliable souring. It offers predictable acidification, achieving pH levels of 3.0–3.2. This process is faster than traditional methods, reducing turnaround times significantly.

Its consistent acid production across various pitches and gravities makes it ideal for controlled kettle sours and Berliner Weisse styles. This yeast ferments vigorously in 4–7 days at 20°C, with high flocculation. It excels in both craft and production settings due to its operational advantages.

However, it grows slower than common ale strains and can be outcompeted in mixed cultures or during serial repitches. Its sensory profile is intensely tart, with a somewhat neutral character compared to other sour organisms.

Is Sourvisiae right for my brewery? It's suitable when clean lactic notes and quick turnaround are essential. Avoid routine co-pitching with fast ale strains. For repitching, proceed with caution and maintain strict quality control.

Practical next steps include trialing at recommended pitch rates (2.5–5 million viable cells/mL). Monitor pH and lactic acid levels closely. Ensure separation to prevent contamination and evaluate sensory balance before scaling.

Lallemand Sourvisiae Yeast summary: It's a reliable tool for targeted souring, prioritizing predictability and speed. With proper handling and quality control, it streamlines production. However, it demands careful management for long-term reuse and mixed-culture work.