Research and analysis

Assessment report on an application for deliberate release of a genetically modified organism (GMO) for marketing purposes

Updated 3 August 2026

Applicant:

Lallemand UK Limited (Representing Danstar Ferment AG Switzerland)

Application:

To market Genetically Modified Saccharomyces cerevisiae for use as a food production aid in brewing. The product, termed Sourvisiae®, has been modified to produce lactic acid resulting in the production of sour-flavoured beer.

Ref: 26/GM/01

Summary

The Secretary of State has the powers conferred by Part VI of the Environmental Protection Act 1990, to consider an application to market a GMO. This includes the production of an assessment by reference to the regulatory requirements as set out in the Genetically Modified Organisms (Deliberate Release) Regulations 2002, Schedule 4. In producing this assessment, the Secretary of State sought advice from the Advisory Committee on Releases to the Environment to the Secretary of State under section 124 of the Environmental Protection Act 1990.

The Advisory Committee on Releases to the Environment (ACRE) is satisfied that the information provided by the applicant in accordance with the current regulations on the Deliberate Release of GMOs, demonstrates that the release of the GMO for marketing purposes has been fully assessed in relation to the risks of adverse effect on human health or the environment. ACRE therefore see no reason for the release for marketing purposes not to receive a positive assessment.

In producing this assessment, the Secretary of State is required to follow the format of Schedule 4 of the regulations and therefore is required to specify the conditions under which the GMO may be marketed. Advice from ACRE noted that the GMO would be expected to survive the brewing process to a degree and that therefore viable GMOs would be present in brewing waste and in the brewed beer. Therefore, both post-production removal from the beer is a stipulated condition of marketing and the post marketing environmental monitoring of brewing residual waste (both solid and liquid) is required to confirm the lack of persistence of the GMO to verify the negligible likelihood for release of the GMO from this waste.

Background

On 3 March 2026 Defra officially acknowledged receipt of an application from Lallemand UK Ltd to release a GMO for marketing purposes in accordance with Directive 2001/18/EC. The application included an environmental risk assessment relevant to the release under the proposed marketing purposes, along with a post marketing environmental monitoring plan, as required by the Directive.

The GMO is a genetically modified micro-organism (GMM), derived from a strain of Saccharomyces cerevisiae used in the commercial brewing industry for more than 20 years. This strain was genetically modified through homologous recombination to carry the lactate dehydrogenase (ldhA) gene from Rhizopus oryzae. The applicant has conducted detailed analyses of the GMM to reveal the genomic location, copy number and stability of the inserted ldhA gene.

The safety profile of the GMM compared to the wild type S. cerevisiae is considered in depth within the application, in relation to the intended use of the product when marketed under the trade name Sourvisiae®. The intended use is that of a fermentation/processing aid in the production of beer and related alcoholic beverages. It is intended to provide controlled lactic acid production during fermentation.

There was evidence that despite the brewing process resulting in lactic acid production, which is toxic for the GMM, residual levels of viable cells would be present in the beer (as seen in that produced by the wild type strain) and therefore filtration and/or pasteurisation as routinely carried out in commercial brewing will be stipulated under the terms of marketing to remove surviving GMMs.

Spent brewer’s yeast is routinely disposed of via municipal waste routes, which is also proposed for the spent GMM. The applicant therefore has conducted extensive literature reviews on the survivability and persistence of both wild type and genetically modified yeasts. They conclude that industrial strains of yeasts are very poorly suited to survive in nutrient-depleted environments and that the GMM therefore presents negligible environmental risk when so disposed of. The applicant’s environmental impact assessment (EIA) arrives at a similar conclusion, namely that the GMM will have negligible impact.

The characteristics of the recipient microorganism

S. cerevisiae, is a species classified as Hazard Group 1 under UK Advisory Committee on Dangerous Pathogens (ACDP) guidance, meaning it is unlikely to cause human disease. This classification aligns with EFSA’s Qualified Presumption of Safety (QPS) status for S. cerevisiae, which recognizes its long history of safe use in food and feed applications.

The genetically modified micro-organism, product name Sourvisiae®, is a strain of Saccharomyces cerevisiae, identified by the code: M16141. The parent strain was modified through homologous recombination to carry the lactate dehydrogenase (ldhA) gene from Rhizopus oryzae. The recipient S. cerevisiae strain has been used in the commercial brewing industry for more than 20 years and was therefore selected for modification due to its robust fermentation performance and safety profile.

The donor organism, Rhizopus oryzae, is taxonomically distant from S. cerevisiae, belonging to the Mucoromycota phylum (formerly grouped under Zygomycota), whereas S. cerevisiae is in the Ascomycota phylum. Despite this phylogenetic distance, the ldhA gene was chosen due to its well-characterised metabolic function and history of safe use of lactic acid in food applications. Furthermore, R. oryzae is a micro-organism that is used industrially and well-characterised for lactic acid production.

Description of the genetic modification made to the recipient microorganism

The Secretary of State sought scientific advice from ACRE on the method employed to produce this GMO. The modified S. cerevisiae, strain M16141, was obtained via standard molecular biological techniques utilising small circular genetic elements called plasmids, to obtain a transformant LDH-expressing strain. With the plasmid being cured during the subsequent plating and passaging of the transformant. This removal was confirmed by polymerase chain reaction (PCR) genotyping, dilution plating onto selective medium, along with whole genome sequencing to confirm that both no plasmid backbone was present; and the intended LDH expression cassette was properly integrated. In addition, a diagnostic, quantitative polymerase chain reaction (qPCR) was developed that revealed there were 4 copies of the ldhA gene were present in M16141. This is consistent with the strain and its parent being tetraploid (having four copies of each chromosome).

ACRE were content that the applicant had demonstrated that this plasmid was only used as a co-transformation aid, and no plasmid genetic material was integrated into the cell. Further, the GMM, Strain M16141, was shown to be genetically stable over 100 generations, by analysis of Genomic DNA by PCR to confirm stability of the inserted transgene. Therefore, the applicant has produced sufficient data from these genetic analyses, on the genetic stability of the GMM, including the absence of any introduced mobile genetic elements.

An identification of any known risks of damage to the environment resulting from the release into the environment of the recipient non-modified organism

S. cerevisiae, is a species classified as Hazard Group 1 under UK Advisory Committee on Dangerous Pathogens (ACDP) guidance, meaning it is unlikely to cause human disease. This classification aligns with EFSA’s Qualified Presumption of Safety (QPS) status for S. cerevisiae, which recognizes its long history of safe use in food and feed applications.

S. cerevisiae does not have a host range nor act on any target organism, neither does it prey upon or parasitize other organisms. There are also on no symbiotic relationships reported. The strains of the yeast do not form mutualistic associations with plants, animals, or other microorganisms.

This yeast competes poorly with native microorganisms in soil and aquatic ecosystems. Common competitors such as lactic acid bacteria can inhibit yeast growth through organic acid production. The applicant reports that a literature review found no significant parasitic interactions for S. cerevisiae, and it does not require a host for survival.

S. cerevisiae competes with other microorganisms under fermentation conditions but is not expected to outcompete them due to reduced fitness outside of beer wort environments. The applicant includes data from papers specifically looking at the survival of industrial yeast strains in the environment surrounding vineyards and other industrial sites. From this data it can be concluded that industrial yeast strains have been adapted to controlled, optimised and nutrient rich environments and therefore this significantly compromises their survival under natural conditions where such factors are uncontrolled, highly variable and limited.

The subject of horizontal gene transfer (HGT) is frequently discussed with regards to the environmental persistence of microorganisms, or their particular genetic traits. The potential for transfer of integrated genetic material from one strain to another in S. cerevisiae is very low or negligible given that as noted by the applicant, HGT has rarely been reported in yeast.

Assessment of whether the genetic modification has been characterised sufficiently for the purpose of evaluating any risks of damage to the environment

Sourvisiae® underwent pathogenicity screening as part of its safety evaluation to confirm its classification as a Hazard Group 1 organism. The screening demonstrated that the strain did not exhibit pathogenic traits, cause mortality, or produce signs of toxicity in the test systems employed. The applicant therefore assesses that the human health hazard of S. cerevisiae strain Sourvisiae® is non-existent to low. They have based this on considerations of history of use of the wild-type strain; the nature of the genetic modifications; biology of the donor organism and the inserted genetic material, and species background and occupational exposure.

There are no reports of allergenicity associated with LDH from R. oryzae, and the application dossier confirms that Sourvisiae® does not produce harmful metabolites and meets strict contaminant specifications. No additional allergenic risk beyond conventional brewing yeast was identified. In addition, the strain will be used under controlled conditions including during its preparation for introduction to the required fermentation during beer brewing. Therefore, the likelihood of the conducive conditions to elicit allergenic reaction can be considered as negligible.

Lactic acid production by strain M16141 was confirmed with high performance liquid chromatography (HPLC) analysis, including for both the first generation and the 100-passage strain. This analysis revealed that the latter strain produced equivalent lactic acid to that of the pre-passage strain.

By consideration of the applicant’s analysis of the GMM’s phenotype, the data supported a conclusion that the presence of the gene did not change the physiology of the yeast in any way that could foreseeably change its behaviour through any potential competitive advantage arising from the transgene within in the (wider) environment. This is partly because there are significant populations of organisms expressing LDH already present in the environment. To this it should also be added that wild type S cerevisiae expresses mitochondrial LDH; if there was any possibility that a highly adapted environmental organism could arise by changing the location or expression of these, it is reasonable to expect this to have already happened. 

This assessment is content that the applicant has provided sufficient data revealing that the engineered M16141 strain exhibited equivalent, or slightly greater, sensitivity to clinical antibiotics compared to the other strains tested. However, the genetic modification has resulted in M16141 becoming insensitive to the anti- metabolite 5-Fluorocytosine (5-FC).  Nonetheless, this did not represent any risk as the drug based on this antimetabolite is not used uniquely to treat fungal infections because spontaneous resistance to it occurs at a high rate. Further, this insensitivity also results in the GMM being unable to grow on media where Cytosine is the sole carbon source, limiting its growth in nutrient-depleted environments.

Assessment of risks to the environment that may arise from the release of the GMM compared to the donor

Defra considered this taking advice from ACRE and were content that the applicant had conducted sufficient survival studies and literature searches to indicate no significant difference in survivability between Sourvisiae® and unmodified parental strains under environmental conditions.

Furthermore, LDH activity without a steady supply of wort sugars is expected to reduce fitness of the modified strain in open environments. Therefore, we are content to assess that the overall risk is negligible or non-existent for conservation and sustainable use of biodiversity, because Sourvisiae® behaves like the parental brewing yeast in open environments, has no selective advantage outside brewing conditions, and lacks retained antibiotic resistance markers.

Further the GM strain does not possess mobile genetic elements, plasmid backbone sequences, and the demonstrated chromosomal integration of the transgene limits genetic transfer. Those organisms with any risk of undergoing HGT with the GMM are considered in detail by the applicant along with the subject of any known or predicted involvement of the GMM in biogeochemical processes. Defra’s assessment agrees with the application’s summary that there was negligible likelihood of HGT and that the GMM was not expected to have any effect on biogeochemical processes beyond that of the wild type, namely a minimal one.

The well-characterised nature of the recipient microorganism informed the assessment on whether the GMM possesses any competitive advantage over the wild type, which was to conclude that apart from the ability to efficiently produce lactic acid during the ethanol producing fermentation process, there is no evidence for any such advantage in an environmental release.

Defra therefore assesses that the GMM is no more likely to survive and persist in the environment than the wild type strain, as the GMM does not possess traits that enhance survival in natural environments. Its fitness is reduced outside wort due to reliance on fermentable sugars and sensitivity to abiotic stressors such as temperature extremes, UV exposure, and nutrient limitation. Microcosm studies referenced in the submission confirm rapid viability loss in soil and water.

Therefore, Sourvisiae® is not expected to proliferate in the natural environment. The spent brewer’s yeast is typically disposed of as municipal waste, the expected maximum number of cells in this is 0.5-1 x 106 cells/ml.  However, as discussed earlier, any yeast residue that may be sent to landfill is not expected to proliferate as most landfill conditions are low in moisture and anaerobic (oxygen-poor) due to physical compaction of the solid waste and therefore do not provide an optimal environment for yeasts generally or other microbes to thrive.

Wastewater may be discharged in the publicly owned treatment works (or otherwise as regulations permit). The yeast in liquid waste is anticipated to be inactivated. These measures are consistent with industry best practices.

Therefore, ACRE concluded that as wastewater is not always fully treated, then their advice should take the variability of UK wastewater treatment into account, which therefore would be that there should be more clarity about the brewery-level WW pretreatment and and/or monitoring of wastewater that is required when this strain has been used.

The applicant found that no adverse interactions with non-target organisms, including competitors, prey, hosts, symbionts, predators, parasites, or pathogens, were identified in the literature. The yeast is not naturally adapted to ecological niches and is unlikely to persist or disseminate in soil or aquatic environments. Therefore, the risk of impact on either target or non-target ecosystems is considered negligible under the proposed use conditions.

The applicant has assessed that due to the low potential hazard and low potential exposure, the environmental risk is negligible, based on its biological characteristics, lack of competitive advantage outside brewing conditions, and standard containment measures in breweries. The applicant further concludes that the overall environmental impact of the release of the GMM is expected to be negligible.

Proposed marketing and further considerations (including supply, use and labelling)

The commercial yeast Sourvisiae®, will be imported into England and sold to customers for use as a fermentation or processing aid to produce alcohol and to provide (sour) flavour in beer production. Commercial or craft breweries will receive it as a dry product in 500g vacuum package that is clearly labelled as being genetically engineered; an example label was included with the application. ACRE considered this label to be clear and sufficiently detailed.

Sourvisiae® is intended to be used in controlled brewing environments such as commercial breweries and pilot-scale brewing facilities using standard brewing practices. The organism will be handled under standard brewing conditions ensuring it is confined within fermentation vessels.

Of relevance to this marketing application is that the focus of beer production is on hygiene and microbial containment to produce a suitable product. Also noted within the application is the following on control measures: Breweries implement food safety plans that implement standard containment practices, this (can) include closed fermentation systems, controlled waste handling, and clean-in-place (CIP) sanitation protocols. In addition, they must also adhere to the food hygiene regulations which provides for implementation, control and verification of measures in place to assure food safety.

The recommended use of the product is to add to a fermentation tank (or vessel) the GM yeast product (from a 500g bag as supplied) at the recommended pitching rate of 50 to 100 g/hectolitre (hL, 1hL = 100L) to achieve a minimum of 2.5 to 5 million cells/mL at the beginning of the beer fermentation. Most of the UK’s breweries are small, local operations, with 94% producing less than 15,000 hL of beer per year. Therefore, it is expected that most craft breweries will have fermentation tanks that are less than 1,000 barrels (117.4 L or 1.17 hL) in size.

At the end of the fermentation, the waste yeast is separated from the (green) beer, which can typically be done by flocculation, sedimentation and/or centrifugation (in breweries). This spent brewers’ yeast is typically disposed of as municipal waste. Additionally, there may be spent yeast residue in the brewery wastewater which is discharged in the publicly owned treatment works.

Typically, in the commercial production of alcoholic beers, the product is pasteurized and filtered after maturation, which inactivates and removes the remaining yeast in the final product. Filtration helps stabilize beer and gives it a polished, clear appearance. It can also remove components, such as dead yeast, that otherwise would eventually make the beer unpalatable.

The applicant states that the finished product beer is expected to have 1 x 10^6 cells/ml, therefore without treatment consumers would be exposed to some of it, and it would enter the environment in any brewing waste. Therefore, ACRE advised that to ensure that the product does not require subsequent authorisation under the GM food regulations there should be a clearly stated requirement for breweries to pasteurise and/or filter out the GM yeast from the finished product beer.

Conclusion

Post marketing environmental monitoring plan: case specific and general surveillance

The PMEM described by the applicant detailed that an initial 18-month period of case-specific monitoring was proposed to confirm inactivation of the GMM in brewery waste materials along with general surveillance that is normally implemented as part of the food production process. Reporting plans along with handling to ensure questions of commercial confidentiality are dealt with were set out, along with meeting the requirements to review and adapt these plans as any need was highlighted during the marketing consent period (of 10 years).

The requirements of food production systems and supply of processing aids such as this GMM, ensure that full traceability is in place as a legal requirement. The applicant intends to ensure the PMEM requirements are built into any commercial contract under which the GMM is supplied.