New substances: risk assessment summary 21962

Overview

Notified organism: Saccharomyces species strain MBG 5318

Schedule of the New Substances Notification Regulations (Organisms) [NSNR(Organisms)]: Schedule 1 - Information Required in Respect of Micro-organisms

Organism type: Yeast

Use: Manufacture of MBG 5318 in Canada for use in production of ethanol

Anticipated quantity: confidential and not for disclosure

Assessment level of concern:

• Human health hazard: Low
• Human exposure: Low
• Environmental hazard: Low
• Environmental exposure: Low

Assessment conclusion under section 64 of the Canadian Environmental Protection Act, 1999 (CEPA): Low risk, not suspected to be toxic

Category: Added to the Domestic Substances List on November 19, 2025 under the name Saccharomyces species strain 5318

Recommended action: None

Waiver: Requested for information on data from tests conducted to determine the effects of the micro-organism on aquatic vertebrate species likely to be exposed to it (subparagraph 5(a)(i) of Schedule 1 of the NSNR(Organisms)) under CEPA, paragraph 106(8)(a)

Synopsis

Saccharomyces species strain MBG 5318 is classified as a Risk Group 1 (RG1) animal and human pathogen by the Public Health Agency of Canada (PHAC), meaning it presents a low individual and community risk.

Strain MBG 5318 was notified for its manufacture and use in bioethanol production. Other potential uses of strain MBG 5318 include:

• consumer sectors
• industrial sectors
• commercial sectors
• agricultural sectors

There is no evidence to suggest a potential risk of adverse environmental effects at the exposure levels predicted to the environment from the intended use in bioethanol production, or from other potential uses. Due to the low potential for hazard and the low potential for exposure to the environment, strain MBG 5318 is not suspected to meet criteria in paragraphs 64(a) or (b) of CEPA.

There is no evidence to suggest a risk of adverse human health effects at the exposure levels predicted for the general population in Canada from the use of this organism. Owing to the low potential for hazard and the low potential for exposure to the general population in Canada, Saccharomyces species strain MBG 5318 is not suspected to meet criteria in paragraph 64(c) of CEPA.

A waiver request for information element 5(a)(i) of Schedule 1 of the NSNR(Organisms) for the data from tests conducted on aquatic vertebrates was granted. Information gathered from such tests to determine whether the organism is toxic or capable of becoming toxic on aquatic vertebrates is not necessary given that strain MBG 5318 is an unmodified yeast belonging to a species with a long history of safe use in the aquaculture industry as a feed supplement.

Background information

Saccharomyces species strain MBG 5318 is a yeast derived by mass mating of several commercial strains of Saccharomyces. All parental strains are commonly used in the baking and winery industries. Saccharomyces species strain MBG 5318 was selected for its ability to efficiently ferment corn mashes and yield increased ethanol production. The strain was originally isolated in Australia and was shipped to the notifier’s containment facility in 2023. MBG 5318 has been notified by a customer of the notifier under two previous Schedule 2 notifications for use in contained ethanol production facilities. The current notification is for its manufacture and use in bioethanol facilities.

Hazard assessment

The environmental hazard potential of Saccharomyces species strain MBG 5318 is determined to be low because:

• there is limited history of safe use for the notified strain MBG 5318 in two contained facilities in Canada
  • MBG 5318 is the parental organism for several genetically modified strains of Saccharomyces species such as YS344-D1, notified and assessed under NSN 21842 (Schedule 2)
  • YS344-D1 has been safely manufactured, imported and used in a contained facility with no reports of adverse effects since 2024
• test data was provided for MeJi797 and yMHCT484, two genetically modified surrogate strains of Saccharomyces species with similar lineage to the notified strain
  • no adverse effects were observed in terrestrial plants or in terrestrial or aquatic invertebrates
  • the available information suggests that the notified organism is not harmful in these environmental compartments
• surrogate data on genetically modified strains Saccharomyces species MeJi797 and yMHCT484 were provided to determine the effects on terrestrial vertebrates using a mouse model
  • there was no evidence of proliferation or pathogenicity, and no mortalities during the 22-day test period
  • there is a small likelihood that an acute infection may occur, however, any potential infection is likely to be rare and not lethal
• the information provided by the notifier and the New Substances (NS) program’s search of the scientific literature yielded no results for potential adverse effects (pathogenicity or toxicity) to aquatic vertebrates for Saccharomyces species
  • Saccharomyces species have a long history of safe use as a supplement in aquatic vertebrate feed preparations, providing increased feed digestibility, increased growth performance and immune stimulation
  • taken together, the available information indicates that the strain MBG5318 is unlikely to result in adverse effects in aquatic vertebrates
• the potential transfer of genetic material from the strain MBG 5318 to other Saccharomyces species is very low, given that horizontal gene transfer has rarely been reported in yeast
  • in addition, there is no targeted insertion of genetic material, and the strain has been generated solely through mass mating, further lessening the possibility of any horizontal gene transfer

The human hazard potential of Saccharomyces species strain MBG 5318 is determined to be low because:

• although no deliberate genetic modification was involved in the generation of strain MBG 5318, it was produced by mass mating of several commercial strains of Saccharomyces used in baking and wine industries, none of which have been reported to cause any adverse human health effects
• published scientific literature indicates that certain Saccharomyces strains have a low potential for allergenicity
  • strain MBG 5318 is derived from strains used in the baking and wine industries and therefore expected to have similar allergenicity profile
  • the NS program’s search of the scientific literature did not identify documented allergic reaction cases specifically associated with parental strains
• strain MBG 5318 was classified by PHAC as a RG1 human pathogen and RG1 animal pathogen for terrestrial vertebrates under the Human Pathogens and Toxins Act
• several putative virulence traits have been attributed to certain probiotic and clinical strains of Saccharomyces species such as growth at high temperatures, pseudohyphal growth and high protease and phospholipase activity
  • data provided by the notifier indicates that strain MBG 5318 is not invasive, does not produce phospholipase or protease, and did not show significant growth after 4 days at 42°C
  • this property alone (growth at 42°C) is not associated with strains implicated in clinical infections in humans
• pathogenicity studies conducted using two genetically modified surrogate strains (MeJi797 and yMHCT484) on BALB/C mice given a single intravenous injection of at least 10₇ CFU did result in clinical signs that could be considered as an acute response to infection
  • however, there was no evidence of proliferation of the surrogate strains and there were no mortalities over the 22-day study period
  • in addition, no tissue abnormalities were observed during necropsy following the study period
  • the effects observed for the surrogate strains are similar to those reported in literature for avirulent baking or wine strains of Saccharomyces
• Saccharomyces species have a wide distribution in nature and a long history of use especially in baking and alcohol production
  • reports of infections from wild-type Saccharomyces strains in healthy individuals are rare, but there are documented cases of Saccharomyces infections predominantly in immunocompromised individuals or those with pre-existing medical conditions
  • these infections are treated using antifungal therapy
• strain MBG 5318 is sensitive to clinically relevant antifungal agents. Treatments are therefore available in the unlikely event of infections caused by strain MBG 5318
• furthermore, the NS program’s modelling predicted that there would be no human health burden (measured as daily-adjusted life years (DALYs)) resulting from those predicted exposure levels from both the notified and potential uses

Hazards related to micro-organisms used in the workplace should be classified accordingly under the Workplace Hazardous Materials Information System (WHMIS)^{Footnote 1} .

Exposure assessment

The environmental exposure potential of Saccharomyces species strain MBG 5318 is determined to be low because:

• the notified organism is intended for use in ethanol production and will be manufactured in a contained facility that meets the requirements of Appendix K-III of the NIH Guidelines (Biosafety level 1-Large Scale), ensuring adequate monitoring and treatment of all solid, liquid and gaseous wastes
• the potential locations of the facilities where the yeasts can be used are widespread throughout Canada
• taking into account the proposed use and the procedures in place to limit any potential release, as well as effective treatments to inactivate the notified organism, no significant environmental release is expected that could result in exposure to the notified microorganism
• in the unlikely event of release from ethanol production facilities, the plants and animals that could be exposed are those in the immediate area surrounding the facility
  • as indicated by the notifier, little to no viable organisms will remain in the spent supernatant
  • if this material is released untreated to the municipal sewer or an anaerobic digestion facility the level of dilution will result in a concentration of organisms that is not expected to negatively affect the environment
  • significant outgrowth of the organisms would not be expected to occur
• a search of the public domain (literature and patents) revealed a number of consumer, commercial and industrial applications for other strains of Saccharomyces species, including bioremediation, wastewater treatment, decomposition of agricultural and food processing wastes or as a deodorizer in municipal landfills
  • however, strain MBG 5318 is proprietary to the notifier and given the specific nature of the characteristics achieved through mass mating, it is unlikely that the notified strain would have any potential uses other than in bioethanol production
  • should strain MBG 5318 be used in these other applications, the estimated concentrations seen in a worst-case scenario would not reach a level of environmental concern
• existing oversight by provincial and local governments would minimize the releases of hazardous or biological wastes into the environment and limit liquid discharges to sewers and sewage works

The indirect human exposure potential of Saccharomyces species strain MBG 5318 is determined to be low because:

• strain MBG 5318 will be manufactured within a single contained facility in accordance with the requirements of Appendix K-III of the NIH Guidelines (Biosafety Level 1 ‐ Large Scale), whereas any subsequent bioethanol production facilities may operate under Good Large-Scale Practice (GLSP)
• the fermentation broth will be inactivated prior to the disposal
• a closed system will be maintained throughout the initial manufacturing process and subsequent bioethanol production
  • all manufacturing plant personnel should have adequate training, and standard operating procedures should be in place to deal with any accidental spills or loss of culture
• releases of viable strain MBG 5318 into the environment are expected to be negligible from the manufacturing and subsequent bioethanol production facilities since all liquid, solid, and gaseous wastes containing the notified micro-organism will be inactivated prior to spent supernatant disposal or release into the environment, and containment measures are in place in the event of a spill
  • there will be no live organisms in the produced bioethanol
• should there be a release into the environment, favourable conditions are possible for survival and establishment
  • however, Saccharomyces species are generally not known to persist in receiving environments or outcompete native strains
• should the containment level change to GLSP, no significant change in human exposure to strain MBG 5318 is expected since the GLSP level of containment requires discharges containing viable organisms will be handled in accordance with applicable provincial regulations and municipal by-laws
• like other Saccharomyces strains, strain MBG 5318 can potentially be used in products such as food additives, pharmaceuticals, human biologics, veterinary drugs, cosmetics and natural health products, which are regulated under the Food and Drugs Act
  • indirect human health effects from these uses are expected to be low compared to the direct exposure to live organism from such uses
• the notifier intends to use the inactivated byproducts from the ethanol production as Distillers Grains, which may be subject to other Acts and Regulations
• in addition, the strain MBG 5318 can also be used in bioremediation, waste water treatment, decomposition of agricultural and food processing wastes or as deodorizer in municipal land fills
  • environmental release concentrations of strain MBG 5318 to which humans may be exposed to accidentally were calculated using the NS program’s modelling based on three potential release scenarios at the highest concentration from the manufacturing facility
  • in all scenarios, the concentration at which humans would be exposed to the strain MBG 5318 from environmental media is lower than the concentration at the point of introduction in case of accidental release

Risk characterization

Owing to the low potential hazard and the low potential exposure, the environmental risk posed by Saccharomyces species strain MBG 5318 for the notified manufacture and use in ethanol production or for other potential uses is determined to be low.

Owing to the low potential hazard and the low potential exposure, to the general population in Canada, the human health risk associated with the use of Saccharomyces species strain MBG 5318 in ethanol production and other potential uses including those in consumer, industrial, commercial and agricultural sectors is determined to be low.

Risk assessment conclusion

There is no evidence to suggest risk of adverse environmental effects at the exposure levels predicted to the environment from manufacture and use of the notified strain MBG 5318 in ethanol production or for any other potential use. The risk to the environment associated with Saccharomyces species strain MBG 5318 is not suspected to meet criteria in paragraphs 64(a) or (b) of CEPA. No further action is recommended.

Similarly, there is no evidence to suggest a risk of adverse human health effects at the exposure levels predicted to the general population in Canada from the notified use of Saccharomyces species strain MBG 5318 for ethanol production and potential uses including those in consumer, industrial, commercial and agricultural sectors. The risk to human health associated with Saccharomyces species strain MBG 5318 is not suspected to meet criteria in paragraph 64(c) of CEPA. No further action is recommended.