New substances: risk assessment summary 18544

Official title: Risk assessment summary for NSN 18544: Saccharomyces cerevisiae, a genetically modified strain, for industrial production of bioethanol

Introduction

Under the Canadian Environmental Protection Act, 1999 (CEPA), animate products of biotechnology (i.e. “living organisms”) not listed on the Domestic Substances List (DSL) are considered “new” to Canada. Information and data prescribed by the New Substances Notification Regulations (Organisms) [NSNR(O)] must be submitted before manufacture or import takes place, and the assessment is conducted by Environment and Climate Change Canada (ECCC) and Health Canada (HC). In other words, the Government of Canada must be notified before new living organisms are manufactured in or imported into Canada, and must assess their potential to harm human health and the environment.

A genetically modified strain of Saccharomyces cerevisiae, (hereafter, the notified organism) was notified for industrial production of bioethanol (manufacture) and was assessed according to the requirements of Schedule 1 of the NSNR(O), which applies to the manufacture or import of new micro-organisms for introduction anywhere in Canada.

Regulatory decision

The notified organism is considered not to be harmful to human health or the environment for the intended use in the industrial production of bioethanol. In addition, the notified organism is not anticipated to enter the environment in a quantity or under conditions that have or may have an immediate or long term harmful effect on the environment or its biological diversity, constitute a danger to the environment on which life depends or constitute or may constitute a danger in Canada to human life or health.

After 21 April 2016, the manufacture or import of this genetically modified strain of S. cerevisiae could proceed in Canada. This strain is eligible to be added to the Domestic Substances List but until such time that it is officially published in the Canada Gazette, it would still be considered a ‘new substance’ and subject to the NSNR(O).

However, because the notified organism could enter the environment in a quantity or under conditions that constitute or may constitute a danger in Canada to human life or health for potential uses that were not assessed, application of the significant new activity (SNAc) provisions in CEPA was recommended. The SNAc notice specifies additional information that must be provided by anyone wishing to manufacture, import or use the micro-organism for a significant new activity described in the notice. In this case, additional information is requested that will allow ECCC and HC to assess potential risks to immunocompromised individuals associated with new activities.

The SNAc Notice  for this notified organism was published in Canada Gazette, Part I on June 25, 2016.  Therefore, when it is added to the DSL, it would be indicated that a SNAc applies.

Background

The notified organism is a genetically modified yeast strain that is intended for use in the production of bioethanol. As a result of the modifications, the micro-organism is able to digest starch more efficiently resulting in higher yields of ethanol.

Hazard considerations

The environmental hazard potential of the notified organism is considered to be low for the following reasons:

• The parental strain has been used in industrial bioethanol production plants around the world without any reports of environmental harm.
• The gene modifications in the notified organism are well characterized and are considered to be stable in the micro-organism. There are no environmental hazards associated with these modifications.  In addition, the probability of any transfer of the introduced DNA from the notified organism to other organisms is expected to be minimal.
• Test data were provided by the notifier to determine the effects of the notified organism on terrestrial plants and invertebrates as well as aquatic invertebrates, while surrogate data were provided for aquatic plants and aquatic vertebrates (references provided by the notifier). The notified organism was not found to have any adverse effects except in aquatic invertebrates, where some adverse effects were observed on the reproduction rate of young adult aquatic crustaceans. However, these effects were seen at a concentration much higher than expected concentrations in the environment.
• Test data were also provided by the notifier to determine the effects of the notified organism in terrestrial vertebrates. Healthy rodents were given different doses of the micro-organism and the results indicated a small likelihood of infection if terrestrial vertebrates are exposed to significant concentrations of the notified organism. Any potential infection is likely to be rare and not lethal. Furthermore, the transmissibility of an infection to other individuals is unlikely and so adverse effects at the population level are not expected.
• In the event of infections in individual terrestrial vertebrates, effective antifungals for veterinary use are available.
• No other negative ecological effects were found in the literature for the notified strain or the species.

The human hazard potential of the notified organism is considered to be low for the general population and medium for immuno-compromised individuals, for the following reasons:

• The gene modifications in the notified organism are well characterized and are considered to be stable in the micro-organism.
• Expression of a certain enzyme resulting from the genetic modifications may increase the potential for the notified organism to cause allergic reactions.
• S. cerevisiae has long been associated with human activities, particularly with bread and alcoholic beverage production, yet infections in healthy individuals are rare. Where human infections to S. cerevisiae have been reported, the majority are in individuals rendered vulnerable by weakened immunity or underlying diseases or medical conditions.
• The notified organism shares only one of the traits associated with pathogenic strains: the ability to grow at human body temperature.  Because its parental strain can grow at temperatures close to or above human body temperature (i.e. ≥ 37°C), the notified organism is also likely to do so. However, like its parent, the notified organism is unlikely to undergo filamentous growth under low nitrogen conditions or excrete the enzyme phospholipase. The absence of the latter two characteristics is an indication that the micro-organism is less likely to be harmful in humans.
• In vivo pathogenicity testing of the notified strain with an immuno-competent rodent model demonstrated infectivity (as measured by clearance from various organs and tissues) more similar to that observed in a clinical strain than that observed in a non-pathogenic strain.  This indicates that the notified strain may have the potential to cause infection, particularly in immune-compromised individuals.
• In the unlikely event of infection with the notified organism, effective antifungal drugs are available.

Exposure considerations

The environmental exposure potential of the notified organism for bioethanol production in Canada is considered to be low-medium for the following reasons:

• A large amount of yeast biomass is expected to be produced in each fermentation cycle at bioethanol facilities. However, inactivation data for surrogate strains were provided indicating that the bulk of this biomass would be significantly inactivated during the ethanol extraction (distillation) process. Thus, any remaining yeast composing the bulk of the waste stream would be inactive and live cells released in air emissions and liquid wastes will not be in significant numbers.
• The few live cells that do reach the environment are expected to remain near the site of release because the potential for further reproduction and distribution in the environment is low.

The human exposure potential of the notified organism for bioethanol production and manufacture in Canada is considered to be low-medium for the following reasons:

• Current bioethanol production facilities are primarily located in industrial sections of small towns and not near residential areas.
• The majority of live organisms will be harvested, and the number of live organisms released in liquid and solid wastes is estimated to be low.

Estimated exposure from other potential uses

Since this strain has been optimized for use in a fermentation facility, the environmental and human exposure potential are both likely to remain the same for other potential uses of the notified organism such as in contained production of enzymes and biochemicals and in research and development activities. However, exposure could increase following listing of the notified organism on the DSL, or if used in other (not contained) activities such as a cleaning agent for ponds and aquariums, as a feed additive to reduce odour from animal waste products or in bedding materials for small animals and pets.  For activities not covered by an Act and Regulation listed in Schedule 4 of CEPA, users would have to comply with SNAc 18544.

Risk assessment conclusion

Risk is typically described as the probability of an adverse effect occurring based on hazards and a particular scenario of exposure (Environment Canada and Health Canada, 2011). Different exposure scenarios can be described based on intended and any potential uses. In the present case, the micro-organism will be used for the industrial production of bioethanol in a fermentation facility.

Given the low potential environmental hazard, the environmental risk associated with the low-medium potential environmental exposure from use of the notified organism used for bioethanol production is considered low.

Given the low potential human health hazard to healthy individuals and the medium potential hazard to immune-compromised individuals, the human health risk associated with the low-medium potential human exposure from the use of the notified organism for bioethanol production and manufacture is considered low-medium. Potential uses in bioremediation, for production of enzymes and biochemicals or as a research and development organism are also considered to result in low-medium exposure.

Should the notified strain be proposed for any other uses, such as the ones indicated above, medium-high potential for exposure to humans may result. Given the medium hazard potential for immuno-compromised individuals, the elevated exposure could increase potential human health risks, particularly in that subpopulation. On this basis, the application of SNAc provisions was recommended, as mentioned above. However, the SNAc provisions will allow its use in bioremediation, for production of enzymes and biochemicals and as a research and development organism without any further re-notification since these activities are not likely to impact immune-compromised individuals.

References

Environment Canada and Health Canada (2011), “Framework for Science-Based Risk Assessment of Micro-Organisms Regulated under the Canadian Environmental Protection Act, 1999”.

All other references used in preparation of this report contained proprietary information and were therefore excluded at the request of the notifier.