New substances: risk assessment summary 22152

Overview

Notified organism: Saccharomyces cerevisiae strain containing a carboxy-lyase gene from a foreign organism, overexpressing a native transporter protein gene

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

Organism type: Yeast

Use: Manufacture of the notified S. cerevisiae strain for export for use in bioethanol production outside Canada

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: Not eligible for addition to the Domestic Substances List

Recommended action: None

Waiver: None

Synopsis

The notified strain was notified for manufacture in a single facility for export for use in bioethanol production outside Canada.

There is no evidence to suggest a potential risk of adverse environmental effects at the exposure levels predicted to the environment from the intended manufacture for export. Owing to the low potential for hazard and the low potential for exposure, the notified strain is not suspected to meet criteria in paragraphs 64(a) or (b) of CEPA.

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 manufacture of the organism for export only. Owing to the low potential for hazard and low potential for exposure, the notified strain is not suspected to meet criteria in paragraph 64(c) of CEPA. No further action is recommended.

Background information

The notified strain is a genetically modified derivative of the unmodified parental strain S. cerevisiae, with the insertion of a carboxy-lyase gene from a foreign organism and a native transporter protein gene from S. cerevisiae. The genetic modifications are intended to increase ethanol yield during fermentation and reduce glycerol production.

Hazard

The environmental hazard potential of the notified strain is determined to be low because:

• the notified strain was genetically modified from its parental strain by stable integration of synthetized and characterized genes from well-known donors with no history of environmental adverse effects
  • it can be distinguished from other S. cerevisiae strains and closely related species by its unique genetic modifications
  • there are no environmental hazards associated with those modifications
• the parental strain has been commercially available for fuel ethanol production outside of Canada for almost a decade with a history of safe use
  • although the notified strain has no history of use in Canada, like its parental strain, it is not expected to exhibit adverse environmental effects
• the potential for transfer of integrated genetic material from the notified strain to other S. cerevisiae is very low given that horizontal gene transfer has rarely been reported in yeast
• the organism was notified under confinement procedures, so pathogenicity and toxicity testing were not required under the NSNR(Organisms)
  • however, literature suggests that S. cerevisiae can rarely cause adverse effects in some aquatic and terrestrial compartments

The human hazard potential of the notified strain is determined to be low because:

• the notified strain is a genetically modified derivative of another S. cerevisiae strain
  • the notified strain is classified as a Risk Group 1 human pathogen by the Public Health Agency of Canada, meaning it presents a low community and individual risk
• the genetic modifications that have been made in the notified strain involve the insertion of codon optimised gene for a carboxy-lyase isolated from a foreign organism and over-expression of a native transporter protein gene
  • these genes are all well characterised and not associated with any pathogenic, toxic or antibiotic resistance effects
• the notified strain is well-characterized and distinguishable from its parental strain and other S. cerevisiae strains
• the genetic modifications are stably integrated into the genome and the probability of any mobilization of the notified strain is unlikely
• although several putative virulence traits have been attributed to certain probiotic and clinical strains of S. cerevisiae such as growth at high temperatures, pseudohyphal growth and high protease and phospholipase activity, in vitro data provided by the notifier indicates that no virulence traits were observed for the notified strain
• there are no reports of allergenicity due to the carboxy-lyase protein
  • expression of the codon optimized carboxy-lyase and native transporter protein genes is not going to enhance the allergenicity potential of the notified strain
• S. cerevisiae has a wide distribution in nature and a long history of use especially in baking and alcohol production
• reports of infections from wild-type S. cerevisiae strains in healthy individuals are rare, but there are documented cases of S. cerevisiae infections predominantly in immunocompromised individuals or those with pre-existing medical conditions
  • these infections are treated using antifungal therapy
• the New Substances (NS) program’s literature searches did not identify any documented cases of infection specifically associated with the parental or notified strains
• the NS program’s modelling predicted values close to zero for disability-adjusted life years (DALYs) indicating no loss of healthy life years due to either premature death or disability, resulting from the exposure of the notified strain to the general population and those with underlying medical conditions
• in the event of infection, clinically relevant antifungal drugs such as fluconazole and Amphotericin B are available for treatment of infections with the notified strain

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

Exposure

The environmental exposure potential of the notified strain is determined to be low because:

• the notified strain will be manufactured for export only in a production facility with confinement procedures
• the notified strain will be manufactured in accordance with the current good manufacturing practices for food (cGMP) and a Hazard Analysis Critical Control Points (HACCP)
  • a layout of the manufacturing facility has been provided along with the description of standard operational procedures to illustrate the effectiveness of restricting the exit or dispersal of the notified strain in environment
• the production facility is designed to control air emissions and the levels of organism predicted to be deposited on soil from air emissions does not represent high levels of exposure
  • occasional accidental releases are possible but given that production occurs in a facility with measures in place to control spills, little to no environmental exposure is anticipated from such an event
  • in the manufacturing process, most live organisms will be harvested, and the live organisms released from air emissions and liquid wastes will not lead to high levels of exposure
• once the notified strain reaches the environment, it is likely to survive and persist for some time
  • its potential for air/liquid waste dispersal in the urban environment is low, and therefore it is not expected to be dispersed a great distance from its point of release
• inactivation data for surrogate strains were provided and indicate that the large amount of yeast waste biomass produced in each fermentation cycle would be thermally or chemically inactivated before disposal in environment
• there are no significant anticipated releases of biomass of notified strain from production as it is the desired product that will be exported
  • the remaining waste liquid will be treated prior to disposal in the municipal wastewater system and remaining organisms will be effectively treated in a wastewater treatment plant
• this strain was notified under Schedule 1 with confinement procedures for export only
  • any other potential use(s) of the strain without confinement in Canada will require a new notification under the NSNR(Organisms)

The indirect human exposure potential of the notified strain is determined to be low because:

• the notified strain is a proprietary strain and will be manufactured in a single facility Canada
  • it is intended for export to customers outside of Canada
• a layout of the manufacturing facility has been provided along with the description of operational and confinement procedures to restrict the exit or dispersal of the notified strain
• the notifier states that all manufacturing plant personnel have adequate training, and standard operating procedures are in place to deal with any accidental spills or loss of culture
• measures are in place to inactivate all gaseous, liquid and solid wastes from the manufacturing facility
• using the NS program’s modelling, worst case scenario estimates calculated for accidental releases to air, soil and water from the manufacturing facility indicated potential releases into the environment
• there are reports in the literature indicating potential for survival and establishment for up to 12 months in soil
  • conditions such as temperature, water saturation, soil type, as well as lack of availability of sugar or organic matter are expected to reduce the survival and persistence of the notified strain in the environment leading to minimal exposure to humans in case of accidental releases
  • S. cerevisiae is generally not known to persist in receiving environments for a long time or outcompete native strains
• although no other potential uses were identified for the notified strain, the exposure to humans is expected to be similar to the accidental release scenarios predicted by the NS program’s modelling considered in this assessment
  • in all scenarios, the concentration at which humans would be exposed to the notified strain from environmental media is lower than the concentration at the point of introduction from the manufacturing facility in case of accidental release

Risk characterization

Owing to the low potential hazard and the low potential exposure, the environmental risk associated with the manufacture of the notified S. cerevisiae strain for export and potential uses such as its use in bioethanol production in Canada is determined to be low.

Owing to the low potential hazard and the low potential exposure, the human health risk associated with the manufacture of the notified S. cerevisiae strain in Canada for export is assessed to be low.

Risk assessment conclusion

There is no evidence to suggest a potential risk of adverse environmental effects at the exposure levels predicted to the environment from manufacture of the notified S. cerevisiae strain for export as well as other foreseeable potential uses that may result in introduction of the notified S. cerevisiae strain into the environment. The risk to the environment associated with the notified S. cerevisiae strain is not suspected to meet criteria in paragraphs 64(a) or (b) of CEPA. No further action is recommended.

There is no evidence to suggest a risk of adverse human health effects at the exposure levels predicted for the general population of Canada from the manufacture of the notified S. cerevisiae strain for export. The risk to human health associated with the notified S. cerevisiae strain is not suspected to meet the criteria in paragraph 64(c) of CEPA, for these activities in Canada. No further action is recommended.