2001-09-27-世界卫生组织-Safety_assessment_of_foods_derived_from_genetically_modified_microorganisms_29页_95kb

Summary of the Joint FAO/WHO Expert Consultation on Foods Derived from Genetically Modified Microorganisms

1. Introduction

A Joint FAO/WHO Expert Consultation on Foods Derived from Biotechnology was held in Geneva from 24–28 September 2001, focusing on the safety assessment of foods derived from genetically modified microorganisms (GMMs). The Consultation involved 27 experts, including authors of discussion papers, and was supported by teleconference participation from international scientists. The goal was to evaluate existing safety assessment methods for genetically modified plants and apply them to GMMs, while also considering unique aspects related to microbial use in food.

2. Background

The Consultation was part of an ongoing initiative by FAO and WHO to provide scientific and technical guidance to Member States on biotechnology-derived foods. The previous consultations had addressed safety assessments for genetically modified plants and allergenicity of biotechnology-derived foods. The Codex Alimentarius Commission, in its 24th Session, requested the development of guidelines for food safety assessment of modified microorganisms, prompting this Consultation. The Consultation aimed to build on previous findings and assess whether current approaches for evaluating genetically modified plant-derived foods could be extended to GMMs.

3. Scope

The Consultation focused on the safety assessment of foods derived from genetically modified microorganisms using recombinant DNA techniques. It considered three types of foods:

• Foods and ingredients containing viable GMMs
• Foods and ingredients containing non-viable GMMs
• Foods and ingredients produced by fermentation using GMMs, with the GMM removed

It excluded highly purified products such as food additives, enzymes, and flavors derived from GMMs, as these are already covered by existing safety evaluations. The Consultation also acknowledged that while it did not address environmental or socio-economic issues, the principles outlined are applicable to all foods produced using microorganisms.

4. Safety Assessment

4.1 General Approach to Safety Evaluation

The Consultation emphasized the importance of a case-by-case, stepwise, and integrated approach for assessing the safety of GMM-derived foods. This approach is based on the concept of substantial equivalence, comparing the modified organism to its conventional counterpart. Key principles include:

• Assessing safety for all population groups, including immuno-compromised individuals
• Using sound scientific data and appropriate safety assessment methods
• Characterizing the genetic modification, recipient microorganism, vector, and the GMM itself

Additional considerations include:

• Exposure to GMMs and their potential dietary impact
• Secondary effects from gene expression or DNA disruption
• Differences between microbes and plants, and the influence of the food matrix
• Techniques used for genetic modification
• Genetic stability and pathogenic potential
• Safety and nutritional assessment of the food
• Interactions with intestinal flora and immune system
• Effects of processing, cooking, and storage

4.2 Aspects Specific to Microorganisms

Microorganisms used in food production, such as bacteria, yeasts, and filamentous fungi, have distinct genetic characteristics that require specific safety considerations. Bacteria, in particular, benefit from homologous recombination, allowing precise integration and removal of DNA sequences. The Consultation highlighted the importance of using safe and well-characterized microbial strains, ensuring that genetic modifications do not compromise their safety status.

4.3 Application of Substantial Equivalence to GMMs

The concept of substantial equivalence was introduced as a framework for comparing modified organisms with their conventional counterparts. It is particularly useful for GMMs due to their genetic plasticity and variable gene expression based on environment. The Consultation recommended using molecular profiling techniques, such as DNA microarrays and proteomics, for a more comprehensive assessment. However, it also stressed the need to distinguish normal variation from potential safety concerns and to validate these techniques for routine use.

5. Specific Food Safety Issues

5.1 Introduction

This section outlines specific food safety issues related to GMMs, including:

• Gene transfer between GMMs and other organisms in the food and GI tract
• Safety of genetic markers used in selection (e.g., antimicrobial resistance genes)
• Interaction of GMMs with intestinal microflora and the immune system
• The importance of understanding these interactions to assess potential health risks

5.2 Techniques for Genetic Modification

Genetic modification techniques for microorganisms are better understood than for plants. In bacteria, genes can be inserted into specific sites on the chromosome or plasmids. For yeast and filamentous fungi, similar techniques are used, though integration and stability may vary.

Key considerations include:

• Host microorganism safety and characterization
• Safety of inserted genes and their products
• Use of safe vectors and constructs
• Selection of markers that do not pose a risk
• Methods of DNA transfer to the host, such as conjugation, transformation, and transduction

5.3 Strain Identification and Characterization

Strain identification and characterization are critical for safety assessment. The host microorganism must be well-characterized, safe, and stable. Techniques such as DNA/DNA hybridization and 16S rRNA sequencing are used for taxonomic classification. Phenotypic characterization involves standard physiological and biochemical methods. The Consultation emphasized the need for thorough characterization of both the host and the GMM to ensure safety.

5.4 Gene Transfer

Gene transfer mechanisms in bacteria include conjugation, transformation, and transduction. These processes can lead to the spread of genetic traits, including antimicrobial resistance. The Consultation noted that gene transfer can occur within and between species, and that it is a natural phenomenon contributing to bacterial genomic diversity. The establishment of transferred DNA can occur through genomic integration or plasmid formation, and may be influenced by factors such as sequence homology and restriction enzymes.

6. Conclusions

The Consultation concluded that the safety assessment of foods derived from GMMs should follow a general framework similar to that used for genetically modified plants, but with specific considerations for microorganisms. The concept of substantial equivalence remains central, though its application must account for the unique properties of microbial genomes and their interactions with the human body.

7. Recommendations

• Apply the concept of substantial equivalence to GMMs, considering their genetic plasticity and environmental interactions
• Use molecular profiling techniques for comprehensive safety assessment
• Ensure the safety of the host microorganism, inserted genes, and genetic markers
• Characterize GMMs thoroughly at the genetic and phenotypic levels
• Consider the potential for gene transfer and its implications for public health
• Develop standardized methods for safety evaluation and risk management

8. References

The report references various international organizations and publications, including OECD, WHO, FAO, and ILSI, as well as specific studies on gene transfer mechanisms and safety assessment methodologies.