For Eremothecium ashbyii and Ashbya gossypii (riboflavin-producing fungi), why must cultures and fermentation residues be sterilized before disposal?

Introduction / Context:
Eremothecium ashbyii and Ashbya gossypii are classic industrial riboflavin (vitamin B2) producers. Beyond their biotechnological value, they have ecological and plant-health implications. Proper waste treatment is a key biosafety consideration in fermentation facilities.

Given Data / Assumptions:

• The organisms listed are filamentous ascomycetes associated with plants.
• Industrial processes may generate biomass and spent broth requiring safe disposal.
• The question asks the reason for mandatory sterilization before discard.

Concept / Approach:
Ashbya gossypii (syn. Eremothecium gossypii) and Eremothecium ashbyii have been described as plant-pathogenic or plant-associated fungi (e.g., affecting cotton and related hosts). Accidental release could pose phytopathological risks. Therefore, deactivation of biomass by sterilization mitigates environmental dissemination.

Step-by-Step Solution:
Identify the organisms’ ecological role → plant-associated with pathogenic potential. Industrial biosafety best practice → sterilize cultures/residues prior to disposal. Select the reasoning that they are plant pathogens → correct safety rationale.

Verification / Alternative check:
Industrial microbiology guidelines emphasize sterilization of wastes when production strains may be plant pathogens or could persist in the environment.

Why Other Options Are Wrong:
Human pathogens: not the primary classification for these species. Plant mutants: imprecise and irrelevant to biosafety. Bacteriophages: viruses of bacteria, unrelated here.

Common Pitfalls:
Assuming any production organism is harmless; pathogenicity to plants can still necessitate strict waste treatment.

Final Answer:
They are plant pathogens.