Vitamin B12 fermentation — Aerated, submerged bacterial processes for cobalamin production most commonly employ which genera as production strains?

Introduction / Context:
Vitamin B12 (cobalamin) is an industrially important cofactor used in foods and pharmaceuticals. Aerated submerged fermentations have historically used specific bacterial producers optimized for cobalamin biosynthesis and corrinoid pathways.

Given Data / Assumptions:

• Propionibacterium spp. (now Cutibacterium for many species) are classic B12 producers under microaerobic/aerobic conditions.
• Some Pseudomonas spp. also produce cobalamin or corrinoids in submerged culture.
• Acetobacter are vinegar bacteria and are not standard B12 workhorses.

Concept / Approach:
Match production organisms to established B12 processes: Propionibacterium and certain Pseudomonas are documented, so the inclusive option is correct.

Step-by-Step Solution:

Verification / Alternative check:
Industrial reviews of cobalamin production consistently highlight propionibacteria and selected pseudomonads.

Why Other Options Are Wrong:

• Only one genus: incomplete relative to known producers.
• Acetobacter: not a conventional B12 platform.

Common Pitfalls:
Assuming a single “best” producer; in practice, multiple genera and engineered strains are used depending on process conditions.

Final Answer:
both (a) and (b)