In anaerobic “butyric–isopropyl” fermentation of carbohydrates by certain bacteria (e.g., Clostridium), which products are typically formed?

Introduction / Context:
Clostridial fermentations encompass several product patterns: ABE (acetone–butanol–ethanol), IBE (isopropanol–butanol–ethanol), and acidogenic routes yielding volatile fatty acids (VFAs) like acetate and butyrate. The term “butyric–isopropyl fermentation” refers to pathways where isopropanol is produced (via reduction of acetone) alongside typical acidogenic products.

Given Data / Assumptions:

• Substrate: carbohydrates under anaerobic conditions.
• Microorganisms: Clostridium species capable of shifting between acidogenesis and solventogenesis.
• Products may include acids (butyric, acetic) and reduced solvents (isopropanol), with minor polyols possible under certain conditions.

Concept / Approach:
During acidogenesis, Clostridia produce acetic acid and butyric acid from sugars, reducing pH. Under solventogenesis, acids are reassimilated to solvents; acetone can be reduced to isopropanol in IBE strains. Some conditions can lead to small amounts of diols (glycols), though yields vary. Thus, a mixture containing butyric acid and acetic acid is typical, and isopropanol production characterizes the “isopropyl” variant, with glycols possible depending on strain and redox balance.

Step-by-Step Solution:
Recognize acidogenesis products: acetate and butyrate.Note solventogenic shift: acetone reduced to isopropanol in IBE pathways.Account for potential minor glycol formation under certain metabolic fluxes.Therefore, all listed products can appear in “butyric–isopropyl” fermentations.

Verification / Alternative check:
Process data from IBE strains documents co-production of isopropanol with residual acids; metabolic engineering papers also note diol by-products under specific conditions.

Why Other Options Are Wrong:
Choosing only one product ignores the mixed-acid/solvent nature of these fermentations.

Common Pitfalls:
Confusing ABE (acetone dominant) with IBE (isopropanol dominant) and overlooking acidogenesis stages that precede solvent production.

Final Answer:
All of these