Cell Immobilization Supports — For Bacillus subtilis, which of the following materials has been employed as a support matrix for immobilizing whole cells?

Introduction:
Whole-cell immobilization uses solid supports to retain active biomass while allowing substrates and products to flow. Bacillus subtilis, a robust Gram-positive bacterium, has been immobilized on various carriers in reactors for biotransformations and wastewater applications. This question asks you to identify a support material that has been used for immobilizing such cells.

Given Data / Assumptions:

• Focus is on practical, mechanically stable supports for biofilm or attached growth.
• Bacillus species adhere well to rough, porous, carbonaceous media.
• Operating environments may include packed beds or trickle filters.

Concept / Approach:

Anthracite has long served as a granular support/pacing medium owing to its rigidity, porosity, and large surface area that fosters microbial attachment. Its hydrophobic character and durability make it suitable for repeated operation, backwashing, and sustained biofilm formation without significant attrition, making it a recognized option for immobilizing Bacillus cells.

Step-by-Step Solution:

Verification / Alternative check:

Reports of attached-growth reactors and trickling filters document anthracite as an effective carrier for Bacillus biofilms, supporting high cell densities and stable operation.

Why Other Options Are Wrong:

A and D can be used in specialized chemistries but are not the canonical granular medium for this context; B (gelatin) lacks mechanical robustness in continuous reactors; E is overly restrictive.

Common Pitfalls:

Confusing enzyme immobilization on chemically activated gels with whole-cell immobilization for reactor packing; the design criteria differ.

Final Answer:

Anthracite (granular carbonaceous support)