The "Family Members" of Bio-Based Films — Where Do They Come From?

1. Direct Natural Polymer Films

• Starch-based films:
  Derived from widely available, low-cost sources like corn, potatoes, and cassava. However, pure starch films are brittle and prone to moisture absorption, often requiring chemical modification.

• Cellulose-based films:
  Sourced from wood, cotton, or agricultural residues. These films offer high transparency and excellent oxygen barrier properties but have poor water resistance. Cellophane (regenerated cellulose film) is a well-known example.

• Protein-based films:
  Made from soy protein, corn zein, or whey protein. They exhibit superior oxygen barrier and freshness-preserving properties but are fragile and costly.

• Chitosan-based films:
  Derived from shrimp and crab shells. Naturally antibacterial, these films hold great potential in food preservation applications.

2. Microbially Synthesized Polymer Films

• Polyhydroxyalkanoates (PHA) films:
  Produced via microbial fermentation. These materials closely resemble conventional plastics in performance, with excellent biocompatibility and biodegradability, though production costs remain high.

3. Monomer-Synthesized Bio-Based Polymer Films

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