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The plastic pollution crisis: Most synthetic polymers (PE, PP, PVC, PS) are non-biodegradable — they persist for hundreds of years. The C-C backbone is not efficiently broken by any natural enzyme. Solutions include recycling, incineration with energy recovery, and biodegradable alternatives. PHBV (poly-beta-hydroxybutyrate-co-beta-hydroxyvalerate): A copolyester produced by bacteria from organic waste. Fully biodegraded by soil microorganisms. The HB:HV ratio controls properties (more HV → more flexible). Used in packaging, drug delivery, orthopedic implants, surgical sutures. Nylon-2-nylon-6: Copolymer of glycine (2C amino acid) and 6-aminocaproic acid (6C). The polyamide structure resembles natural proteins → proteolytic enzymes can degrade it. Regular nylon-6,6 is NOT biodegradable (too-long hydrocarbon segments between amide groups for enzymes to recognize). PLA (polylactic acid): Made from corn starch (renewable). Biodegradable polyester used in absorbable sutures, food packaging. PGA (polyglycolic acid): Absorbable surgical suture material. JEE specifically tests: PHBV (most commonly asked), why normal plastics are non-biodegradable, and the concept of biodegradability linked to enzyme recognition of polymer structure.