Biodegradation of radiolabeled cellulose acetate and cellulose propionate

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Biodegradation of cellulose acetate and cellulose propionate was conclusively established with a naturally derived mixed microbial culture derived from activated sludge and 14C labeled cellulose esters. Radiolabeled cellulose esters were synthesized with either [1‐14C]‐acetate or [1‐14C]‐propionate and back hydrolyzed to the desired degree of substitution (DS) ranging from 1.77 to 2.64. Biodegradation was measured in an in vitro aerobic culture system that was designed to capture 14CO2 produced by the aerobic microbial metabolism of the cellulose esters. Microorganisms were able to extensively degrade cellulose [1‐14C]‐acetate (CA) with DS ranging from 1.85 to 2.57 over periods of 14–31 days. More than 80% of the original 14C‐polymeric carbon was biodegraded to 14CO2 for CA substrates with a DS of 1.85. CA polymers with a DS of 2.07 and 2.57 yielded over 60% conversion to 14CO2. The amount of biodegradation that was observed with cellulose [1‐14C]‐propionate with DS of 2.11, 2.44, and 2.64 were lower than the corresponding acetyl ester and ranged from 0.09 to 1.1%. However, cellulose [1‐14C]‐propionate with a DS of 1.77 and 1.84 underwent very rapid degradation in the mixed culture system, with 70 to over 80% conversion of labeled polymeric carbon metabolized to 14CO2 in 29 days. The high level of microbial utilization of carbon from both cellulose esters and its conversion to CO2 confirms the biodegradability of these polymers and the potential they have for total mineralization in natural microbiologically active environments.