SYNOPSISBiodegradation 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 uitro aerobic culture system that was designed to capture 14C02 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 14C02 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 14C02.The amount of biodegradation that was observed with cellulose [l-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 [l-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 14C02 in 29 days. The high level of microbial utilization of carbon from both cellulose esters and its conversion to C02 confirms the biodegradability of these polymers and the potential they have for total mineralization in natural microbiologically active environments.

Cellulose is one of nature's most abundant structural materials, providing the primary framework of most plants. For industrial purposes cellulose is derived from two primary sources, cotton linters and wood pulp. Cellulose esters are commonly derived from natural cellulose by reaction with organic acids, anhydrides, or acid chlorides. Cellulose esters of almost any organic acid can be prepared, but because of practical limitations esters of acids containing more than four carbon atoms have not achieved commercial significance. Cellulose acetate is the most important organic ester because of its broad application in fibers and plastics; it is prepared in multi‐ton quantities with degrees of substitution (DS) ranging from that of hydrolyzed, water‐soluble monoacetates to those of fully substituted triacetate. Although cellulose acetate remains the most widely used organic ester of cellulose, its usefulness is restricted by its moisture sensitivity, limited compatibility with other synthetic resins, and relatively higher processing temperature. Cellulose esters of higher aliphatic acids, C 3 and C 4 , circumvent these shortcomings with varying degrees of success. Mixed cellulose esters containing acetate and either the propionate or butyrate moieties are produced commercially in large quantities by Eastman Chemical Co. in the United States. The properties, manufacturing methods, uses, economics, and safety of organic esters of cellulose are discussed.