SYNOPSISTwo separate assay systems were used to evaluate the biodegradation potential of cellulose acetate: an in uitro enrichment cultivation technique (closed batch system), and a system in which cellulose diacetate (CDA) films were suspended in a wastewater treatment system (open continuous feed system). The in uitro assay employed a stable enrichment culture, which was initiated by inoculating a basal salts medium containing cellulose acetate with 5% ( v/v ) activated sludge. Microscopic examination revealed extensive degradation of CDA (DS = 2.5) fibers after 2-3 weeks of incubation. Characterization of the CA fibers recovered from inoculated flasks demonstrated a lower average degree of substitution and a change in the mol wt profiles. I n uitro enrichments with CDA (DS = 1.7) films were able to degrade > 80% of the films in 4-5 days. Cellulose acetate (DS = 2.5) films required 10-12 days for extensive degradation. Films prepared from cellulose triacetate remained essentially unchanged after 28 days in the in uitro assay. The wastewater treatment assay was less active than the in uitro enrichment system. For example, approximately 27 days were required for 70% degradation of CDA (DS = 1.7) films to occur while CDA (DS = 2.5) films required approximately 10 weeks before significant degradation was obtained. Supporting evidence for the biodegradation potential of cellulose acetate was obtained through the conversion of cellulose [l-14C]-acetate to 14C02 in the in uitro assay. The results of this work demonstrate that cellulose acetate fibers and films are potentially biodegradable and that the rate of biodegradation is highly dependent on the degree of substitution.

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.

Rumen and abomasal cannulas for sheep and an instrument that facilitates rapid insertion of the cannulas were developed. The cannulas were made from epoxy-filled polyurethane and were supported by outer support rings held in place by nuts screwed onto the threaded tops of the cannula barrels. The insertion device was used to pull the cannula through a separately made incision in the abdominal wall and to stretch the skin and other tissues over a cone and onto the barrel of the cannula, thus ensuring a tight fit and the formation of a ring of scar tissue that virtually eliminated digesta leakage. Expansion plugs, used to seal the cannulas, were designed to eliminate a twisting force that could be transferred to the cannula when the plugs were secured or released. The plugs were also designed to protrude minimally from the side of the animal. More than 75 sheep were cannulated, and the preparations proved to be relatively maintenance free and resistant to mechanical disturbance by the animal. The cannulas had a long functional life and permitted convenient sampling of digesta and introduction of liquid and solid materials, including digestion bags.