Accelerated Biodegradation of Cellulosic Substrates.

Utilization of appropriate chemical/physical/micro­ biological techniques for pretreatment of cellulosic sub­ strates was shown to significantly accelerate cellulose biodegradation processes under both laboratory and in situ marine conditions. Initially an overlay plating system was developed for the isolation of cellulolytic bacteria. The procedure involved a double-layer agar system, with the basal portion consisting of a mineral salt/yeast extract agar and the upper portion, an alkali-treated cellulose­ agar overlay. The system was shown to have limited appli­ cation in the enumeration of cellulolytic bacterial populations. An in situ rate of 3.8 mg solubilized/24 hr/gram substrate was determined for the decomposition of untreated, purified cellulose. Introduced (purified cellulose) sub­ strate was degraded, in situ, at a rate 2.7 times slower than that for the indigenous substrate, Spartina. This indicates that processed cellulose wastes are even more recalcitrant than are natural cellulosics. A combination of nitrite-photochemical, alkali, and bacteria seeding pre­ treatments was shown to increase the rate of cellulose solubilization by a factor of 6.5. In laboratory studies, pretreated cellulose samples were solubilized in cadoxen and analyzed for determination of their degree of polymerization (DP). Ball-milling or UV-nitrite irradiation lowered the DP to a greater extent than did alkali treatment or UV-no nitrite irradiation. However, bacterial degradation rates for the cellulosics indicated that in effecting an increase in cellulolytic rates, DP is of secondary importance compared to the degree of swelling or bacterial accessibility of the cellulose fiber. Low DP, highly crystalline substrates were shown to have lower digestion rates than did higher DP, less crystalline celluloses. Pretreatments for accelerating cellulose biodegra­ dation were also examined with respect to their action on compounds occurring concomitantly with cellulosics. Electron-capture gas chromatographic studies indicated that a 90+\ reduction of polychlorinated biphenyl (PCB) residues in cellulosics could be achieved by appropriate UV irradia­ tion. PCB\u27s in untreated cellulosic substrates were shown to remain stable throughout conventional cellulose decompo­ sition processes and to be concentrated in the microbial­ cellulose biomass during biodegradation. A proposal was presented which suggested incorporation of UV irradiation treatment into waste cellulose-SCP systems (or any recycling processes) where bioconcentration of PCB re idues may pre­ sent a significant potential danger. The study indicated that environmental considerations of accelerated cellulose biodegradation parallel similar problems in microbial SCP-cellulose processes. Objectives of suc;1 increased cellulose utilization technology include maximizing substrate conversion to desirable compounds con­ currer,t with removal of toxic materials. Substrate pre­ tr atment tP hniques were shown to have potential as solu­ tions in meeting the above objectives