ARS | Publication request: Effects of biodegradable plastics on the predominant culturable bacteria associated with soil aggregate formation and stability after 9 months of incubation in natural soil

Submitted to: American Society of Microbiologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 4, 2012
Publication Date: N/A

Technical Abstract: An in vitro study of the effects of biodegradable plastics on the predominant soil aggregating bacteria associated to soil aggregate formation and stability after 9 months of incubation in soil. Caesar-TonThat TC, Fukui R*, Caesar AJ., Lartey, RT, and Gaskin, JF. USDA-Agricultural Research Service, Sidney, MT, USA and *University of Utsunomiya, Japan. Among the greatest advantages of using biodegradable plastics are lower accumulation of bulky plastic materials in the environment and reduction in the cost of waste management. Biodegradable plastics can be recycled by microorganisms, but little is known about the composition of the predominant culturable bacterial communities associated with the biodegradable materials that might function as efficient soil aggregators, and therefore influence aggregate stability. In this study, treatments consisting of soil amended with five biodegradable plastics (poly-starch (EcoplagreenTM), poly-lactic acid (TerramacTM), poly-butylene succinate/carbonate (IUPECTM), poly-starch (Mater-BiTM), and cellulose-acetic acid (CELGREENTM) and a control sample without plastic added were used. After 9 months of incubation of the biodegradable plastic pellets in soil under controlled environment, results indicated aggregate formation in all the treatments. Soil dry-sieving technique showed no difference in the different fractions of soil aggregates (4.75-2.00; 2.00-1.00; 1.00-0.25; 0.25-0.00 mm diameter) between the treatments. However, the soil wet-sieving technique showed that large macroaggregates (>4.75-2.00 mm) from soil amended with poly-butylene succinate/carbonate (IUPECTM) had significant lower water aggregate stability compared to all the other treatments. The predominant bacterial communities from plastic amended and unamended soils were isolated using spiral plating and the bacterial isolates were subjected to a soil sedimentation assay to assess their ability to aggregate soil particles in solution. Results indicated that the proportion of soil aggregating bacteria was lower in soil amended with poly-butylene-succinate/carbonate (IUPECTM) compared to the other treatments suggesting that poly-butylene succinate/carbonate might influence the growth and survival of these populations. This study demonstrates that cultural methods of isolating the predominant bacterial populations combined with a soil sedimentation assay can be useful to identify specific soil-aggregating bacterial populations associated with the biodegradable materials.