(556c) Biodegradability Study of Native Corn Thermoplastic Starch In Laboratory Scale: Influence of Plasticizer Concentration, Ageing, Sample Superficial Area and Soil Source

Authors: 
Ballesteros, D. E., Universidad de Los Andes
Merchan, J. P., Universidad de Los Andes
Jimenez, I. C., Universidad de Los Andes
Medina, J. A., Universidad de Los Andes
Salcedo, F., Universidad de los Andes
Alvarez, O., Universidad de Los Andes


Aerobic biodegradation of different samples of native corn thermoplastic starch (TPS) were accordingly evaluated with standard test method ASTM D 5988 ? 03 in order to establish the effect of plasticizer concentration, ageing, sample superficial area and soil source in TPS biodegradation.

Samples were prepared using glycerin as plasticizer, varying its concentration at 30%, 35% and 40%. Dry native corn starch and glycerin were premixed in a blending machine and then extruded in a single screw extruder; pellets and TPS film were obtained after double-step extrusion. Pellet samples were aged during 70 and 90 days in polyethylene bags at room temperature.

Two different soils from a local landfill (Doña Juana, Bogotá/Colombia) and germination peat were used as degradation matrix. Soils were characterized for amylolytic microorganisms, mesophilic aerobic bacteria and fungi, as well as for physical-chemical properties as pH, carbon and moisture content.

Biodegradation rate was assessed by exposing the TPS samples to the soil and measuring the carbon dioxide evolved by microorganisms as a function of time. Carbon dioxide production was measured for TPS samples and was expressed as a percentage of the calculated initial carbon content of samples.

We found that for non-aged samples the increasing plasticizer concentration lead to a higher biodegradation rate. On the other hand, for aged samples, plasticizer concentration negatively affects degradation rate. It was also seen that samples superficial plays a big role in biodegradation rate while no significant difference was observed for different soils.