Biodegradability of Packaging Materials: Quantitative Evaluation by an Automated Respirometric Method Applied to their Insoluble Constituents as Starch

An automated headspace method to measure the CO 2 evolved is described and developed into a biodegradation test procedure for insoluble substrates. The test system consists of a bioreactor with a working volume of 1.51, fitted with temperature, pH and dissolved oxygen partial pressure control. These parameters enable us to work at the optimal growth conditions for Bacillus amylolicheniformis MIR-41. The study was carried out under continuous aerated conditions at 0.5 and 1.0 v.v.m. Glucose was used as a reference compound because it is completely assimilated by Bacillus amylolicheniformis MIR-41. The percentage of carbon converted into CO 2 was the parameter used to determine the optimal aeration conditions for the biodegradability of wheat starch, a possible packaging material component. The present method was adapted to insoluble substrates at high concentrations for the first time. The reliability of this method was tested by simultaneous measurement of the biomass produced. The carbon content of the biomass is closely correlated with the carbon of the evolved CO 2 . It was also found that production of α-amylase was correlated with CO 2 evolution during exponential growth. Finally, these study validates CO 2 measurement as an assessment of the extent of biodegradation of insoluble substrates, even at high concentrations.