Priming effect of glucose polymers in soil-based biodegradation tests

Plastics formulated for biodegradability often contain glucose polymers as modified starch or cellulose. When measured by the net CO2 evolution method, the mineralization of glucose in soil is overestimated due to its priming effect on soil organic matter mineralization. Measuring both net CO2 evolution and 14CO2 evolution from soil spiked with 14C-labeled starch and cellulose, we found their priming indexes similar to that of glucose. Priming by glucose monomers formed during depolymerization of starch or cellulose-based plastics may lead to an overestimation of their biodegradability in the net CO2 evolution test. Though structurally-close to glucose, fructose and inositol failed to elicit any priming.