Co-encapsulation of amyloglucosidase with starch and Saccharomyces cerevisiae as basis for a long-lasting CO2 release

CO₂ is known as a major attractant for many arthropod pests which can be exploited for pest control within novel attract-and-kill strategies. This study reports on the development of a slow-release system for CO₂ based on calcium alginate beads containing granular corn starch, amyloglucosidase and Saccharomyces cerevisiae. Our aim was to evaluate the conditions which influence the CO₂ release and to clarify the biochemical reactions taking place within the beads. The amyloglucosidase was immobilized with a high encapsulation efficiency of 87% in Ca-alginate beads supplemented with corn starch and S. cerevisiae biomass. The CO₂ release from the beads was shown to be significantly affected by the concentration of amyloglucosidase and corn starch within the beads as well as by the incubation temperature. Beads prepared with 0.1 amyloglucosidase units/g matrix solution led to a long-lasting CO₂ emission at temperatures between 6 and 25?°C. Starch degradation data correlated well with the CO₂ release from beads during incubation and scanning electron microscopy micrographs visualized the degradation of corn starch granules by the co-encapsulated amyloglucosidase. By implementing MALDI-ToF mass spectrometry imaging for the analysis of Ca-alginate beads, we verified that the encapsulated amyloglucosidase converts starch into glucose which is immediately consumed by S. cerevisiae cells. When applied into the soil, the beads increased the CO₂ concentration in soil significantly. Finally, we demonstrated that dried beads showed a CO₂ production in soil comparable to the moist beads. The long-lasting CO₂-releasing beads will pave the way towards novel attract-and-kill strategies in pest control.