Storage behaviour of immobilized dried micro-organisms

Abstract

In two sets of experiments the immobilized cells of the wine yeastSaccharomyces cerevisiaeand the mixed culture ofLactobacillus bulgaricusandStreptococcus thermophiluswere dried and tested for storage ability at 4°C. Both κ-carrageenan and alginate were used as entrapment matrices. The beads with the cells were either dried right after immobilization or activated prior drying. Air flow over a flat bed of beads was employed as the drying method. ForS. cerevisiaethe best results were attained with the primarily activated (activation prior drying) alginate entrapped cells. This corresponds to 69.5% activity retention measured as ethanol productivity at the end of 7 weeks of storage based on the activity of the non-dried beads. For the lactic acid bacteria mixed culture, no activity was detected for the directly dried beads. For the primarily activated (activation prior drying) cells, it was observed that upon drying the activities of κ-carrageenan and alginate entrapped cells decreased to about 77 and 73%, respectively, after 36 days of storage taking non-dried beads as a reference in terms of lactic acid production. For both matrices primarily activated beads required longer period of drying over directly dried ones.