THERMAL AND STORAGE STABILITY OF SACCHAROMYCES-CEREVISIAE (BAKERS-YEAST) ALLERGENS

The effect of storage and high temperatures on the stability of Saccharomyces cerevisiae allergens was studied by immunoblotting. Saccharomyces cerevisiae allergic serum pool and I-125- and galactosidase-labelled anti-IgE were used in the assays. Freeze-dried extracts were reconstituted with saline and with 50% glycerol and then stored at room (+20-degrees-C) and refrigerator temperature (+6-degrees-C) for different time periods. The stability was better in 50% glycerol at +6-degrees-C than at room temperature without glycerol. However, after 1 month, two of the most important allergens of S. cerevisiae, the 48 and 32 kDa protein allergens, lost their IgE-binding capacity even in the extracts stored with 50% glycerol at +6-degrees-C. The 45 kDa allergen was, on the other hand, quite stable after storage for 9 months at +6-degrees-C. Although the beneficial effect of 50% glycerol was clear, storage at +6-degrees-C, even with 50% glycerol should not exceed 1 month for S. cerevisiae extracts. Two commercially available S. cerevisiae extracts in solution with valid expiry dates were also analysed. They had only little allergenic potency, while a freeze-dried extract stored for 8 years showed good allergenic potency. Heating S. cerevisiae extracts resulted in precipitation, the precipitated fraction contained almost all the specific proteins as judged by electrophoresis and IgE detection. The supernatant fraction contained only a few allergens.