Cell lysis assay. A) α-glucosidase detection assay. A sample from the bioreactor was centrifuged and the supernatant was separated from the cells that were lysed. Lysed cells and supernatant were incubated at 37°C with pNPG. The appearance of color (measured as absorbance at 405 nm) is due to the presence of α-glucosidase in the reaction. B) SDS-PAGE and Western Blot of culture samples using antiNoV serum. The first four lanes correspond to lysed cells at the end of the fermentation and last lane to a control spiked with NoV VLPs.