An investigation into the preservation of microbial cell banks for alpha-amylase production during 5 l fed-batch Bacillus licheniformis fermentations

Fluorescent staining techniques were used for a systematic examination of methods used to cryopreserve microbial cell banks. The aim of cryopreservation here is to ensure subsequent reproducible fermentation performance rather than just post thaw viability. Bacillus licheniformis cell physiology post-thaw is dependent on the cryopreservant (either Tween 80, glycerol or dimethyl sulphoxide) and whilst this had a profound effect on the length of the lag phase, during subsequent 5 l fed-batch fermentations, it had little effect on maximum specific growth rate, final biomass concentration or alpha-amylase activity. Tween 80 not only protected the cells during freezing but also helped them recover post-thaw resulting in shorter process times.