Optically monitoring Baker's yeast (Saccharomyces cerevisiae) growing in an air-fluidized/expanded potato starch matrix

Summary

In order to study cell behavior in solid fermentation processes, model systems using gelatin and starch have been developed to track Baker's yeast growth. The difficulty in estimating the cell concentration within solid materials arises because both the solid material and the cellular material contribute to the measurement (such as optical resistance). In general, however, the two materials cannot be easily separated, hence the need to measure the cells along with the solid supporting material. A simple spectrophotometric method has previously been shown to work well in both aerated submerged batch cultures and aerated static solid cultures. The optical approach is applied here to monitor a more complex solidified system: cell growth in a novel air-fluidized/expanded bed of yeast growing on a starch matrix. Conventional assays for reducing sugar, total extracellular protein, and extracellular lysine were also applied to monitor yeast behavior in this new system.