I have finished compiling the data on batch culture propagations conducted with five of the Brettanomyces strains. The following two graphs contain data from the standardized propagation method described in the previous post using 12 °Plato (1.048 gravity) wort as the growth medium. Some variation between growth patterns can be seen along with what appears to be step-like growth until the stationary phase is reached after a period of 168 to 192 hours. More information on Propagation and Batch Culture Growth can be found by following the link.
Growth curve for five strains of Brettanomyces during semi-aerobic batch culture.
Cultures were grown in 500 ml of wort substrate over a 288-hour
period at 28°C with 80-rpm agitation. Viability was taken into
account to reflect the actual cell number.
*Methylene Blue staining technique… The use of methylene blue to stain cells in order to determine viability proved difficult with Brettanomyces spp. I found often that cells which were viable would take up the methylene blue into the vacuoles, giving a false positive. Some would take it into the cell cytoplasm but not into the vacuole. The dye would only appear near the tips giving the cells two blue dots at each end. I have spoke with other brewers who have had trouble using methylene blue to yield positive results when doing viability checks on Brettanomyces strains. I would say from the lab experience I had and daily cell counts that an alternative method would be advantageous as I don’t believe methylene blue yields completely accurate results.