A closely related study used 500 ml batch cultures controlled at
pH between 4.5 and 7.5 using 50 g/L pure glycerol as substrate and
a similar media formulation otherwise as the current study
(6.54 mM phosphate) (Biebl, 2001). The study reported finding
great variation in product formation, however no correlation to
pH was found accept for ethanol. Cell growth was found to be more
or less equal over the pH range applied, in contrast to the data
reported in this study. In general there was great variability in product
formation under equal or slightly different conditions, a cause
that was hypothesized to be due to weak pathway regulation and/
or multiplicity effects.