Growth and lactic acid production in batch culture of Lactobacillus rhamnosus in a defined medium

To facilitate metabolic analysis, batch fermentations of Lactobacillus rham nosus were carried out in a new defined medium. Biomass at 10.5 g/l and lac tic acid at 67 g/l with a Y-P/S of 0.84 were achieved. The maximum specific growth rate and the average productivity were 0.49/h and 2.48 g/l.h, respe ctively. These are comparable to those of this organism and related organis ms in complex media. Preliminary amino acid studies were also conducted, hi ghlighting the importance of serine, asparagine, glutamine and cysteine. Ki netic analysis revealed that lactic acid production was predominantly growt h-associated with growth associated and non-growth associated lactic acid c onstants of 0.389 mol/g-cell and 0.0025 mol/g-cell.h, respectively. Finally a kinetic model has been included to describe the fermentation of L. rhamn osus.