Indexed on: 01 Jun '95Published on: 01 Jun '95Published in: Biotechnology Techniques
A method for estimating microbial cell concentration in suspension cultures even under heterogeneous conditions was developed on the basis of changes in osmotic pressure of the medium. During batch cultivation of Saccharomyces cerevisiae and Candida brassicae, there was a linear relationship between increase in cell concentrations (ΔX) and the difference between osmotic pressure change in the broth (ΔPc) and the osmotic pressure increase due to product accumulation (ΔPp) regardless of the product (ethanol) concentration in the broth. A linear relationship between (ΔX) and (ΔPc — ΔPp) was also observed when medium containing solid substrate (wheat germ) was used. An enzymatic method for separating cells from the solids was developed and cell concentrations in broths containing solid substrates could be measured accurately. During the batch production of bialaphos (a herbicide) by Streptomyces hygroscopicus using a medium containing solid substrates, the cell concentration could also be estimated by the developed methods.