Physical properties of microbial suspensions

Abstract

Physical properties of suspensions ofSaccharomyces cerevisiae, Candida utilis andEscherichia coli (density, viscosity and surface tension) were measured in synthetic suspensions formed of oentrifuged biomass and supernatants from various stages of batch cultivation in the range from 0 to 10% w/v for yeasts and from 0 to 0.25% w/v for bacteria. Surface tension was also measured in native suspensions in the range of 0 ≦C _m ≦ 2.0% w/v. All single cell suspensions were found to be Newtonian in behaviour. Densities strictly obey the mixing law, viscosities ofSaccharomyces cerevisiae suspensions were correlated by an empirical relation in dependence of C_m andt, surface tensions were correlated graphically for suspensions ofSaccharomyces cerevisiae andEscherichia coli, sinoe experiments with both microorganisms have shown that the previously published approximate correlation can safely be used.