The disruption of Alcaligenes eutrophus by high pressure homogenisation: key factors involved in the process.

The disruption of the Gram-negative bacterium Alcaligenes eutrophus by high pressure homogenisation, using the APV Gaulin 15M 8BA and 30CD homogenisers is reported. The operating parameters such as operating pressure, number of passes, temperature and biomass concentration, mimicked trends previously reported for yeasts. Extension of the study to consider the effect of cell characteristics, including the growth rate, size and shape, illustrated the dominant effect of the growth phase. The improved disruption of bacterial cultures in the logarithmic phase with respect to stationary phase cultures was confirmed by an increased dependence of actively growing cultures on the operating pressure. An increase in size in excess of 30% on the accumulation of the storage product, PHB in the stationary phase caused little change in the ease of disruption. The use of transmission electron microscopy to directly monitor the disruption on multiple passes shed light on the two-stage nature of this disruption process.