The recovery of plasmid DNA from cells is achieved by a two-step chemical r
eaction which usually employs sodium hydroxide and sodium dodecyl sulphate
followed by neutralisation with a chilled solution of potassium acetate. It
is important that the gelatinous flee of chromosomal DNA with proteins deb
ris is not broken down since fragments of chromosomal DNA are difficult to
separate from plasmid DNA. To accomplish the operation at scale demands kno
wledge of the rheology as the reactions proceed. In this paper a co-axial c
ylinder rheometer is used to record the changes for two strains of Escheric
hia coli cells. Analysis of the liquor, prior to neutralisation indicates t
hat at shear rates below 367 s(-1) the flow properties during lysis are non
-Newtonian, but above 367 s(-1) flow behaviour becomes Newtonian. Additiona
lly, following neutralisation, the rheological data show that the clear liq
uor obtained at low shear levels is Newtonian, but the gelatinous floc has
strong viscoelasticity. These properties strongly influence subsequent stag
es for the removal of solids.