N. Pereira et Jd. Bulock, THE IONIC CHARACTER OF THE ENVIRONMENT IN THE FLOCCULATION OF PICHIA-STIPITIS, Revista de Microbiologia, 25(1), 1994, pp. 51-56
Although cells of a flocculation strains of Pichia stipitis became com
pletely dispersed by washes in distilled water, they reflocculated whe
n suspended in solutions of individual medium components. Ionic streng
th was suspected to be the primary cause behind flocculation. The meas
urement of the electrical conductivity showed to be a practical way of
evaluating the ionic strength of the environment. Accordingly, floccu
lation was more intense as the electrical conductivity of the aforemen
tioned solutions increased. At higher values of electrical conductivit
y (> 1000 muS) the degree of flocculation was nearly constant, suggest
ing that charge reduction associated with conformational changes in ce
ll wall proteins may be responsible for cell aggregation. Additionally
, a decrease in electrical conductivity of the medium, through dialysi
s, reduced the ability of the cells to flocculate. The ionic character
of the medium showed to be an important influencing factor in floccul
ation.