The presence of a limited nitrogen source did not
restrict the mutant strain from synthesising cellulose,
although to a lesser degree. Because of the composition
of the whey broth, the speci¢c growth rate of the cells is
assumed to be slow and may have resulted in lower total
cell population. This was the case for another A. xylinum
strain [40]. When it was grown in minimal synthetic medium
with 1% glucose as the carbon source, only about
half as much cellulose was synthesised as when it was
grown in the unde¢ned enriched medium. Further to support
this, works on the kinetics of cellulose production
have demonstrated that cellulose production is always associated
with cell growth [41,42]. Rate of cellulose production
in A. xylinum is roughly proportional to the rate of
cell growth. Cellulose production does not also depend on
net protein synthesis as evidenced by the capacity of the
washed cells to continue to synthesise cellulose even when
deprived of nitrogen source [43].
Without an inserted lacY