Pigment production in extracts obtained from P.
purpurogenum GH2 following different treatments
is shown in Table 2. The reddest culture medium
was achieved with treatment T1 as a result of the
highest pigment production, which was 2.46 g/L at
240 h. The color present in the extract was influenced
by the initial pH of the culture medium. Gunasekaran
and Poorniammal (2008) also found that the initial pH
has a strong effect on red pigment production by
Penicillium sp., but in that case the highest product
accumulation was reached at an initial pH of 9.0.
Chen and Johns (1993) in a study of a Monascus
purpureus culture demonstrated the presence of yellow
pigments (ankaflavin) at a low pH (4.0) and red
pigments (monascorubramine) at higher pH (6.0),
contrary to the results obtained in our research. Other
authors (Lin and Demain, 1991; Orozco and Kilikian,
2008) found a positive effect on cellular growth due
to the pH of the culture medium, favoring the production
of red pigments intracellularly and extracellularly
(secondary metabolites) at a pH of 5.5, as
shown in our study. These results suggest that pH can
affect the activities of enzymes involved in the biosynthesis
of pigments, but the effect depends on the
particular microorganism utilized.