2.3 Analytical methods
Pigment production was spectrophotometrically
monitored every 48 h in aseptic conditions. A sample
of 3 ml of culture medium was carefully taken. Some
samples were previously centrifuged at 10 000 r/min
for 5 min to remove suspended cells and all samples
were filtered using 0.45-μm sterile membranes.
Pigment production was measured at 500 nm
(Méndez-Zavala et al., 2007), and pH and reduction/
oxidation potential (p-Redox) were determined potentiometrically.
Biomass was determined gravimetrically
(dry weight) after the incubation at 60 °C. A
portion of mycelium was used for microscopic observations.
The yield of product per unit biomass (YP/X)
was calculated as the ratio of the amount of pigment
produced (Pt−P0) in a certain time (t) to the biomass
generated in the same time (Xt−X0).
2.4 Statistical analysis
The results were evaluated in triplicate using a
divided parcel design with a factorial fix 2×3, and the
analysis was performed using the Statistical Program
Infostat (Córdoba, Argentina).