. Biocatalyst characterization
The mass of cells immobilized onto the support particles were
quantified as dry cell weight as follows. Carrier prepared for fermentation
was placed on a filter paper to remove fluid. The cells
immobilized onto the carrier, without extra medium, were pressed
out using a glass stick, washed with sterilized distilled water, and
the support was dried at 105 C up to constant weight. The dry
weight of the immobilized cells in the collected liquid was calculated
by measuring the optical density at 660 nm, using a spectrophotometer
(Carl Zeiss, Jena, Germany). A previously constructed
calibration curve was used to relate the optical density measurements
to dry cell concentration in the samples. Maize stem ground
tissue recovered from the cell-free medium was dried to measure
water retention capacity and also used as a control to avoid any
interference in weighing and optical density measurements.
2 R. Razmovski, V. Vucˇurovic´ / Fuel 92 (2012) 1–8
Weighing of dried maize stem ground tissue was accomplished
using an analytical balance.