I. Ananta et al., OXYGEN-TRANSFER AND CULTURE CHARACTERISTICS OF SELF-IMMOBILIZED SOLANUM AVICULARE AGGREGATES, Biotechnology and bioengineering, 47(5), 1995, pp. 541-549
Oxygen transfer characteristics of self-immobilized Solanum aviculare
cells were measured using aggregates 3.0 to 12.5 mm in diameter. Appar
ent specific oxygen uptake rates in the absence of external boundary l
ayers varied from 5.9 x 10(-7) to 8.5 x 10(-7) kg kg(-1) s(-1) dry wei
ght, but did not decline continuously with increasing particle size. T
he effective diffusivity of oxygen in deactivated aggregates increased
with particle diameter, varying from 5.0 x 10(-11) to 1.0 x 10(-9) m(
2) s(-1) or between 2% and 40% of the molecular diffusivity in water a
t the same temperature. Gas spaces detected in the larger aggregates w
ere confined to the central core and were not distributed throughout t
he tissue to facilitate Oxygen transfer. Oxygen consumption rates in t
he absence of diffusional limitations were estimated using the relatio
nship between the observable Thiele modulus and effectiveness factor f
or zero-order reaction. The calculated results indicated severe oxygen
limitations in the aggregates, but were inconsistent with the observa
tion that relatively large S. aviculare aggregates contained a high fr
action of viable cells and were capable of active growth and steroidal
alkaloid synthesis. This work suggests that oxygen delivery is facili
tated in living plant cell aggregates by mechanisms which depend on me
tabolic activity and which do not function in deactivated cells. (C) 1
995 John Wiley and Sons, Inc.