The role of sulfate as a competitive inhibitor of enzymatically-mediated heavy metal uptake by Citrobacter sp: implications in the bioremediation of acid mine drainage water using biogenic phosphate precipitant
P. Yong et Le. Macaskie, The role of sulfate as a competitive inhibitor of enzymatically-mediated heavy metal uptake by Citrobacter sp: implications in the bioremediation of acid mine drainage water using biogenic phosphate precipitant, J CHEM TECH, 74(12), 1999, pp. 1149-1156
Heavy metals can be removed from solution via biocrystallization with enzym
atically liberated inorganic phosphate, according to Michaelis-Menten kinet
ics, in free whole cells and cells immobilized within polyacrylamide gel in
a flow-through reactor. Sulfate is a competitive inhibitor of phosphate re
lease and a predictive model was developed and shown to describe the effect
of sulfate on the efficiency of phosphate release by flow-through columns.
The inhibitory effect was substantially less than anticipated in the case
of metal removal by the columns. In the case of lanthanum removal metal rem
oval efficiency was restored by increasing the substrate concentration in a
ccordance with model predictions. In the case of uranyl ion its removal wit
h an equivalent substrate supplement increased the activity by 20% over the
initial value at a limiting flow rate. Since the initial loss in activity
in the presence of 40 mmol dm(-3) SO42- (approximately twice the K-i value)
was only approximately 20% with both metals this was considered to be a mi
nor problem for bioprocess application. In confirmation, calculations made
from a published 'case history' of application of the system to the bioreme
diation of acid mine drainage water (AMD) containing 0.22 mmol dm(-3) of ur
anyl ion and 35mmoldm-3 of SO42- showed that the benchscale model is a good
representation of performance under actual load conditions. (C) 1999 Socie
ty of Chemical Industry.