Chromate detoxification using combination of ChromeBac™ system and immobilized chromate reductase beads

Incomplete removal of chromium from discharge effluent of chromium-based industries is a serious problem due to its deleterious effect. ChromeBac (TM) is a locally developed Cr(VI) reduction system carried out by aerobic Cr(VI) resistant bacteria followed by chemical precipitation. The locally isolated Cr(VI) resistant-reducing Acinetobacter haemolyticus EF369508 was immobilized onto carrier materials inside a 50 L bioreactor. Mixture of 10% (v/v) liquid pineapple waste and neutralized Cr(VI) solutions (30 -60 mgL(-1)) was fed into the bioreactor at 0.11 m(3) h(-1). Around 90% of the initial Cr(VI) was reduced after 24 h of contact inside the bioreactor. Residual Cr(VI) was then further reduced to between 1.0 and 1.5 mgL(-1) by immobilized chromate reductase alginate-beads packed in a 10 L flow-through column, after 15 h of contact. Some important characteristics for the chromate reductase activities for A. haemolyticus are as follows; not NADH-dependent, associated with CFE with notable contribution from the membrane fraction, enhanced in the presence of glucose, optimal at pH 7.0, 30 degrees C, in the presence of 1 mM Co2+ (highest) with Michaelis-Menten constant, K-m and maximum reaction rate, V-max of 184.47 mu M and 33.3 nmol/min/mg protein respectively. Ag+ and Hg2+ inhibited the enzyme activity. This study demonstrated the potential of using immobilized chromate reductase beads to further reduce residual Cr(VI) present in the effluent of a ChromeBac (TM) process, hence reducing the time for overall Cr(VI) treatment process. (C) 2016 Elsevier Ltd. All rights reserved.