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

• Published in: International biodeterioration & biodegradation 2016-09, Vol.113, p.238-243
• Main Authors: Ishak, Amir Fuhaira, Abdul Karim, Norsuhada, Ahmad, Wan Azlina, Zakaria, Zainul Akmar
• Format: Article
• Language: English
• Subjects: Acinetobacter; Beads; Chromate reductase; Cr(VI); Reduction
• ISSN: 0964-8305; 1879-0208
• DOI: 10.1016/j.ibiod.2016.03.020

Incomplete removal of chromium from discharge effluent of chromium-based industries is a serious problem due to its deleterious effect. ChromeBac™ 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 haemolyticusEF369508 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 m3 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 °C, in the presence of 1 mM Co2+ (highest) with Michaelis–Menten constant, Km and maximum reaction rate, Vmax of 184.47 μM 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™ process, hence reducing the time for overall Cr(VI) treatment process. •Negligible role of NADH during Cr(VI) reduction by bacteria.•Role of Co(II) ions to enhance Cr(VI) reduction.•Demonstration on the application of immobilized chromate reductase beads in an existing chromate treatment system.