Molybdate recovery using immobilized bioengineered Saccharomyces cerevisiae

Molybdenum, a precious metal with important roles in industries, is projected to experience future shortage. Despite this, there is still no practical recycling process of this metal and around 25 thousand tons of molybdenum are discharged into wastewater annually. Biorecovery is a promising approach to resolve the above problem because of its high selectivity, high sensitivity, low running cost and low environmental burden. A bacterial molybdenum binding protein ModE has been constructed into yeast cells and named as ScBp5. In this study, the potential of genetic engineered yeast for recovering molybdenum from wastewater was further investigated. In order to stabilize the expression of ModE, strain ScBp5 was further modified by replacing promoter upstream of modE to generate ScBp6. The improvement of molybdenum adsorption efficiency by ScBp6 was confirmed especially in low concentration. The molybdenum isotherms parameters of ScBp6 was analyzed. To enable the usage as biorecovery agent in industrial settings, ScBp6 cells were immobilized using calcium alginate matrix, and the optimum immobilization conditions for ScBp6 were determined as 2% matrix density, 4 h of immobilization time, and 10 mg/ml cell density. The investigation of molybdenum adsorption kinetics by immobilized ScBp6 cells showed this adsorption was an efficient chemisorption. Overall, this research demonstrate the efficiency of immobilized yeast cell in molybdenum recovery.