Enhancement of Bioleaching Using AHL Mediated Quorum Sensing

Abstract

Biomining is a maturing technology that uses the activity of sulfur and iron oxidising microorganisms to liberate valuable metals from ores but suffers from slow reaction kinetics. Increasing the reaction kinetics of a biomining process could produce significant bottom line improvements for mining companies worldwide and encourage the use of biomining as a green mining technology. Quorum sensing molecules have been shown to successfully modulate the behaviours of biomining bacteria in manners that may be able to improve bioreactor retention times. This study tests the potential for two different quorum sensing treatments to improve the nickel leaching ability of a biomining bacterial consortium. A novel method of delivering quorum sensing treatments to bacterial cultures is described while doubt is cast on established methods. Laboratory scale bioreactors were constructed and the leaching of nickel into solution was followed via ICP-AES to quantify improvements in bioleaching ability. Similar bioreactors were used to exhibit the inhibitory effect that a commonly used organic solvent can have on the leaching ability of bioleaching consortia. Ultimately a qualitative improvement in the bioleaching of nickel is produced using a mixture of tetradecanoyl-acylhomoserine lactone (C14-AHL) and its two derivatives, but the use of C14-AHL alone did not improve bioleaching kinetics. Use of small volumes of the solvent DMSO produced large inhibitory effects on the leaching of nickel by bioleaching consortia.