Assessment of the Acidithiobacillus system upon microencapsulation with Arabic gum for its application in the mineral...

Bio-metallurgical processes provide interesting alternatives to critical issues that affect the mining industry, namely, the recovery of metals of interest and bioremediation of contaminated soils and waters. There is a wide variety of microorganisms related to mining activities; however, bio-metallurgical processes impact on industrial processes is not high, mainly due to two reasons: the costs of monitoring metabolic activities and the genetic stability of bacteria during long process times. This research presents a novel strategy for the manipulation of microorganisms, with economical and simple methods for application, conservation, and storage stages. Microencapsulation using Arabic gum (AG) of the bacteria consortium of Acidithiobacillus ferrooxidans (Af) and Acidithiobacillus thiooxidans (At) by spray-drying (SD) is proposed for mineral industrial applications. In this work, the viability, leaching and structural properties of the microcapsules are evaluated. Yields higher than 90% reveal optimum spray drying conditions for encapsulation. The powder properties (water activity ≤ 0.3, humidity ≤ 9 % and pH ≤ 3.0) ensure stability upon storage, with fast release profiles (<2 h) reducing bioleaching time. Scanning electron microscopy reveals smooth spherical particles with modal distribution, which preserves mechanical stability under flow. No changes in the functional groups of the biopolymers upon SD indicates bacteria encapsulation, wherein Arabic gum provides a protective shield to bacterial culture through acid hydrolysis with high viability (93%). Preservation of the leaching properties of the bacteria after three years is ensured.