The role of heterotrophic microorganism Galactomyces sp. Z3 in improving pig slurry bioleaching

The feasibility of removing heavy metals and eliminating pathogens from pig slurry through bioleaching involving the fungus Galactomyces sp. Z3 and two acidophilic thiobacillus (A. ferrooxidans LX5 and A. thiooxidans TS6) was investigated. It was found that the isolated pig slurry dissolved organic matter (DOM) degrader Z3 was identified as Galactomyces sp. Z3, which could grow well at pH 2.5-7 and degrade pig slurry DOM from 1973 to 942 mg/l within 48 h. During the successive multi-batch bioleaching systems, the co-inoculation of pig slurry degrader Galactomyces sp. Z3 and the two Acidithiobacillus species could improve pig slurry bioleaching efficiency compared to the single system without Galactomyces sp. Z3. The removal efficiency of Zn and Cu exceeded 94% and 85%, respectively. In addition, the elimination efficiencies of pathogens, including both total coliform and faecal coliform counts, exceeded 99% after bioleaching treatment. However, the counts of Galactomyces sp. Z3 decreased with the fall of pH and did not restore to the initial level during successive multi-batch bioleaching systems, and it is necessary to re-inoculate Galactomyces sp. Z3 cells into the bioleaching system to maintain its role in degrading pig slurry DOM. Therefore, a bioleaching technique involving both Galactomyces sp. Z3 and Acidithiobacillus species is an efficient method for removing heavy metals and eliminating pathogens from pig slurry.