Synergistic enzymatic mechanism of lepidolite leaching enhanced by a mixture of Bacillus mucilaginosus and Bacillus circulans

• Published in: The Science of the total environment Vol. 947; p. 174711
• Main Authors: Xu, Chao, Zhao, Xingqing, Duan, Huaiyu, Gu, Wei, Zhang, Du, Wang, Rucheng, Lu, Xiancai
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.10.2024
• Subjects: Bacillus circulans; Bacillus mucilaginosus; bioleaching; Co-bioleaching; coculture; environment; Enzymatic hydrolysis; humic acids; Lepidolite; metabolism; microbial communities; polysaccharides; secretion; Silicate bacteria; silicates; symbiosis; synergism; Synergistic effect; Lepidolite; Synergistic effect; Enzymatic hydrolysis; Co-bioleaching; Silicate bacteria
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.174711

Numerous studies have demonstrated that the co-leaching of ores by different silicate bacteria significantly improves the performance of bioleaching systems. Nevertheless, the mechanism of different silicate bacteria synergistically or complementarily enhanced the leaching process of lithium-containing silicate remains unclear. This study discussed the leaching impact of the combined presence of two metabolically distinct silicate bacteria on lepidolite, with the aim of comprehending the synergistic effect resulting from the presence of Bacillus mucilaginosus and Bacillus circulans in the leaching process. The results indicated that the polysaccharides and proteins secreted by bacteria-containing functional groups such as -OH and -COOH, which played an important role in the complex decomposition of ores. Organic acids played the role of acid etching and complexation. Bacillus mucilaginosus and Bacillus circulans exhibited low individual leaching efficiency, primarily due to their weak organic acid secretion. Moreover, the prolific polysaccharide production by Bacillus mucilaginosus led to bacterial aggregation, diminishing contact capability with minerals. Bacillus circulans decomposed the excessive polysaccharides produced by Bacillus mucilaginosus through enzymatic hydrolysis in the co-bioleaching process, providing later nutrient supply for both strains. The symbiosis of the two strains enhanced the synthesis and metabolic capabilities of both strains, resulting in increased organic acid secretion. In addition, protein and humic acid production by Bacillus mucilaginosus intensified, collectively enhancing the leaching efficiency. These findings suggested that the primary metabolic products secreted by different bacterial strains in the leaching process differ. The improvement in bioleaching efficiency during co-leaching was attributed to their effective synergistic metabolism. This work contributes to the construction of an efficient engineering microbial community to improve the efficiency of silicate mineral leaching, and reveals the feasibility of microbial co-culture to improve bioleaching. [Display omitted] •The co-cultivation of strains BM and BC exhibited a synergistic effect.•Strain BC hydrolyzed the polysaccharides produced from BM by enzymatic mechanisms.•Mixed culture enhanced the metabolic capacity.•Synergistic interaction between strains BM and BC improved the leaching effect.