The enrichment of a specialized elemental sulfur–producing bacterium under extremely acidic condition

Abstract

In the gas biodesulfurization process, converting sulfides into elemental sulfur (S0) for reuse holds significant environmental, economic, resource, and social values. While the influence of pH on microbial community structure and enzyme activity is recognized, its effect on S0 yield has been underestimated. This study delves into how pH fluctuations affect the S0 yield in a biodesulfurization system. Under extremely acidic condition (pH < 1), the selectivity of S0 reached 90% even at high O2/H2S supply ratio of 1.8–2.1. Metagenomic analyses showed that as the pH decreased from neutral–alkaline to extremely acidic range, the dominant bacterium gradually shifted from Acidithiobacillus (37.0%), Acidiphilium (1.5%) and Thiomonas (1.2%), which possess complete sulfur metabolism (from sulfide to sulfate) genes, to Mycobacterium (79.2%) possessing the S0–synthesis gene (sqr) without the S0–oxidizing genes (ETHE1, sor, hdr, dsr and the Sox and S4I complex genes), resulting in a robust S0 yield in extremely acidic period. Various pathways for respiratory sulfur oxidation were present in different pH periods. The extremely acidic condition facilitated the selection of specific microorganisms by creating a highly selective environment, promoting the growth of acidophilic or acid-tolerant microorganisms with unique traits and altering the sulfur–metabolic pathways. These finding filled a knowledge gap regarding the impact of pH on sulfur–metabolic pathways and offered a new strategy for gaining S0.