Heterologous expression of sulfur: quinone oxidoreductase (Sqr) to improve Thioalkalivibrio versutus D301 desulfurization performance

Abstract Aims Heterologous expression of sulfur: quinone oxidoreductase (Sqr) from Halomonas mongoliensis JS01, which is responsible for oxidizing sulfide to elemental sulfur, in Thioalkalivibrio versutus (T. versutus) D301 improves desulfurization. Methods and results We expressed sqr in T. versutus D301 by conjugative transfer and then assayed its desulfurization capacity in an airlift reactor and analyzed its transcriptome at −380 mV ORP. Our findings demonstrate that the D301-sqr+ strain, utilizing sodium sulfide as a sulfur source under optimal ORP conditions (−380 mV), achieved an elemental sulfur yield of 95%. This represents an 8% increase over the T. versutus D301. Moreover, the sodium sulfide utilization rate for D301-sqr+ showed a marked improvement [0.741 vs. 0.651 mmol∙(l·h)−1], with a concurrent increase in the rate of elemental sulfur production when compared to the T. versutus D301 (0.716 vs. 0.518 mmol ∙(l·h)−1). Transcriptome analysis revealed that the flavocytochrome c (fcc) and the sox system were differentially transcriptionally down-regulated in D301-sqr+ compared with the T. versutus D301. Conclusions Heterologous expression of the gene sqr altered the transcription of related genes in T. versutus D301 sulfur oxidation pathway, increasing the yield of elemental sulfur and the rate of sulfur oxidation, and making D301-sqr+ more potential for industrial applications.