Microbiological versus Chemical Reductive Sulfidation: An Experimental and Theoretical Study

Area of Science:

• Biochemistry
• Organic Chemistry
• Microbiology

Background:

• Microbiological reductive sulfidation (RS) is an understudied but efficient method for thiol synthesis.
• The sulfate-respiring bacterium Desulfovibrio sp.86 exhibits RS activity.
• Previous work demonstrated its ability to transform the pesticide chlordecone.

Purpose of the Study:

• To evaluate the substrate range of Desulfovibrio sp.86 for RS using 28 carbonyl compounds.
• To compare the mechanisms of microbiological RS with chemical RS.
• To rationalize observed trends using experimental and theoretical analyses.

Main Methods:

• Tested 28 carbonyl compounds for bacterial RS using Desulfovibrio sp.86.
• Investigated chemical RS using phosphorus pentasulfide (P4S10) and a designed protocol for direct thiol conversion.
• Employed density functional theory (DFT) calculations to analyze structural, electronic, and thermodynamic parameters.

Main Results:

• Chemical RS of some carbonyls with P4S10 directly yielded thiols, suggesting a single-electron transfer mechanism.
• Desulfovibrio sp.86 transformed various aldehydes and ketones into thiols without forming thiones.
• Bacterial RS of aldehydes correlated with bacterial growth, unlike chemical RS.

Conclusions:

• Microbiological and chemical RS likely proceed via distinct pathways.
• The selectivity differences offer potential for novel applications in organic synthesis.
• Desulfovibrio sp.86 demonstrates versatility in biotransforming carbonyls to thiols.