Isolation and identification of carbon monoxide producing microorganisms from compost

[Display omitted] •The biological CO production in the compost pile was carried out by bacteria.•Bacteria isolated from compost produced CO with concentration > 1000 ppm.•The most common genus in compost was Bacillus with four representatives.•B. paralicheniformis and B. licheniformis produced the highest concentrations of CO.•High CO concentrations were accompanied by low O2 (8%) Carbon monoxide (CO) formation has been observed during composting of various fractions of organic waste. It was reported that this production can be biotic, associated with the activity of microorganisms. However, there are no sources considering the microbial communities producing CO production in compost. This preliminary research aimed to isolate and identify microorganisms potentially responsible for the CO production in compost collected from two areas of the biowaste pile: with low (118 ppm) and high CO concentration (785 ppm). Study proved that all isolates were bacterial strains with the majority of rod-shaped Gram-positive bacteria. Both places can be inhabited by the same bacterial strains, e.g. Bacillus licheniformis and Paenibacillus lactis. The most common were Bacillus (B. licheniformis, B. haynesii, B. paralicheniformis, and B. thermolactis). After incubation of isolates in sealed bioreactors for 4 days, the highest CO levels in the headspace were recorded for B. paralicheniformis (>1000 ppm), B. licheniformis (>800 ppm), and G. thermodenitrificans (∼600 ppm). High CO concentrations were accompanied by low O2 (8%). It is recommended to analyze the expression of the gene encoding CODH to confirm or exclude the ability of the identified strains to convert CO2 to CO.