Analysis of microbial community potentially involved in carbon monoxide production in compost and its functional assessment: Utilized pathways, enzymes, and genes

Carbon monoxide (CO) is a valuable compound widely used in industry, and its biological production aligns with the bioeconomy principles. This study introduces a novel perspective by exploring biowaste composting as a potential source of CO production. Using 16S rDNA sequencing, microbial communities within two zones of a compost pile, with low (CO/L, 119 ppm) and high CO concentration (CO/H, 785 ppm), were characterized. The metabolic potential of microbial communities was investigated using PICRUSt2, an advanced tool for functional analysis. Results revealed higher alpha diversity in CO/H samples compared to CO/L, likely influenced by the lower temperature at the CO/H sampling site (50 °C vs. 62 °C in CO/L). Importantly, in the PCoA plots, samples clustered together depending on the sampling site. The microbial community composition was dominated by Bacilli (up to 98.8 % and 55.4 % of CO/L and CO/H samples, respectively). One of the key results was the detection of the Wood–Ljungdahl pathway, a metabolic route for CO production, in nearly all compost samples. This pathway was more abundant in CO/H samples (0.011–0.027 %) compared to CO/L samples (0.000–0.002 %). Moreover, 7 enzymes and 7 genes responsible for CO production and metabolism were detected in compost samples, suggesting that the observed CO formation is likely of biotic origin. The study for the first time underscored the potential of composting as a sustainable method for CO generation and validated PICRUSt2 as a reliable tool for uncovering biotic CO production mechanisms, offering valuable preliminary insights into the functional capabilities of microbial communities.