Isolation and application to wastewater treatment of Pseudomonas sp. No. 44 possessing high formaldehyde tolerance

Bacteria and fungi that are resistant to formaldehyde (FA) are expected to use biochemical processing to degrade FA in wastewater. Pseudomonas sp. No. 44, which carries the FA dismutase and several FA dehydrogenase genes, was isolated from industrial wastewater as an FA-degrading strain that did not match the genome sequence of any previously reported FA-degrading bacteria. While maintaining a low cell density (OD₆₀₀ = 0.1), almost all the FA (1 g L⁻¹) was degraded within 6 h, after which cell proliferation predominated. Furthermore, increasing the cell density to OD₆₀₀ = 1.0 maintained high FA resistance and rapid degradation performance within 3 h, even at concentrations as high as 5 g L⁻¹. Formic acid, which temporarily increased in concentration as the FA decomposed, disappeared as the culture progressed, suggesting that this strain also exhibited high formate dehydrogenase activity. This practical performance exceeded that of any reported FA-degrading microorganism, including fungi. Vacuum-dried bacterial cells exhibited FA decomposition properties at the same level as those of live cells in the presence of phosphate due to the maintenance of enzymatic activity. The dried bacterial cells of strain No. 44, which are easy to handle and store, are expected to allow the maintenance of FA concentration in wastewater below the emission regulation concentration for each region through the addition of the strain at appropriate intervals.