Searching of Phenol-Degrading Bacteria in Raw Wastewater from Underground Coal Gasification Process as Suitable Candidates in Bioaugmentation Approach

The aim of the conducted study was to isolate, identify and characterize suitable bacterial strains from UCG waste-water as potential candidates for the bioaugmentation approach. For this purpose, the straightforward cultivation procedure and unique biochemical selection were employed to gain insights into the specific properties of bacteria. From the 100 strains isolated from UCG wastewater, three (Paenibacillus pasadensis SAFN-007, Peanibacillus humicus Au34, and Staphylococcus warneri DK131) demonstrated the capacity to degrade phenol and specific biochemical properties. Phenol degradation reached more than 90% for the above-mentioned strains, while the av-erage phenol removal rate for other selected strains was 82.9%, ranging from 66.1% to 90%. The bacterial strains belong to multi-enzyme producers and constitute a possible source of potential technologically important en-zymes. Phenotypic microarray plates were used to characterise the metabolic properties of the strains. It was found that 74%, 67.4% and 94.2% of the carbon metabolites tested were utilised by Paenibacillus pasadensis SAFN-007, Peanibacillus humicus Au34 and Staphylococcus warneri DK131, respectively. Among C sources, the strains have the capability to metabolize some substrates appearing in phenol pathways, such as: N-acetyl-D-glucosamine, succinic acid, alpha-hydroxy-glutaric acid-gamma-lactone, bromosuccinic acid, mono-methyl succinate, methyl-pyruvate, p-hydroxy-phenyl acetic acid, m-hydroxyphenylacetic acid, L-galactonic acid-gamma-lactone, D-galactonic acid-gamma-lactone, phenylethylamine. Bacteria show different levels of tolerance to pH and osmolality, and they can thrive in different habitats. Another characteristic of these strains is their high resistance to many antibiotics (multi-resistant bacteria). These properties allow the use of the isolated bacterial strains as good candidates for bioremediation of phenol-contaminated environments. The wastewater from the underground coal gasification process is an example of a good extreme environment for the isolation of unique bacteria with specific metabolic properties.