Phenol degradation and production of PHA using phenol degradation products as substrates

Polyhydroxyalkanoates (PHAs), which are alternatives to plastics, are derived from microorganisms and are environmentally friendly due to their biodegradable nature. However, they typically have high production costs. Therefore, the conversion of low-cost harmful substances into high-value-added products such as PHA represents a promising approach to potentially reducing production costs. Phenol is one of the organic pollutants found in industrial wastewater. It is discharged by producers in industries such as textile processing, petroleum, pharmaceuticals, and resins. Even at low concentrations, phenol exhibits strong toxicity to all forms of life and is classified as a priority pollutant by the U.S. Environmental Protection Agency (EPA). Therefore, this study targeted phenol as the substance of interest. This study employed a two-stage process for PHA production. In the first stage, phenol degradation by the phenol-degrading bacterium Comamonas sp. C1 was conducted, and in the second stage, PHA was produced by Bacillus sp. CYR1 using phenol degradation products as substrates. Phenol (500 mg/L) was repeatedly added three times in a conical flask, resulting in the production of 2000 mg/L of phenol degradation products. These degradation products were added to the media, adjusted to pH 7, sterilized, and used as PHA production media. Results showed an increase in pH under all conditions, possibly due to the consumption of organic acids such as cis,cis-muconic acid, which is generated during phenol degradation. PHA production of 54.5 mg/L with a PHA yield of 30.2% was observed, suggesting that the conversion of harmful phenol degradation products to PHA is feasible.