Toxicity assessment upon augmented biostimulation source to indigenous rhizobium Cupriavidus taiwanensis

This novel-attempt study used chemostat pulse technique (CPT) and transient dynamics of dissolved oxygen (DO) in CSTR to quantify stimulating or inhibitory effects of augmented nutrient sources in the presence of phenol upon Cupriavidus taiwanensis R186. With injected augmented nutrients, phenol degradation performance of R186 was directly dependent on combined toxicity between phenol and the augmented substrate and the biodegradability of phenol. The findings indicated that although phenol was toxic to R186, all augmented nutrient sources still exhibited stimulating effects to bacterial growth of R186 in the presence of phenol. The simulating rankings of augmented nutrients were (1) at 200 mg/L, acetic acid > gluconic acid > yeast extract > glycerol ≫ phenol alone, (2) at 1000 mg/L, gluconic acid > acetic acid > glycerol > yeast extract ≫ phenol alone. This stimulating effect clearly suggested that this combined toxicity was antagonistic. It was also revealed that transient responses of DO seemed to be in parallel with the findings from CPT. It was thus concluded that substrate consumption patterns would play the most significant role in biostimulation to cultures with dual energy sources. This study can help uncover the mysteries of optimal biostimulation for phenol degradation as proposed in previous studies. In addition, this study directly provided a kinetic model to quantify the relative stimulation ranking of augmented nutrients in the presence of phenol for practical bioremediation.