Biosorption and biodegradation of pyrene by Brevibacillus brevis and cellular responses to pyrene treatment

• Transmembrane transport, accumulation and degradation contributed to pyrene removal.
• Regrowth of cells during pyrene degradation was observed by TruCOUNT assay.
• Pyrene increased cell viability to a certain extent.
• Pyrene decreased both cell size and intracellular particle density.

Biodegradation has been proposed as an effective approach to remove pyrene, however, the information regarding cellular responses to pyrene treatment is limited thus far. In this study, the biodegradation and biosorption of pyrene by Brevibacillus brevis, along with cellular responses caused by pollutant were investigated by means of flow cytometry assay and scanning electron microscopy. The experimental results showed that pyrene was initially adsorbed by B. brevis and subsequently transported and intracellularly degraded. During this process, pyrene removal was primarily dependent on biodegradation. Cell invagination and cell surface corrugation occurred due to pyrene exposure. Nevertheless, cell regrowth after 96 h treatment was observed, and the proportion of necrotic cell was only 2.8% after pyrene exposure for 120 h, confirming that B. brevis could utilize pyrene as a sole carbon source for growth. The removal and biodegradation amount of pyrene (1 mg/L) at 168 h were 0.75 and 0.69 mg/L, respectively, and the biosorption amount by inactivated cells was 0.41 mg/L at this time.