Bioconversion of cultivated-meat spent medium by Brevibacillus fluminis SLAM AEPS10 links remediation with poly(3-hydroxybutyrate) production

Cultivated-meat spent medium (CSM) is an emerging mammalian cell culture waste stream containing residual organic carbon, ammonium, lactate, proteins, and metabolites. Treatment strategies that connect pollutant removal with resource recovery are needed to reduce the environmental burden of CSM management. This study aimed to identify a bacterium that links CSM remediation with poly(3-hydroxybutyrate) (PHB) production. Screening of 29 rumen isolates identified Brevibacillus fluminis SLAM AEPS10 based on CSM growth, polymer recovery, and methyl 3-hydroxybutyrate detection. During 72 h of cultivation in CSM, AEPS10 retained 86.71% viability and reduced biochemical oxygen demand, total organic carbon, and ammonium by 77.8%, 62.7%, and 46.5%. The recovered polymer was identified as a PHB homopolymer by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. AEPS10 produced 15.83 mg/L PHB and accumulated an average of 6.51 intracellular granules per cell, confirming cellular PHB storage during CSM cultivation. Compared with a strain that grew in CSM but did not produce PHB, AEPS10 uniquely carried phaC and phaQ within a gene cluster arranged in the order fabG, phaC, phaQ, and fabG , consistent with a Class IV PHA synthase system. These findings establish AEPS10-mediated CSM conversion as a single bacterial process linking remediation with intracellular PHB recovery.