Production and Formulation of Alcanivorax borkumensis SK2 Cell Powders for Marine Oil Spill Bioremediation

Oil spills pose severe threats to marine ecosystems and coastal communities. Alcanivorax borkumensis SK2, a marine bacterium with superior hydrocarbon-degrading capabilities, emerges as a promising agent for bioremediation. This study identified an economical growth substrate for A. borkumensis SK2 and led to highly viable cell powder formulations for effective applications in contaminated marine environments. Various non-hydrocarbon substrates were evaluated to replace the costly sodium pyruvate, revealing that canola oil and sunflower oil gave biomass levels (optical density) four times higher than sodium pyruvate (20 ± 2 and 20 ± 1, compared to 4.6 ± 0.4, respectively). Freeze-drying and spray-drying approaches were investigated to produce a viable cell formulation. Two screening campaigns of potential freeze-drying cryoprotectants showed that the proprietary blend of Proventus Bioscience Inc. (Proventus) and 0.5 M glutamate ensured the highest viability, with 2 ± 1×10¹⁰ and 1.1 ± 0.3 × 10¹⁰ CFU/g, after the first screening, and 1.0 ± 0.5 × 10¹⁰ and 6 ± 2 × 10⁹ CFU/g after the second screening. Differential scanning calorimetry (DSC) analysis demonstrated a 9%-15% reduction in ice formation with cooling rates from 5 to 10°C/min. Glutamate reduced ice formation by 5%-9% compared to Proventus' solution. To promote cell viability during A. borkumensis SK2 freezing and freeze-drying, the best product temperatures were determined to be -65°C with 0.5 M glutamate and -59°C with Proventus' blend. Spray-drying resulted in cell powders with a viability up to 1.0 ± 0.7 × 10⁵ CFU/g, considerably lower than the levels obtained by freeze-drying, indicating some potential but also the need for further research and optimization.