Polycyclic aromatic hydrocarbons (PAHs) are hazardous organic contaminants for which microbial bioaugmentation is a promising remediation strategy, but poor persistence of introduced microorganisms can limit efficacy. Encapsulation in biodegradable carrier materials may improve persistence by protecting cells from environmental stress while enabling controlled release. However, the influence of capsule design, microbial species, and environmental conditions on encapsulation performance remains poorly understood. We evaluated alginate encapsulation of the PAH-degrading bacteria Pseudomonas putida and Novosphingobium aromaticivorans across different nutrient conditions and capsule formulations. Encapsulation effects varied by species and medium, influencing growth rate, maximum cell density, overall growth, and lag time. Methods used to quantify encapsulated cells also affected apparent cell recovery, highlighting the importance of enumeration approach. Encapsulation had no effect on the long-term viability of P. putida but resulted in increased concentrations of N. aromaticivorans. Capsule composition further influenced cell retention: increasing alginate enhanced cell retention within the capsule, while chitosan coatings reduced cell concentrations within capsules without affecting external concentrations. These findings demonstrate that the benefits of microbial encapsulation are species- and environment-dependent and that capsule formulation can be tuned to influence bacterial persistence and release, providing design principles for developing encapsulated microbial inoculants for bioaugmentation applications.
