Engineering an agrowaste-based multilayer bio-encapsulation system for sustained nutrient release and microbial biotransformation of chlorinated solvents

Trichloroethylene (TCE), a known carcinogen, is denser than water, which explains its deep presence in groundwater. Limitations on long-term supplies of TCE degraders and nutrients often led to TCE dichlorination failures in the field. This study presents the development and evaluation of an agrowaste-based multilayer bioencapsulation system designed to prolong microbial activity and enhance nutrient availability for a more favorable TCE-dechlorination environment. TCE-degrading consortia were integrated with a nutrient-rich core derived from recycled fermented agrowastes and encapsulated within a structurally reinforced sodium alginate matrix to form bio-pellets. The acclimated microbial community exhibited a degradation rate constant of 0.33 day⁻¹, with confirmed transformation of TCE into dichloroethylene and vinyl chloride, indicating active reductive dechlorination pathways. Characterization of the encapsulated system revealed a nutrient profile of 410.4 ± 29.7 mg TOC g⁻¹, 9.1 ± 0.2 mg TN g⁻¹, and 20.5 ± 0.7 mg TP g⁻¹, which enabled sustained nutrient release to support microbial metabolic functions. Column reactor experiments demonstrated that the multilayer structure maintained physical integrity and functional stability for more than 74 days. The system achieved a total TCE removal efficiency of 98.5%, reducing concentrations from 600 mg L⁻¹ to 9.1 mg L⁻¹, while effectively alleviating mass transfer limitations commonly observed in non-encapsulated systems. Although microbial activity induced localized acidification, the incorporation of natural buffering capacity helped maintain system stability. These results demonstrate that the proposed bio-encapsulation platform provides a framework for integrating material design with microbial function, offering promising applications in environmental biotechnology and bioprocess engineering.