Photosynthetic engineered living materials incorporating recombinant Chlamydomonas reinhardtii enable long-term semi-continuous photobiotransformation

Photosynthetic engineered living materials (ELMs) present an attractive platform for producing valuable compounds and fuels using solar energy. Compared to traditional suspension cultures, ELMs enable long-term biocatalytic activity, more efficient light utilization, and facilitate downstream processing. In this study, we developed photosynthetic ELMs by entrapping Chlamydomonas reinhardtii in either alginate or TEMPO-oxidized cellulose nanofibers (TCNF). The strain utilized was converting cyclohexanone to ε-caprolactone via photobiotransformation. The cell loading and matrix material were evaluated in short-term reactions and during a semi-continuous bioproduction in vials. We showed that the entrapped cells remain photosynthetically active and catalytically competent over extended periods. By replenishing the substrate and collecting the product every 24 h we achieved semi-continuous photobiotransformation for over two weeks, reaching an average productivity of 2.31 ± 0.26 g m−2 d−1 and accumulating 0.31 ± 0.03 mol m−2 corresponding to 3.49 ± 0.31 g L−1 of ε-caprolactone. These findings establish photosynthetic ELMs as a viable approach for long-term whole-cell photobiotransformation.