Enzyme‐Modulated Anaerobic Encapsulation of Chlorella Cells Allows Switching from O₂ to H₂ Production

Abstract

Single‐cell encapsulation has become an effective strategy in cell surface engineering; however, the construction of cell wall‐like layers that allow the switching of the inherent functionality of the engineered cell is still rare. In this study, we show a universal way to create an enzyme‐modulated oxygen‐consuming sandwich‐like layer by using polydopamine, laccase, and tannic acid as building blocks, which then could generate an anaerobic microenvironment around the cell. This layer protected the encapsulated C. pyrenoidosa cell against external stresses and enabled it to switch from normal photosynthetic O2 production to photobiological H2 production. The layer showed an smaller effect on the PSII activity, which contributed a significant enhancement on the rate (0.32 μmol H2 h−1 (mg chlorophyll)−1) and the duration (7 d) of H2 production. This strategy is expected to provide a pathway for modulating the functionality of cells and for breakthroughs in the development of green energy alternatives.

Photosynthetic hydrogen production by droplet-based microbial micro-reactors under aerobic conditions

“…Given that hydrogenase activity is induced in Chlorella cells under hypoxic photosynthetic conditions 26 , 27 , we investigated whether the algal cells confined within the core of the spheroids could also utilize photosynthetic electrons for hydrogen production in air to produce microbial micro-reactors with dual functionality. As Chlorella cells located in the surface and near-surface regions of the spheroids retained their photosynthetic oxygen productivity, we used larger spheroids (mean size, 92 μm) to maximise the levels of evolved hydrogen from the micro-niche in the core of the multicellular micro-reactors (Fig.…”

“…The procedure is facile and capable of high throughputs for modulating algal cell functionality towards hydrogen production without impairing the viability of the living cells. Moreover, it should be possible to combine our methodology with more complex bioengineering approaches involving sulfur deprivation 24 , genetically modified oxygen-tolerant [FeFe]-hydrogenases 25 or cellular surface modifications 27 . Compared with synthetic hydrogen-producing systems 30 , the limited rates and yields in the multicellular spheroids remain challenging aspects of future work.…”

“…The capture of large numbers of cells in each w/w emulsion droplet occurs spontaneously and at high efficiency to generate a suspension of droplet-based algal colonies that are subsequently hyperosmotically compressed into closely packed multicellular spheroids. We show that the dual photosynthetic behaviour originates from the onset of a hypoxic micro-niche within the interior of the spheroids such that the production of oxygen and hydrogen (via hydrogenases 24 – 27 ) occurs respectively at the surface or within the core of the dispersed bioreactors. We develop the methodology to fabricate microbial micro-reactors comprising spatially segregated communities of algal and non-photosynthetic bacterial cells that operate synergistically through the interplay of hypoxic photosynthesis and aerobic respiration to enhance the level of hydrogen production under air (Fig.…”

A Removable Artificial Cell Wall for Withstanding Ciprofloxacin

“…Cell surface engineering technology has been employed to construct protective layer clothing for the encapsulated cells, which improved the viability of cells abnormal environments. [ 30,31 ] In this study, the encapsulated S. cerevisiae cells in situ against ciprofloxacin was achieved via putting on and taking off a wearable protective layer clothing. To generate the protective layer clothing, the artificial cell wall was self‐assembled on the surface of S. cerevisiae cells by using the positively charged CMCS (zeta potential = 17.0 mV) and negatively charged DEX‐COOH (zeta potential = ‐13.5 mV) as the building blocks.…”

Organism–Materials Integration: A Promising Strategy for Biomedical Applications

“…For example, Huang and co‐workers fabricated a sandwich‐like structure on the surface of Chlorella pyrenoidosa cells. [ 41 ] First, a PDA layer was coated onto the cells through oxidative polymerization. This layer acting as a “bridge” can connect the cells and promote the formation of hydrogen bonds by interacting with thiol or amine moieties of laccase.…”