Abstract
The algal cell immobilization is a commonly used technique for treatment of waste water, production of useful metabolites and management of stock culture. However, control over the size of immobilized droplets, the population of microbes, and production rate in current techniques need to be improved. Here, we use drop-on-demand inkjet printing to immobilize spores of the alga Ecklonia cava within alginate microparticles for the first time. Microparticles with immobilized spores were generated by printing alginate-spore suspensions into a calcium chloride solution. We demonstrate that the inkjet technique can control the number of spores in an ejected droplet in the range of 0.23 to 1.87 by varying spore densities in bioink. After the printing-based spore encapsulation, we observe initial sprouting and continuous growth of thallus until 45 days of culture. Our study suggest that inkjet printing has a great potential to immobilize algae, and that the ability to control the number of encapsulated spores and their microenvironments can facilitate research into microscopic interactions of encapsulated spores.
Highlights
Immobilization of algal cells in polymeric hydrogels has a range of applications
Ecklonia cava is an edible, perennial marine brown alga (Laminariales, Phaeophyta) that grows in the ocean around South Korea and Japan[15]
The DOD piezoelectric inkjet printing uses a piezoelectric actuator in the channel of the nozzle of piezoelectric inkjet printer
Summary
Immobilization of algal cells in polymeric hydrogels has a range of applications. Immobilized algal cells can be used for effluent treatment to remove nutrients, metals and industrial pollutants[1,2]. Methods to entrap microorganisms in hydrogel particles include conventional dripping of cell suspension into a receptacle that contains hardening solution[11]; extrusion dripping[12]; gravity-driven dripping[13]; and suspension spraying[14]. All of these methods are either slow or not allow sufficient control over the size of droplets, their content of microbes or production rate. Piezoelectric inkjet printing can generate droplets of size 1–100 pL at >10 kHz. The size of the ejected droplet can be controlled by adjusting the input voltage pulse or by selecting an appropriate nozzle and be smaller than the diffusion limits of nutrients and metabolites in hydrogels (100– 200 μm)[12]. Since alginates are mainly isolated from microalgae including E. cava, alginate was selected as a polymer for immobilizing E. cava spores with the inkjet printing technique
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