In this work, we aimed at improved viability and growth of the microalga Chlamydomonas reinhardtii in transparent silica hydrogels based on low-ethanol, low-sodium and low-propylamine synthesis. Investigation into replacement of conventional base KOH by buffers dipotassium phosphate and tris(hydroxymethyl)aminomethane along with increased precursor concentrations yielded an aqueous synthesis route which provided a gelation within 10 min, absorptions below 0.1 and elastic moduli of 0.04-4.23 kPa. The abrasion resistance enhanced by 41% compared to calcium alginate hydrogels and increased to 70-85% residual material on addition of chitosan. Entrapment of microalgae in low-sodium and low-propylamine silica hydrogels maintained the PSII quantum yield above 0.3 and growth rates of 0.23 ± 0.01 d-1, similarly to cells entrapped in calcium alginate. These promising results pave the way for the entrapment of sensitive, photosynthetically active and growing cells for in robust biotechnological applications.
Keywords: Mechanical stability; Microalgae; Photosynthetic activity; Silica hydrogels; Transparency.
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