Green and sustainable production of high value compounds via a microalgae encapsulation technology that relies on CO₂as a principle reactant

Abstract

Title: Green and sustainable production of high value compounds via a microalgae encapsulation technology that relies on CO 2 as a principle reactant This research article highlights the extraordinarily long-term viability and high activity of microalgae entrapped within an alginate-silica hybrid matrix, holding much promise for the design of new generation fi xed biomass photobioreactors that are based on microencapsulation technology. This bionanotechnology opens up exciting avenues for the design of photosynthetic solar cells and artifi cial trees for a green and sustainable production of high value compounds and electricity on the basis of photosynthesis process.A very promising and facile one-pot synthesis pathway is presented for the microencapsulation of live cells in a very porous core-shell system based upon a robust matrix. (Alginate-SiO 2 -polycation)shell@(alginate-SiO 2 ) core hybrid beads, on the millimeter scale, containing live cells are obtained through cross-linking chemistry and the polycondensation of silicic acid in conjunction with the use of a polycation to negate the surface charge on silica. Very interestingly it is revealed that the polycation used (PDADMAC) plays a very important role in the formation of highly robust core-shell beads. PDADMAC acts as a catalyst in the polycondensation of silicic acid, leading to the formation of a resistant double layer shell comprising of an interior layer of alginate-SiO 2 with a very homogeneous distribution of porous SiO 2 and an external layer of porous PDADMAC that confines SiO 2 within the bead. The photosynthetic chlorophyta Dunaliella tertiolecta, which produces high value metabolites (such as antioxidants, pharmacologically active compounds, neutraceuticals etc.) via photosynthesis, has been encapsulated within this core-shell system. Oximetry and fluorescence measurements highlight how this algal culture can remain photosynthetically active over an extraordinarily long period of 13 months for high value compound production, whilst entrapped within a highly porous, mechanically and chemically stable, optically transparent matrix, with no observable leaching of the cells from the core of the beads. HPLC has been employed to highlight the presence of excreted metabolites, based on neutral sugar building blocks such as arabinose, galactose and xylose, in the surrounding media. These results reveal how this kind of high performance, low-cost, and easily scaleable core-shell living material could be employed in large scale photobioreactors (PBRs), to potentially facilitate metabolite harvesting whilst protecting the culture from external contamination and for green energy production and environmental (CO 2 ) remediation.

Improvement of Biological Organisms Using Functional Material Shells

“…As a result, the silica immobilized thylakoids can stably produce oxygen for long period of time aiming as a “photo‐bioreactor”. Similar strategy is also applied on plant cells, cyanobacteria and chlorophyta . And the material shell encapsulated cells maintain their functions for dozens of weeks.…”

Encapsulation of Multiple Microalgal Cells via a Combination of Biomimetic Mineralization and LbL Coating

“…To that end, the immobilization of microbial cells, with its ease of cell separation and low contamination risk, is a widely employed method. Optically transparent silica beads and biocompatible natural polymers, such as alginate or agarose, have been shown to be effective for immobilized culture applications [ 7 , 45 , 46 , 47 ]. While calcium alginate, with its simple synthetic procedure [ 48 ], is the most commonly used natural polymer for the microencapsulation of cells, thermal stability and swelling are issues of concern.…”

Synthesis of alginate‐silica hybrid hydrogel for biocatalytic conversion by β‐glucosidase in microreactor

“…The formulation of alginate-silica hybrid monoliths was inspired by diffusion gelation based synthesis [35] but prepared based on internal gelation method ( Fig. 1).…”

“…These methods are based on silicacoated alginate hydrogels [14,34]. Combining alginate and silica as a hybrid gel provides advantages such as improved surface area and chemical and mechanical stability that prevent enzyme denaturation [15,35]. However, they lack suitable surface area, pore size, and more importantly homogenity, which causes diffusion problems and results in enzyme leakage [36,37].…”