Green bioprinting: Viability and growth analysis of microalgae immobilized in 3D‐plotted hydrogels versus suspension cultures

Abstract

Biotechnological processes using photosynthetic microorganisms are of growing industrial interest for the production of renewable energies, platform chemicals or pharmaceutical drugs. Microalgae can be cultivated in suspension, or immobilized by active or passive approaches. We analyzed microalgae growth and population dynamics at different temperatures and illumination conditions in suspension and immobilized in 3D-plotted hydrogels. For microbial processes, the viability of the organisms is essential as productivity depends directly on the number of active catalytic units. Therefore it is important to understand how cultivation conditions influence the population viability. We found that even under non-optimal temperatures, the number of viable microalgae was directly influenced by length of exposure to light for both suspension and immobilized cultures. The cultivation of microalgae in 3D-plotted hydrogels, a highly organized immobilization technique, affords new fields of applications, e.g. the co-cultivation of different microorganisms in close vicinity but without direct contact.www.els-journal.com Page 3 Engineering in Life SciencesThis article is protected by copyright. All rights reserved. AbstractIn this study, microalgae were cultivated in the form of suspension cultures using a new structurally organized immobilization technique called "Green Bioprinting". This technique allows the co-cultivation of different microorganisms in close vicinity to, but without direct contact with microalgae. The goal is to improve the oxygen supply of different cell types by photosynthetic oxygen evolution. However, more information on the optimum culture conditions for different microalgae is necessary. Therefore, Chlamydomonas reinhardtii 11.32b and Chlorella sorokiniana UTEX1230 were suspended in culture medium or embedded in hydrogels by the 3D-bioprinting process followed by cultivation under different temperatures (26 °C, 30 °C or 37 °C) and modes of illumination (continuous illumination or a 14/10 hours light/dark cycle). Concluding, the 3D-bioprinting immobilization represents a technique to cultivate microalgae at a high viability and growth rate even under non-optimal temperature conditions.

Methylcellulose – a versatile printing material that enables biofabrication of tissue equivalents with high shape fidelity

“…32 Apart from bioprinting of mammalian cells, it was previously shown that the blend of alginate and mc forms a bioink which is suitable for Green Bioprinting of micro algae. [48][49][50] The micro algae could be bioprinted alone and in coculture with mammalian cells in alginate-mc. 48 Crucially, the microalgae did not lose their photosynthetic activity after fabrication and thus might be able to provide oxygen needed by the surrounding mammalian cells.…”

Therapeutic Applications of Phytoplankton, with an Emphasis on Diatoms and Coccolithophores

“…In vitro Therapeutic drugs [151] Green microalgae Chlamydomonas reinhardtii Co-culture with mammalian cells…”

“…[150] By using 3D bioprinting of cells into scaffolds, C. reinhardtii and C. sorokiniana microalgae were imbedded in a highly structural organization alginate-based hydrogel scaffold. [151] 3D bioprinting has emerged as a viable technique to design and create scaffolds embedded with cells for tissue and organ growth with clinically relevant size, shape, and structural integrity. [152] This involves a computer-controlled 3D printer able to transform a computer aided design into rapid and high-precision construction of 3D biological structures using an appropriate bioink (Figure 17A).…”

“…[153] Bioprinted microalgae into alginate-based hydrogels were subjected to various cultivation temperatures and modes of illumination and compared with the same microalgae suspension cultures under similar conditions. [151] During the photoautotrophic cultivation, the physiological state (i.e., viability) of microalgae populations was monitored using single-cell flow cytometry analysis (microalgae suspension cultures) and, based on chlorophyll autofluorescence and fluorescent-dye-based membrane staining, fluorescence image analysis (microalgae imbedded in hydrogel). Data analysis revealed that viability of C. reinhardtii microalgae increased approximately 30% when immobilized in the alginate microgel, irrespective of the temperature and illumination conditions.…”

“…B,C) Reproduced and modified with permission. [151] Copyright 2015, John Wiley & Sons. D-H) Reproduced and modified with permission.…”