MTMS-Based Aerogel Constructs for Immobilization of Plant Hairy Roots: Effects on Proliferation of Rindera graeca Biomass and Extracellular Secretion of Naphthoquinones

Effect of Silica Xerogel Functionalization on Intensification of Rindera graeca Transgenic Roots Proliferation and Boosting Naphthoquinone Production

Secondary metabolites derived from plants are recognized as valuable products with several successful applications in the pharmaceutical, cosmetic, and food industries. The major limitation to the broader implementation of these compounds is their low manufacturing efficiency. Current efforts to overcome unprofitability depend mainly on biotechnological methods, especially through the application of plant in vitro cultures. This concept allows unprecedented bioengineering opportunities for culture system modifications with in situ product removal. The silica-based xerogels can be used as a novel, porous biomaterial characterized by a large surface area and high affinity to lipophilic secondary metabolites produced by plant tissue. This study aimed to investigate the influence of xerogel-based biomaterials functionalized with methyl, hydroxyl, carboxylic, and amine groups on Rindera graeca transgenic root growth and the production of naphthoquinone derivatives. The application of xerogel-based scaffolds functionalized with the methyl group resulted in more than 1.5 times higher biomass proliferation than for reference untreated culture. The naphthoquinone derivatives' production was noted exclusively in culture systems supplemented with xerogel functionalized with methyl and hydroxyl groups. Applying chemically functionalized xerogels as in situ adsorbents allowed for the enhanced growth and productivity of in vitro cultured R. graeca transgenic roots, facilitating product isolation due to their selective and efficient accumulation.

Stress-Induced Intensification of Deoxyshikonin Production in Rindera graeca Hairy Root Cultures with Ester-Based Scaffolds

In vitro plant cell and tissue culture systems allow for controlling a wide range of culture environmental factors selectively influencing biomass growth and the yield of secondary metabolites. Among the most efficient methods, complex supplementation of the culture medium with elicitors, precursors, and other functional substances may significantly enhance valuable metabolite productivity through a stress induction mechanism. In the search for novel techniques in plant experimental biotechnology, the goal of the study was to evaluate stress-inducing properties of novel biodegradable ester-based scaffolds made of poly(glycerol sebacate) (PGS) and poly(lactic acid) (PLA) influencing on the growth and deoxyshikonin productivity of Rindera graeca hairy roots immobilized on the experimental constructs. Rindera graeca hairy roots were maintained under the dark condition for 28 days in three independent systems, i.e., (i) non-immobilized biomass (a reference system), (ii) biomass immobilized on PGS scaffolds, and (iii) biomass immobilized on PLA scaffolds. The stress-inducing properties of the applied polymerized esters selectively impacted R. graeca hairy roots. The PGS scaffolds caused the production of deoxyshikonin, which does not occur in other culture systems, and PLA promoted biomass proliferation by doubling its increase compared to the reference system.

Biotechnology and In Vitro Culture as an Alternative System for Secondary Metabolite Production

Medicinal plants are rich sources of bioactive compounds widely used as medicaments, food additives, perfumes, and agrochemicals. These secondary compounds are produced under stress conditions to carry out physiological tasks in plants. Secondary metabolites have a complex chemical structure with pharmacological properties. The widespread use of these metabolites in a lot of industrial sectors has raised the need to increase the production of secondary metabolites. Biotechnological methods of cell culture allow the conservation of plants, as well as the improvement of metabolite biosynthesis and the possibility to modify the synthesis pathways. The objective of this review is to outline the applications of different in vitro culture systems with previously reported relevant examples for the optimal production of plant-derived secondary metabolites.

Selective Impact of MTMS-Based Xerogel Morphology on Boosted Proliferation and Enhanced Naphthoquinone Production in Cultures of Rindera graeca Transgenic Roots

In situ extraction is a method for separating plant secondary metabolites from in vitro systems of plant biomass cultures. The study aimed to investigate the MTMS-based xerogels morphology effect on the growth kinetics and deoxyshikonin productivity in xerogel-supported in vitro culture systems of Rindera graeca hairy root. Cultures were supplemented with three types of xerogel, i.e., mesoporous gel, microporous gel, and agglomerated precipitate, in the disintegrated or monolithic form. Structure, oil sorption capacity, and SEM analyses for xerogel-based additives were performed. Application of monolithic macroporous xerogel resulted in the highest biomass proliferation, i.e., 5.11-fold fresh biomass increase after four weeks of the screening culture. The highest deoxyshikonin production (i.e., 105.03 µg) was noted when hairy roots were maintained with particles of disintegrated mesoporous xerogel. The detailed kinetics investigations (6-week culture) revealed the highest growth of hairy root biomass and secondary metabolite production, equaling 9.46-fold fresh weight biomass and 204.08 µg deoxyshikonin, respectively. MTMS-based xerogels have been recognized as selective biocompatible scaffolds for boosting the proliferation of transgenic roots or for productivity enhancement of naphthoquinones without detrimental effects on biomass growth, and their successful applicability in in situ removal of secondary plant metabolites has been experimentally confirmed.