Enhanced taxol production and release in Taxus chinensis cell suspension cultures with selected organic solvents and sucrose feeding

Biotechnological Approaches to Producing Natural Antioxidants: Anti-Ageing and Skin Longevity Prospects

Plants are the main source of bioactive compounds that can be used for the formulation of cosmetic products. Plant extracts have numerous proven health benefits, among which are anti-ageing and skin-care properties. However, with the increased demand for plant-derived cosmetic products, there is a crucial prerequisite for establishing alternative approaches to conventional methods to ensure sufficient biomass for sustainable production. Plant tissue culture techniques, such as in vitro root cultures, micropropagation, or callogenesis, offer the possibility to produce considerable amounts of bioactive compounds independent of external factors that may influence their production. This production can also be significantly increased with the implementation of other biotechnological approaches such as elicitation, metabolic engineering, precursor and/or nutrient feeding, immobilization, and permeabilization. This work aimed to evaluate the potential of biotechnological tools for producing bioactive compounds, with a focus on bioactive compounds with anti-ageing properties, which can be used for the development of green-label cosmeceutical products. In addition, some examples demonstrating the use of plant tissue culture techniques to produce high-value bioactive ingredients for cosmeceutical applications are also addressed, showing the importance of these tools and approaches for the sustainable production of plant-derived cosmetic products.

Comparison of elicitor-based effects on metabolic responses of Taxus × media hairy roots in perfluorodecalin-supported two-phase culture system

Two lines of Taxus × media hairy roots harbouring or not the TXS transgene demonstrated diverse gene expression and taxane yield during cultivation in PFD-supported two liquid-phase culture system. Two lines of Taxus × media hairy roots were subjected to single or twice-repeated supplementation with methyl jasmonate, sodium nitroprusside, L-phenylalanine, and sucrose feeding. One line harboured transgene of taxadiene synthase (ATMA), while the second (KT) did not. Both hairy root lines were cultured in two-phase culture systems containing perfluorodecalin (PFD) in aerated or degassed form. The relationship between TXS (taxadiene synthase), BAPT (baccatin III: 3-amino, 3-phenylpropanoyltransferase), and DBTNBT (3'-N-debenzoyl-2-deoxytaxol-N-benzoyltransferase) genes and taxane production was analysed. The ATMA and KT lines differed in their potential for taxane accumulation, secretion, and taxane profile. In ATMA biomass, both paclitaxel and baccatin III were detected, while in KT roots only paclitaxel. The most suitable conditions for taxane production for ATMA roots were found in single-elicited supported with PFD-degassed cultures (2 473.29 ± 263.85 µg/g DW), whereas in KT roots in single-elicited cultures with PFD-aerated (470.08 ± 25.15 µg/g DW). The extracellular levels of paclitaxel never exceeded 10% for ATMA roots, while for KT increased up to 76%. The gene expression profile was determined in single-elicited cultures supported with PFD-degassed, where in ATMA roots, the highest taxane yield was obtained, while in KT the lowest one. The gene expression pattern in both investigated root lines differed substantially what resulted in taxane yield characterized particular lines. The highest co-expression of TXS, BAPT and DBTNBT genes noted for ATMA roots harvested 48 h after elicitation corresponded with their higher ability for taxane production in comparison with the effects observed for KT roots.

Endophytic Fungi-Alternative Sources of Cytotoxic Compounds: A Review

Cancer is a major cause of death worldwide, with an increasing number of cases being reported annually. The elevated rate of mortality necessitates a global challenge to explore newer sources of anticancer drugs. Recent advancements in cancer treatment involve the discovery and development of new and improved chemotherapeutics derived from natural or synthetic sources. Natural sources offer the potential of finding new structural classes with unique bioactivities for cancer therapy. Endophytic fungi represent a rich source of bioactive metabolites that can be manipulated to produce desirable novel analogs for chemotherapy. This review offers a current and integrative account of clinically used anticancer drugs such as taxol, podophyllotoxin, camptothecin, and vinca alkaloids in terms of their mechanism of action, isolation from endophytic fungi and their characterization, yield obtained, and fungal strain improvement strategies. It also covers recent literature on endophytic fungal metabolites from terrestrial, mangrove, and marine sources as potential anticancer agents and emphasizes the findings for cytotoxic bioactive compounds tested against specific cancer cell lines.

Plant cell culture strategies for the production of natural products

Plants have evolved a vast chemical cornucopia to support their sessile lifestyles. Man has exploited this natural resource since Neolithic times and currently plant-derived chemicals are exploited for a myriad of applications. However, plant sources of most high-value natural products (NPs) are not domesticated and therefore their production cannot be undertaken on an agricultural scale. Further, these plant species are often slow growing, their populations limiting, the concentration of the target molecule highly variable and routinely present at extremely low concentrations. Plant cell and organ culture constitutes a sustainable, controllable and environmentally friendly tool for the industrial production of plant NPs. Further, advances in cell line selection, biotransformation, product secretion, cell permeabilisation, extraction and scale-up, among others, are driving increases in plant NP yields. However, there remain significant obstacles to the commercial synthesis of high-value chemicals from these sources. The relatively recent isolation, culturing and characterisation of cambial meristematic cells (CMCs), provides an emerging platform to circumvent many of these potential difficulties. [BMB Reports 2016; 49(3): 149-158]

Sucrose-enhanced biosynthesis of medicinally important antioxidant secondary metabolites in cell suspension cultures of Artemisia absinthium L

Natural products are gaining tremendous importance in pharmaceutical industry and attention has been focused on the applications of in vitro technologies to enhance yield and productivity of such products. In this study, we investigated the accumulation of biomass and antioxidant secondary metabolites in response to different carbohydrate sources (sucrose, maltose, fructose and glucose) and sucrose concentrations (1, 3, 5, 7 and 9 %). Moreover, the effects of 3 % repeated sucrose feeding (day-12, -18 and -24) were also investigated. The results showed the superiority of disaccharides over monosaccharides for maximum biomass and secondary metabolites accumulation. Comparable profiles for maximum biomass were observed in response to sucrose and maltose and initial sucrose concentrations of 3 and 5 %. Maximum total phenolic and total flavonoid contents were displayed by cultures treated with sucrose and maltose; however, initial sucrose concentrations of 5 and 7 % were optimum for both classes of metabolites, respectively. Following 3 % extra sucrose feeding, cultures fed on day-24 (late-log phase) showed higher biomass, total phenolic and total flavonoid contents as compared to control cultures. Highest antioxidant activity was exhibited by maltose-treated cultures. Moreover, sucrose-treated cultures displayed positive correlation of antioxidant activity with total phenolics and total flavonoids production. This work describes the stimulatory role of disaccharides and sucrose feeding strategy for higher accumulation of phenolics and flavonoids, which could be potentially scaled up to bioreactor level for the bulk production of these metabolites in suspension cultures of A. absinthium.

Enhancement of Palmarumycin C12 and C13 Production by the Endophytic Fungus Berkleasmium sp. Dzf12 in an Aqueous-Organic Solvent System

The endophytic fungus Berkleasmium sp. Dzf12, isolated from Dioscorea zingiberensis, was found to produce palmarumycins C₁₂ and C₁₃ which possess a great variety of biological activities. Seven biocompatible water-immiscible organic solvents including n-dodecane, n-hexadecane, 1-hexadecene, liquid paraffin, dibutyl phthalate, butyl oleate and oleic acid were evaluated to improve palmarumycins C₁₂ and C₁₃ production in suspension culture of Berkleasmium sp. Dzf12. Among the chosen solvents both butyl oleate and liquid paraffin were the most effective to improve palmarumycins C₁₂ and C₁₃ production. The addition of dibutyl phthalate, butyl oleate and oleic acid to the cultures of Berkleasmium sp. Dzf12 significantly enhanced palmarumycin C₁₂ production by adsorbing palmarumycin C₁₂ into the organic phase. When butyl oleate was fed at 5% (v/v) in medium at the beginning of fermentation (day 0), the highest palmarumycin C₁₂ yield (191.6 mg/L) was achieved, about a 34.87-fold increase in comparison with the control (5.3 mg/L). n-Dodecane, 1-hexadecene and liquid paraffin had a great influence on the production of palmarumycin C₁₃. When liquid paraffin was added at 10% (v/v) in medium on day 3 of fermentation, the palmarumycin C₁₃ yield reached a maximum value (134.1 mg/L), which was 4.35-fold that of the control (30.8 mg/L). Application of the aqueous-organic solvent system should be a simple and efficient process strategy for enhancing palmarumycin C₁₂ and C₁₃ production in liquid cultures of the endophytic fungus Berkleasmium sp. Dzf12.

Cambial meristematic cells: a platform for the production of plant natural products

Plant cell culture constitutes a sustainable, controllable and environmentally friendly tool to produce natural products for the pharmaceutical, cosmetic and industrial biotechnology industries. However, there are significant obstacles to the commercial synthesis of high value chemicals from plant culture including low yields, performance instability, slow plant cell growth, industrial scale-up and downstream processing. Cambial meristematic cells constitute a platform to ameliorate many of these potential problems enabling the commercial production of high value chemicals.

Plant natural products: history, limitations and the potential of cambial meristematic cells

Humans have utilised plant derived natural products as medicines for millenia. Moreover, many contemporary pharmaceuticals are also natural products or derivatives thereof. However, the full potential of these compounds remains to be exploited because often they are: complex and difficult to synthesise; found in low quantities; produced by undomesticated and sometimes rare plants; and, their synthesis is routinely influenced by weather conditions. Potentially, the in vitro culture of cells from the corresponding plant species could circumvent some of these problems but the growth of plant cells on an industrial scale is also problematic. The recent isolation and culture of cambial meristematic cells (CMCs), stem cells which ordinarily generate the plant vasculature, may now provide a key platform technology to help realise the full potential of plant natural products.

Recent advances towards development and commercialization of plant cell culture processes for the synthesis of biomolecules

Plant cell culture systems were initially explored for use in commercial synthesis of several high-value secondary metabolites, allowing for sustainable production that was not limited by the low yields associated with natural harvest or the high cost associated with complex chemical synthesis. Although there have been some commercial successes, most notably paclitaxel production from Taxus sp., process limitations exist with regards to low product yields and inherent production variability. A variety of strategies are being developed to overcome these limitations including elicitation, in situ product removal and metabolic engineering with single genes and transcription factors. Recently, the plant cell culture production platform has been extended to pharmaceutically active heterologous proteins. Plant systems are beneficial because they are able to produce complex proteins that are properly glycosylated, folded and assembled without the risk of contamination by toxins that are associated with mammalian or microbial production systems. Additionally, plant cell culture isolates transgenic material from the environment, allows for more controllable conditions over field-grown crops and promotes secretion of proteins to the medium, reducing downstream purification costs. Despite these benefits, the increase in cost of heterologous protein synthesis in plant cell culture as opposed to field-grown crops is significant and therefore processes must be optimized with regard to maximizing secretion and enhancing protein stability in the cell culture media. This review discusses recent advancements in plant cell culture processing technology, focusing on progress towards overcoming the problems associated with commercialization of these production systems and highlighting recent commercial successes.

Paclitaxel uptake and transport in Taxus cell suspension cultures

The transport of paclitaxel in Taxus canadensis suspension cultures was studied with a fluorescence analogue of paclitaxel (Flutax-2(®)) in combination with flow cytometry detection. Experiments were carried out using both isolated protoplasts and aggregated suspension cell cultures. Flutax-2(®) was shown to be greater than 90% stable in Taxus suspension cultures over the required incubation time (24 hours). Unlabeled paclitaxel was shown to inhibit the cellular uptake of Flutax-2(®), although structurally similar taxanes such as cephalomannine, baccatin III, and 10-deacetylbaccatin III did not inhibit Flutax-2(®) uptake. Saturation kinetics of Flutax-2(®) uptake was demonstrated. These results indicate the presence of a specific transport system for paclitaxel. Suspension cells elicited with methyl jasmonate accumulated 60% more Flutax-2(®) than unelicited cells, possibly due to an increased cellular storage capacity following methyl jasmonate elicitation. The presence of a specific mechanism for paclitaxel transport is an important first result that will provide the basis of more detailed studies as well as the development of targeted strategies for increased paclitaxel secretion to the extracellular medium.

Analysis of aggregate size as a process variable affecting paclitaxel accumulation in Taxus suspension cultures

Plant cell aggregates have long been implicated in affecting cellular metabolism in suspension culture, yet the rigorous characterization of aggregate size as a process variable and its effect on bioprocess performance has not been demonstrated. Aggregate fractionation and analysis of biomass-associated product is commonly used to assess the effect of aggregation, but we establish that this method is flawed under certain conditions and does not necessarily agree with comprehensive studies of total culture performance. Leveraging recent advances to routinely measure aggregate size distributions, we developed a simple method to manipulate aggregate size and evaluate its effect on the culture as a whole, and found that Taxus suspension cultures with smaller aggregates produced significantly more paclitaxel than cultures with larger aggregates in two cell lines over a range of aggregate sizes, and where biomass accumulation was equivalent before elicitation with methyl jasmonate. Taxus cuspidata (T. cuspidata) P93AF cultures with mean aggregate sizes of 690 and 1,100 μm produced 22 and 11 mg/L paclitaxel, respectively, a twofold increase for smaller aggregates, and T. cuspidata P991 cultures with mean aggregate sizes of 400 and 840 μm produced 6 and 0.3 mg/L paclitaxel, respectively, an increase of 20-fold for smaller aggregates. These results demonstrate the importance of validating experiments aimed at a specific phenomenon with total process studies, and provide a basis for treating aggregate size as a targeted process variable for rational control strategies.

Effect of Antioxidants and Carbohydrates in Callus Cultures of Taxus brevifolia: Evaluation of Browning, Callus Growth, Total Phenolics and Paclitaxel Production

INTRODUCTION

To control the tissue browning phenomenon, callus growth, total phenolics and paclitaxel production, in the current investigation, we evaluated the effects of citric acid and ascorbic acid (as antioxidants) and glucose, fructose and sucrose in callus cultures of Taxus brevifolia.

METHODS

To obtain healthy callus/cell lines of Taxus brevifolia, the effects of two antioxidants ascorbic acid (100-1000 mg/L) and citric acid (50-500 mg/L), and three carbohydrates (glucose, fructose and sucrose (5-10 g/L)) were studied evaluating activities of polyphenol oxidase (PPO) and peroxidase (PO) enzymes, callus growth/browning, total phenolics and paclitaxel production.

RESULTS

These antioxidants (ascorbic acid and citric acid) failed to show significant effects on callus growth, browning intensity or paclitaxel production. However, the carbohydrates imposed significant effects on the parameters studied. High concentrations of both glucose and sucrose increased the browning intensity, thus decreased callus growth. Glucose increased paclitaxel production, but sucrose decreased it.

CONCLUSION

These results revealed that the browning phenomenon can be controlled through supplementation of the growth media with glucose, sucrose (5 g/L) and fructose (10 g/L), while increased paclitaxel production can be obtain by the optimized media supplemented with glucose (10 g/L), sucrose and fructose (5 g/L).

Metabolic responses of Taxus media transformed cell cultures to the addition of methyl jasmonate

Dedifferentiated Taxus media cell cultures presenting the same genetic characteristics as the parent culture were established from transformed roots. Two transformed cell lines were studied: Rol C, carrying the T-DNA of A. rhizogenes 9,402 and TXS, carrying both the T-DNA of A. rhizogenes and the txs transgene of T. baccata under the control of the 35S CaMV promoter. In the second part of a previously optimized two-stage system, the transformed cell lines were cultured in a production medium supplemented with the elicitor methyl jasmonate. Taxane production in the transformed cultures was compared with an untransformed T. media cell line cultured in the same conditions. The highest taxane production was observed in the TXS cell line when cultured in the optimized production medium with methyl jasmonate, being 265% greater than in the untransformed control and 170% greater than in the Rol C cell line. However, txs expression and the activity of the enzyme taxadiene synthase in the TXS cells were lower than in the line carrying only the rol genes (Rol C). It is also noteworthy that the taxane production as well as the txs gene expression and TXS activity in all the cell lines, both transformed and untransformed, were clearly dependent on the elicitor action.

Cultured cambial meristematic cells as a source of plant natural products

A plethora of important, chemically diverse natural products are derived from plants. In principle, plant cell culture offers an attractive option for producing many of these compounds. However, it is often not commercially viable because of difficulties associated with culturing dedifferentiated plant cells (DDCs) on an industrial scale. To bypass the dedifferentiation step, we isolated and cultured innately undifferentiated cambial meristematic cells (CMCs). Using a combination of deep sequencing technologies, we identified marker genes and transcriptional programs consistent with a stem cell identity. This notion was further supported by the morphology of CMCs, their hypersensitivity to γ-irradiation and radiomimetic drugs and their ability to differentiate at high frequency. Suspension culture of CMCs derived from Taxus cuspidata, the source of the key anticancer drug, paclitaxel (Taxol), circumvented obstacles routinely associated with the commercial growth of DDCs. These cells may provide a cost-effective and environmentally friendly platform for sustainable production of a variety of important plant natural products.

Studied enhancement strategies for phytoestrogens production in shake flasks by suspension culture of Psoralea corylifolia

This study proposed secondary metabolites incremental yield due to manipulation of nutrient components into the culture medium. To validate this, the effects of nutrients such as carbon, phosphate and nitrogen on growth and production of phytoestrogens daidzein and genistein by suspension cultures of Psoralea corylifolia was investigated for the first time. The maximum production of daidzein and genistein was achieved when sucrose and maltose used as a sole source of carbon. Suspension cell cultures enriched with sucrose (3%) stimulated accumulation of isoflavones daidzein (1.76% dry wt) and genistein (0.25% dry wt) compared to glucose, fructose and maltose. Sucrose feeding strategy significantly stimulated biomass growth and isoflavones (2.79% dry wt of daidzein and 0.32% dry wt of genistein) production rate. Reduced concentrations of phosphate (0.625 mM) promoted daidzein (1.89% dry wt) and genistein (0.26% dry wt) production by suspension cell cultures, whereas high amount (5mM) in medium was inhibited isoflavones production. It was observed that medium fortified with NH(4)(+) and NO(3)(-) alone inhibited production of isoflavones. The maximum production obtained of daidzein (2.20% dry wt) and genistein (0.29% dry wt) when medium comprised with NH(4)(+)/NO(3)(-) at ratio 20:40 mM as a nitrogen source. Similar nutrient components ratio when altered NH(4)(+)/NO(3)(-); 40:20mM) resulted in approximately 3-fold decrease in production. HPLC analysis revealed that suspension cells cultures leached out trace amount of daidzein and genistein into the culture medium.

Paclitaxel: a review of adverse toxicities and novel delivery strategies

Better known as Taxol (Bristol-Myers Squibb), paclitaxel is the first member of the taxane family to be used in cancer chemotherapy. The taxanes exert their cytotoxic effect by arresting mitosis through microtubule stabilization, resulting in cellular apoptosis. The use of paclitaxel as a chemotherapeutic agent has become a broadly accepted option in the treatment of patients with ovarian, breast and non-small cell lung cancers, malignant brain tumors, and a variety of other solid tumors. However, significant toxicities, such as myelosuppression and peripheral neuropathy, limit the effectiveness of paclitaxel-based treatment regimens. This review addresses the toxicities associated with paclitaxel treatment and describes existing and future strategies of paclitaxel administration directed at limiting these toxicities.

The dynamic variation of several important taxane content in post-harvest Taxus chinensis clippings

The dynamic variations of several important taxanes, taxol, baccatin III (B-III), 1-acety-5,7,10-deacetyl-baccatin I (DAB-I) and baccatin VI (B-VI), were investigated in post-harvest clippings of Taxus chinensis. The clippings were preserved over 20 days at two different temperatures (4 degrees C and room temperature), or by cuttage in the light and in the dark, or promptly dried. The accumulation of taxol in needles of the clippings was found increase in the initial stages of the stored period and then decreased gradually. The maximum accumulation of taxol occurred in the case of cold storing (4 degrees C) at day 3, doubling the data on the day when the biomass was harvested. In contrast, in the cases of cold storage and cuttage the contents of the other three taxanes showed a sharp decrease at the beginning and then an increase from 3 to 6 days, and subsequently a drop until day 20. The similar variation of taxane contents was not found in the needles of immediately dried clippings as well as in the stem samples of clippings. These results indicated that the content variation of taxol and related taxanes of post-harvest clippings was related to the manner of preservation, timing and plant tissue. Moreover, the mechanism of the fluctuation of the taxane contents in post-harvest clippings is discussed, in particular taxol biosynthesis in response to mechanical wounding of harvest.

Plant cell culture for production of paclitaxel and other taxanes

Great advances in cell cultures of Taxus spp. for production of Taxol (generic name: paclitaxel) and other taxanes (taxoids) have been achieved in the past decade. This article reviews the manipulation of inducing factors--elicitors, gas composition, osmotic pressure, and conditioned medium; bioprocessing strategies--combining of inducing techniques, two-phase and two-stage cultivation, semi-continuous and perfusion cultures, and feeding of precursors or sugars; and bioreactors and scale-up. Perspectives on a more rational and efficient process involving metabolic engineering are also discussed.

In situ extraction strategy affects benzophenanthridine alkaloid production fluxes in suspension cultures of Eschscholtzia californica

The effect of contact between cells and extractive phase on secondary metabolite production was investigated in two-phase suspension cultures of Eschscholtzia californica. A system was designed to extract benzophenanthridine alkaloids from the cell culture, without contact between XAD-7 resins and the cells: only medium was recirculated through a column packed with the extractive phase. This strategy was compared to the classic method of addition of resins directly into the cell suspension. Removal of the product directly from the medium enabled important increases in production of alkaloids, namely a 20-fold increase in sanguinarine production and a 10-fold increase in chelerythrine, with high recovery in the resin. The recirculation strategy greatly simplified the production process since the resins are easily recovered from the cell culture and enable harvest of product without termination of culture. However, due to limited flow rate, the recirculation strategy was slightly less effective than direct addition of resins into the cell suspension. In addition to enabling increased production, removal of secondary metabolites from the medium changed metabolic flux distribution, testifying to a complex control mechanism of production.

Enhanced production of plumbagin in immobilized cells of Plumbago rosea by elicitation and in situ adsorption

Cell cultures of Plumbago rosea were immobilized in calcium alginate and cultured in Murashige and Skoog's basal medium containing 10 mM CaCl(2) for the production of plumbagin, an important medicinal compound. Studies were carried to find out the impact of immobilization on the increased accumulation of this secondary metabolite. Immobilization in calcium alginate enhanced the production of plumbagin by three, two and one folds compared to that of control, un-crosslinked alginate and CaCl(2) treated cells respectively. Cell loading at a level of 20% to the polymer volume (Na-alginate) was optimal and maximum plumbagin was obtained. At higher cell loading (40-50%), lower plumbagin accumulation was noticed. Addition of 200 mg l(-1) chitosan as an elicitor to the immobilized cells resulted in eight and two folds higher accumulation of plumbagin over control and immobilized cells. Also, more than 70% of the plumbagin was released into the medium, which is highly desirable for easy recovery of the product. Sucrose utilization rate of the cells was higher when cells were subjected to in situ product removal using Amberlite XAD-7. This may indicate that the toxicity of plumbagin was reduced on cells when it was removed from the medium. Cells subjected to combined treatments of chitosan, immobilization and in situ extraction showed a synergistic effect and yielded 92.13 mg g(-1) DCW of plumbagin which is 21, 5.7, 2.5 times higher than control, immobilized, immobilized and elicited cells respectively.

Enhancement of shikonin production in single- and two-phase suspension cultures of Lithospermum erythrorhizon cells using low-energy ultrasound

This work demonstrates the use of low-energy ultrasound (US) to enhance secondary metabolite production in plant cell cultures. Suspension culture of Lithospermum erythrorhizon cells was exposed to low-power US (power density < or = 113.9 mW/cm(3)) for short periods (1-8 min). The US exposure significantly stimulated the shikonin biosynthesis of the cells, and at certain US doses, increased the volumetric shikonin yield by about 60%-70%. Meanwhile, the shikonin excreted from the cells was increased from 20% to 65%-70%, due partially to an increase in the cell membrane permeability by sonication. With combined use of US treatment and in situ product extraction by an organic solvent, or the two-phase culture, the volumetric shikonin yield was increased more than two- to threefold. Increasing in the number of US exposures during the culture process usually resulted in negative effects on shikonin yield but slight stimulation of shikonin excretion. US at relatively high energy levels caused slight cell growth depression (maximum 9% decrease in dry cell weight). Two key enzymes for the secondary metabolite biosynthesis of cells, phenylalanine ammonia lyase and p-hydroxybenzoic acid geranyltransferase, were found to be stimulated by the US. The US stimulation of secondary metabolite biosynthesis was attributed to the metabolic activity of cells activated by US, and more specifically, the defense responses of plant cells to the mechanical stress of US irradiation.

Biochemical engineering of the production of plant-specific secondary metabolites by cell suspension cultures

Plant cell culture has recently received much attention as a useful technology for the production of valuable plant-derived secondary metabolites such as paclitaxel and ginseng saponin. The numerous problems that yet bewilder the optimization and scale-up of this process have not been over emphasized. In spite of the great progress recorded in recent years towards the selection, design and optimization of bioreactor hardware, manipulation of environmental factors such as medium components, light irradiation, shear stress and O2 supply needs detailed investigations for each case. Recent advances in plant cell processes, including high-density suspension cultivation, continuous culture, process monitoring, modeling and control and scale-up, are also reviewed in this chapter. Further developments in bioreactor cultivation processes and in metabolic engineering of plant cells for metabolite production are expected in the near future.