Rate Of Sucrose Hydrolysis Research Articles

Yeast β‒fructosidase-catalyzed synthesis of tyrosol fructoside in mono- and biphasic organic–aqueous systems

Abstract Tyrosol and its glycosides offer cell protection from oxidative stress and various health benefits. In this study, Saccharomyces cerevisiae β‒fructosidase potential for synthesizing tyrosol fructoside in mono- and biphasic solvent systems was assessed using 1.5 M sucrose, 10 g/L or 25 g/L tyrosol, at pH 6 and 40°C. Monophasic organic–water systems were designed with nine organic solvents (log P ranging from -1.35 to 0.5). Initial rates of sucrose hydrolysis, tyrosol and sucrose transfructosylation and tyrosol fructoside yields were evaluated. The hydrolytic activity increased with the addition of 5–15% organic solvents, revealing no clear correlation between the log P and sucrose hydrolysis rate. Simultaneously, transfructosylation reaction rates decreased, despite lower water activity. Notably, the effect of log P on tyrosol transfructosylation was observed in 70:30 (v/v) aqueous/organic biphasic systems. Differences in tyrosol fructoside synthesis in six biphasic reaction media were attributed to the unequal solubility of tyrosol in the organic phase, impacting its availability for the enzyme. Product yields were either similar to or lower than those in aqueous media, with no tyrosol fructoside partitioning into the organic phase, thus no effect of product stripping could be observed. Consequently, transfructosylation of tyrosol proves most effective in organic solvent-free media.

Catalytic action of alternansucrase on sucrose under in vitro simulated gastric conditions

Alternansucrase, a glucosyltransferase, is currently used to produce slowly digestible alternan oligosaccharides or maltooligosaccharides from sucrose. These oligosaccharides are popular for food fortification to lower postprandial glucose levels. This study aimed to explore the enzymatic reaction of alternansucrase in simulated in vitro gastric reaction conditions. Under the studied conditions, SucroSEB (a model enzyme for alternansucrase) hydrolyzed the sucrose and transglycosylated the glucose to produce glucans, both in the absence and presence of acceptors. The preference of the acceptor was maltose˃ raffinose˃ lactose. The rate of sucrose hydrolysis was significantly higher in the presence of maltose (p = 0.024). The glucans formed during the reaction included oligomers (DP 3–10) and polymers (DP ≥ 11), both of which increased over time. These glucans contained α-1,3 and α-1,6 glycosidic linkages, confirmed by 1H and 13C NMR. They were slowly and partially digestible in the presence of rat intestinal extract in contrast to the complete and rapid digestion of starch. The glucans formed after a longer gastric reaction time exhibited higher dietary fiber potential (19.145 ± 4.77 %; 60 min) compared to those formed during the initial phase (2.765 ± 0.19 %; 15 min). Overall, this study demonstrated the efficacy of SucroSEB in converting sucrose to slowly and partially digestible glucans under simulated in vitro gastric conditions.

One pot two-alkali clarification process to minimize sucrose degradation of clarified sugarcane juice during evaporation

Chemical degradation of sucrose during evaporation is a key production issue for the sugar cane industry. Although targeting higher juice pH using Lime Saccharate (LS) is commonly recommended to reduce sucrose degradation, this study showed reduced sucrose degradation occurs with increasing juice pH at the expense of higher invert sugar degradation and residual Ca2+ which could respectively lead to increase in juice colour and higher scaling propensity. The study also showed that Na+ and K+ ions have minimal effect on sucrose hydrolysis, while Ca2+ and Mg2+ increased the rate of sucrose hydrolysis through reducing juice pH and via complexation with the sucrose molecule. With this knowledge, a novel two-stage clarification method using a hybrid alkaline agent compared to LS was assessed for sucrose degradation and clarification performance. The results showed that LS/Mg(OH)2, LS/Na2CO3, LS/KOH and LS/NaOH showed lower sucrose degradation than the conventional LS method with up to 53% lower residual Ca2+ levels. LS/KOH and LS/NaOH achieved clarification performances comparable to the LS under the tested conditions while, LS/Mg(OH)2 and LS/Na2CO3 would further require further testing to improve clarification performance.

Integration of food raw materials, food microbiology, and food additives: systematic research and comprehensive insights into sweet sorghum juice, Clostridium tyrobutyricum TGL-A236 and bio-butyric acid.

Sweet sorghum juice is a typical production feedstock for natural, eco-friendly sweeteners and beverages. Clostridium tyrobutyricum is one of the widely used microorganisms in the food industry, and its principal product, bio-butyric acid is an important food additive. There are no published reports of Clostridium tyrobutyricum producing butyric acid using SSJ as the sole substrate without adding exogenous substances, which could reach a food-additive grade. This study focuses on tailoring a cost-effective, safe, and sustainable process and strategy for their production and application. This study modeled the enzymolysis of non-reducing sugars via the first/second-order kinetics and added food-grade diatomite to the hydrolysate. Qualitative and quantitative analysis were performed using high-performance liquid chromatography, gas chromatography-mass spectrometer, full-scale laser diffraction method, ultra-performance liquid chromatography-tandem mass spectrometry, the cell double-staining assay, transmission electron microscopy, and Oxford nanopore technology sequencing. Quantitative real-time polymerase chain reaction, pathway and process enrichment analysis, and homology modeling were conducted for mutant genes. The treated sweet sorghum juice showed promising results, containing 70.60 g/L glucose and 63.09 g/L fructose, with a sucrose hydrolysis rate of 98.29% and a minimal sucrose loss rate of 0.87%. Furthermore, 99.62% of the colloidal particles and 82.13% of the starch particles were removed, and the concentrations of hazardous substances were effectively reduced. A food microorganism Clostridium tyrobutyricum TGL-A236 with deep utilization value was developed, which showed superior performance by converting 30.65% glucose and 37.22% fructose to 24.1364 g/L bio-butyric acid in a treated sweet sorghum juice (1:1 dilution) fermentation broth. This titer was 2.12 times higher than that of the original strain, with a butyric acid selectivity of 86.36%. Finally, the Genome atlas view, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and evolutionary genealogy of genes: Non-supervised Orthologous (eggNOG) functional annotations, three-dimensional structure and protein cavity prediction of five non-synonymous variant genes were obtained. This study not only includes a systematic process flow and in-depth elucidation of relevant mechanisms but also provides a new strategy for green processing of food raw materials, improving food microbial performance, and ensuring the safe production of food additives.

Ultrasensitive and real-time detection of chemical reaction rate based on the photonic spin Hall effect

A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. However, the precise and real-time detection of the reaction rate remains challenging due to its fast and dynamical process. In this paper, the photonic spin Hall effect is proposed to realize the ultrasensitive and real-time detection of the reaction rate of sucrose hydrolysis. By incorporating with quantum weak measurement, the photonic spin-Hall shift acts as the measurement pointer, and the optical rotation in the process of sucrose hydrolysis acts as the postselection state. The high measurement resolution with 1.25 × 10−4 degree is achieved due to the weak-value amplification in quantum weak measurement which outperforms the standard polarimeter. In our scheme, the amplified measurement pointer is real-time monitoring the chemical reaction process. It does not involve any mechanical adjustment of optical elements once the experimental setup is established and thereby realizes a real-time detection of the dynamic chemical reaction.

Optimization of whole-cell biotransformation for scale-up production of \u03b1-arbutin from hydroquinone by the use of recombinant Escherichia coli

α-Arbutin is an effective skin-whitening cosmetic ingredient and hyperpigmentation therapy agent. It can be synthesized by one-step enzymatic glycosylation of hydroquinone (HQ), but limited by the low yield. Amylosucrase (Amy-1) from Xanthomonas campestris pv. campestris 8004 was recently identified with high HQ glycosylation activity. In this study, whole-cell transformation by Amy-1 was optimized and process scale-up was evaluated in 5000-L reactor. In comparison with purified Amy-1, whole-cell catalyst of recombinant E. coli displays better tolerance against inhibitors (oxidized products of HQ) and requires lower molar ratio of sucrose and HQ to reach high conversion rate (> 99%). Excess accumulation of glucose (0.6–1.0 M) derived from sucrose hydrolysis inhibits HQ glycosylation rate by 46–60%, which suggests the importance of balancing HQ glycosylation rate and sucrose hydrolysis rate by adjusting the activity of whole-cell catalyst and HQ-fed rate. Using optimal conditions, 540 mM of final concentration and 95% of molar conversion rate were obtained within 13–18 h in laboratory scale. For industrial scale-up production, 398 mM and 375 mM of final concentration with high conversion rates (~ 95%) were obtained in 3500-L and 4000-L of reaction volume, respectively. These yields and productivities (4.5–4.9 kg kL−1 h−1) were the highest by comparing to the best we known. Hence, high-yield production of α-arbutin by batch-feeding whole-cell biotransformation was successfully achieved in the 5000-L reaction scale.

Ultrasound assisted enzymatic hydrolysis of sucrose catalyzed by invertase: Investigation on substrate, enzyme and kinetics parameters

This work studied the ultrasound technology as an alternative to enhance the reaction of sucrose inversion. To achieve it, the effect of ultrasound processing was evaluated in three situations: the reaction (invertase acting on substrate under ultrasound processing), the isolated substrate (sucrose) and the isolated enzyme (invertase). Ultrasound (25 kHz, 22 W/L) processing was conducted under different conditions of pH and temperature. The ultrasound assisted reaction was accelerated in relation to the conventional processing. This process increased the sucrose hydrolysis rate up to 33% at 40 °C, and 30% at 30 °C. The ultrasound as a pre-treatment method did not promote sucrose hydrolysis, but slightly reduced the invertase activity, independently of the pH and temperature of evaluation. Sonication also increased Vmax (increased of 23%) and maintained constant Km, indicating that the ultrasound accelerated mass transfer during the reaction, but did not directly affected the enzyme. In addition, the invertase catalytic efficiency enhanced 27% under sonication. Therefore, ultrasound technology emerges as an interesting alternative to improve the invertase performance, accelerating enzymatic reaction.

Sugar Metabolism in Hummingbirds and Nectar Bats.

Hummingbirds and nectar bats coevolved with the plants they visit to feed on floral nectars rich in sugars. The extremely high metabolic costs imposed by small size and hovering flight in combination with reliance upon sugars as their main source of dietary calories resulted in convergent evolution of a suite of structural and functional traits. These allow high rates of aerobic energy metabolism in the flight muscles, fueled almost entirely by the oxidation of dietary sugars, during flight. High intestinal sucrase activities enable high rates of sucrose hydrolysis. Intestinal absorption of glucose and fructose occurs mainly through a paracellular pathway. In the fasted state, energy metabolism during flight relies on the oxidation of fat synthesized from previously-ingested sugar. During repeated bouts of hover-feeding, the enhanced digestive capacities, in combination with high capacities for sugar transport and oxidation in the flight muscles, allow the operation of the “sugar oxidation cascade”, the pathway by which dietary sugars are directly oxidized by flight muscles during exercise. It is suggested that the potentially harmful effects of nectar diets are prevented by locomotory exercise, just as in human hunter-gatherers who consume large quantities of honey.

Ramping of pH Across the Water-Pool of a Reverse Micelle.

In this work, we have addressed the problem of "acidity" of the water-pool of a reverse micelle (RM) through the well-known inversion of sucrose reaction as a tool of investigation. This reaction has been performed inside positively and negatively charged RM and the rates are compared with that in bulk water. We propose that the buffer-like action in a water-pool is much stronger than expected earlier. The rate of sucrose hydrolysis slowed down in the negatively charged AOT reverse micelle while it sped up for the positively charged CTAB reverse micelle. However, temperature-dependent measurements showed that the activation energy remained the same for all the cases. It has been concluded that a proton gradient exists inside the water-pool of the reverse micelle and it determines the buffer-like action of the water-pool that persists until about 2 N of HCl in AOT RM of w(0) = 10.5.

Catalytic consequences of micropore topology, mesoporosity, and acidity on the hydrolysis of sucrose over zeolite catalysts

The effects of zeolite micropore topology, mesoporosity, and acidity on the hydrolysis of polysaccharides were probed in reactions of sucrose over a variety of zeolite catalysts (FER, MFI, MOR, MWW, BEA, FAU, pillared MFI (PMFI), and pillared MWW (PMWW)). The measured rate of sucrose hydrolysis over microporous zeolites varied by a factor of ~100 following a trend of FER < MOR ~ MFI < BEA ~ MWW < FAU, indicating that the hydrolysis of sucrose increases with increasing zeolite micropore sizes. The presence of mesoporosity in PMFI and PMWW zeolites enhanced the rates of sucrose reactions by a factor of ~2 in comparison with the microporous MWW and MFI zeolites, which may result from the enhanced acid site accessibility and mitigated diffusion constraints. The examination on the effects of zeolite acidity on the hydrolysis of sucrose by employing MFI, PMFI, BEA, MWW, and FAU zeolites with a range of Si/Al ratios showed that a Si/Al ratio of ~70–150 provides a maximal rate constant per acid site in the catalysts. The measured activation energies of the catalytic reactions in all zeolites were similar. The measured entropies, however, increased abruptly with increasing micropore sizes of zeolites and slightly with increasing mesoporosity in the zeolites. The present study suggests that the hydrolysis of sucrose is driven primarily by the reaction entropies that are dominated consecutively by the micropore topology, acidity, and mesoporosity of the zeolite catalysts.

The stimulatory effect of mannitol on levan biosynthesis: Lessons from metabolic systems analysis of Halomonas smyrnensis AAD6T

Halomonas smyrnensis AAD(T) is a halophilic, gram-negative bacterium that can efficiently produce levan from sucrose as carbon source via levansucrase activity. However, systems-based approaches are required to further enhance its metabolic performance for industrial application. As an important step toward this goal, the genome-scale metabolic network of Chromohalobacter salexigens DSM3043, which is considered a model organism for halophilic bacteria, has been reconstructed based on its genome annotation, physiological information, and biochemical information. In the present work, the genome-scale metabolic network of C. salexigens was recruited, and refined via integration of the available biochemical, physiological, and phenotypic features of H. smyrnensis AAD6(T) . The generic metabolic model, which comprises 1,393 metabolites and 1,108 reactions, was then systematically analyzed in silico using constraints-based simulations. To elucidate the relationship between levan biosynthesis and other metabolic processes, an enzyme-graph representation of the metabolic network and a graph decomposition technique were employed. Using the concept of control effective fluxes, significant links between several metabolic processes and levan biosynthesis were estimated. The major finding was the elucidation of the stimulatory effect of mannitol on levan biosynthesis, which was further verified experimentally via supplementation of mannitol to the fermentation medium. The optimal concentration of 30 g/L mannitol supplemented to the 50 g/L sucrose-based medium resulted in a twofold increase in levan production in parallel with increased sucrose hydrolysis rate, accumulated extracellular glucose, and decreased fructose uptake rate.

SUCROSE INVERSION OF HARD CANDIES FORMULATED WITH REWORK SYRUP WITH ADDITION OF SODIUM LACTATE

ABSTRACT This work investigated the use of rework syrup with addition of sodium lactate in hard candy manufacturing, following the inversion of sucrose in hard candies where 10% of the glucose syrup of the formulation was substituted by the rework syrup. Moisture, mass net gain, water activity and visual inspection of crystallization and cold melt were carried out in the final product. The candies prepared with rework syrup with up to 4 g of sodium lactate solution/100 g presented lower pH, decrease of sucrose content and increase in glucose and fructose concentrations. The increase in fructose content was followed by an increase in net weight of the candies, inducing crystallization and cold melt. The addition of 2 g of sodium lactate/100 g in the rework syrup and 2/100 g in the final syrup before cooking was effective in reducing inversion of sucrose. PRACTICAL APPLICATIONSThe occurrence of products that are out of specification is common in manufacturing hard candy. Usually, these products are dissolved again in water and are filtered, the aroma and dyes are removed and the resulting syrup, called rework syrup, is used in the preparation of new sucrose syrup for hard candy production. However, the addition of rework syrup to the formulation of new candies creates a problem, as the sucrose in this syrup may have been partially hydrolyzed, yielding glucose and fructose. The resulting hard candy would then have a high fructose content, which will induce crystallization and cold melt of the candy, decreasing its shelf life. The results of this work show that the rework syrup could be improved by the addition of a buffering agent, sodium lactate, which decreases the rate of sucrose hydrolysis, improving the quality of the resulting candies, as well as their shelf life.

Kinetics of Moisture-Induced Hydrolysis in Powder Blends Stored at and below the Deliquescence Relative Humidity: Investigation of Sucrose−Citric Acid Mixtures

Previous studies have shown that deliquescent organic compounds frequently exhibit chemical instability when stored in environmental conditions above their deliquescence relative humidity (RH). The goal of the current study was to investigate the effect of atmospheric moisture on the long-term chemical stability of crystalline sucrose-citric acid mixtures following storage at RHs at and below the mutual deliquescence relative humidity (MDRH). Interestingly, it was found that sucrose hydrolysis can occur below the MDRH of 64% and was observed for samples stored at 54% RH. However, hydrolysis was not seen for samples stored at 33 or 43% RH. The rate of sucrose hydrolysis could be modeled by taking into account the rate and extent of moisture uptake, which in turn was dependent on the composition of the powder and the storage RH. A reaction mechanism initiated by capillary condensation and involving additional deliquescence lowering by the degradation products formed as a result of sucrose hydrolysis (glucose and fructose) was proposed.

Catalytic production of hydroxymethylfurfural from sucrose using 1-methyl-3-octylimidazolium chloride ionic liquid

Hydroxymethylfurfural (HMF) is an important chemical intermediate, but it has not been widely used be- cause of low yields and high production costs. Sucrose is available at lower costs than other sugars and thus could be a biomass-derived abundant source for HMF production. In this study, a catalytic process for efficiently producing HMF from sucrose was scrutinized using 1-methyl-3-octylimidazolium chloride ((MOIM)Cl) as a reaction solvent, and HCl and metal chlorides (CrCl2 and Zncl2) as a catalyst. The rate of sucrose hydrolysis was relatively much faster in the reactions with HCl than without it. The hydrolysis of sucrose to fructose and glucose was affected by its reaction time. The mixed solvent of 50% (MOIM)Cl and 50% sucrose solution with HCl was more effective in HMF synthesis than single solvent alone. The addition of ZnCl2 and CrCl2 increased HMF yields by approximately 1.2-1.8-fold and its higher yield was found in the latter. The highest yield (82.0±3.9 wt%) in HMF production was achieved in the reaction mixture containing 5 g (MOIM)Cl and 5 mL of 20% sucrose solution with 0.5 M HCl plus CrCl2 at 30 min reaction time. How- ever, 0.3 M HCl was more effective for the HMF productivity than 0.5 M HCl.

Cocoa polyphenols inhibit sucrose hydrolysis in Caco‐2 cells

Disaccharidase enzymes bound to the microvilli of intestinal epithelial cells are essential in the liberation of glucose from dietary carbohydrates. Glucose uptake from the lumen of the small intestine is facilitated by transporters located in the apical membrane of enterocytes; subsequent diffusion into capillary blood occurs at the basolateral surface similarly facilitated by transporters.Attenuation of enzyme and transporter activity may decrease post‐prandial blood glucose levels thereby providing a more uniform supply of glucose to the cells rather than an initial peak followed by rapid decline. This may have positive consequences not only for healthy subjects but also for individuals suffering from impaired glucose tolerance and type‐2 diabetes.Using Caco‐2 cells, passages 36 to 40, the rate of sucrose hydrolysis has been determined in the absence and presence of cocoa extracts and various polyphenols present in chocolate and cocoa. Using sucrose as the substrate, kinetic parameters were: a maximum reaction rate (Vmax) of 4.5 μmol min−1 and a Michaelis‐Menten constant (Km) of 33 mM.The addition of cocoa extract inhibited sucrose hydrolysis by Caco‐2 cells. (−)‐Epicatechin, (+)‐catechin and procyanidin B2, major components of cocoa, also diminished sucrose hydrolysis in Caco‐2 cells substantially.These results show that intestinal hydrolysis of sucrose by alpha‐glucosidase enzymes may be inhibited by cocoa polyphenols thereby reducing the rate of liberation of glucose. This would subsequently limit the uptake of glucose into the blood thereby reducing post‐prandial blood glucose levels.This work was funded by a BBSRC industrial case award to Nestlé, York UK.

The intake responses of three species of leaf-nosed Neotropical bats

Flower-visiting bats encounter nectars that vary in both sugar composition and concentration. Because in the new world, the nectars of bat-pollinated flowers tend to be dominated by hexoses, we predicted that at equicaloric concentrations, bats would ingest higher volumes of hexoses than sucrose-containing nectars. We investigated the intake response of three species of Neotropical bats, Leptonycteris curasoae, Glossophaga soricina and Artibeus jamaicensis, to sugar solutions of varying concentrations (292, 438, 584, 730, 876, and 1,022 mmol L(-1)) consisting of either sucrose or 1:1 mixtures of glucose and fructose solutions. Bats did not show differences in their intake response to sucrose and 1:1 glucose-fructose solutions, indicating that digestion and absorption in bat intestines are designed under the principle of symmorphosis, in which no step is more limiting than the other. Our results also suggest that, on the basis of energy intake, bats should not prefer hexoses over sucrose. We used a mathematical model that uses the rate of sucrose hydrolysis measured in vitro and the small intestinal volume of bats to predict the rate of nectar intake as a function of sugar concentration. The model was a good predictor of the intake responses of L. curasoae and G. soricina, but not of A. jamaicensis.

Downregulation of neutral invertase activity in sugarcane cell suspension cultures leads to a reduction in respiration and growth and an increase in sucrose accumulation

Suspension cultures were used as a model system to investigate sucrose metabolism in four sugarcane (Saccharum spp. interspecific hybrids) cell lines transformed with antisense neutral invertase (NI) constructs. Throughout a 14-day growth cycle two cell lines in which the antisense sequence was under the control of a tandem CaMV-35S: maize ubiquitin promoter showed a strong reduction in NI activity, as well as reduced hexose and increased sucrose concentrations in comparison to the control line. In lines where the antisense NI sequence was under the control of the weaker CaMV-35S promoter alone, changes in enzyme activity and sugar concentrations were intermediate to those of the more strongly inhibited lines and the control. In comparison to the control line, a higher sucrose to hexose ratio, i.e. increased purity, was obtained in all the lines with reduced NI activity. The in vivo rate of sucrose hydrolysis was reduced in the transgenic lines, suggesting a concomitant reduction in the flux through the 'futile cycle' of sucrose breakdown and re-synthesis. Differences between the transgenic cultures and the control were most pronounced during the early stages of the growth cycle and tapered off as the cultures matured. The transgenic cultures displayed impaired growth characteristics suggesting that the growth rate of these cells was retarded because of the reduced availability of hexoses for respiration.

Physiological Constraint to Food Ingestion in a New World Nectarivorous Bat

We investigated the intake response of the nectarivorous Pallas's long-tongued bat Glossophaga soricina to different nectar concentrations to test the hypothesis that bats show compensatory feeding. Bats were offered sucrose solutions between 146 and 1,168 mmol L(-1). Contrary to our expectations, long-tongued bats did not show compensatory feeding, suggesting that volumetric food intake is physiologically constrained. Energy intake was lower at the most dilute solutions (146-584 mmol L(-1)) and then remained relatively constant at more concentrated diets (876 and 1,168 mmol L(-1)). The shape of the observed intake response was very similar to the one predicted by a model dependent on intestinal morphology and in vitro sucrase activity. However, the model predicted higher volumetric food intake at the lower concentrations tested, which suggests that the intestines of the bats were not functioning to their full capacity. Rates of sucrose hydrolysis and water processing probably constrain food intake in long-tongued bats as diets get more dilute.

A Survey of Industrial Strains ofSaccharomyces cerevisiaeReveals Numerous Altered Patterns of Maltose and Sucrose Utilisation

A model fermentation system was used to define the abilities of 25 Saccharomyces cerevisiae strains, representing the brewing, baking, winemaking and distilling industries, to utilise maltose and sucrose in the presence of glucose and fructose. Three categories of sucrose and maltose utilisers were observed; repressible, constitutive and non-utilisers. In terms of fermentation kinetics, neither high rates of sucrose hydrolysis nor the early onset of maltose utilisation were correlated with reduced fermentation duration in the experimental system used. Instead better positive correlations were found between this parameter and biomass formation (R2 = 0.62) and rates of maltose or monosaccharide removal (R2 = 0.87 and 0.82, respectively). Additionally, invertase activity of brewing strains was seen to occur in two forms: cell-associated and non-cell-associated. This survey exposed a number of novel phenotypes that could be harnessed as a means of producing strains with rapid and efficient utilisation of fermentable carbohydrates.

The effect of inoculum density and conditioned medium on the production of ajmalicine and catharanthine from immobilizedCatharanthus roseus cells

The effect of the cell-inoculum size and the addition of conditioned medium on ajmalicine and catharanthine production were studied using immobilized Catharanthus roseus cells. Higher specific-uptake rates of ammonium, nitrate, and sugars were observed in the low-inoculum-density cultures (50 g FW/L) compared to the high-inoculum-density cultures (100 g FW/L). Alkaloid production was not correlated with the exhaustion of a particular nutrient from the medium. The high-inoculum-density cultures produced higher ajmalicine concentrations throughout the experiment. Catharanthine production was similar between the two inoculum-density cultures. The addition of conditioned medium to MS-production medium dramatically improved the production of ajmalicine and catharanthine. The addition of conditioned medium enhanced ajmalicine production from immobilized Catharanthus roseus cultures on day 15 by at least two- to fourfold compared to media without the conditioning factors. Catharanthine production was increased by nearly fivefold in cultures with conditioned medium compared to those without conditioned medium. The enhancing effects of conditioned medium on alkaloid production were attributed to an unidentified factor produced and secreted by suspension cultures of C. roseus. The presence of conditioned medium also decreased the sucrose hydrolysis rate. The ajmalicine concentration in these immobilized cell cultures was found to be a function of the fresh-weight concentration, irrespective of the inoculum density or the culture medium. The medium choice and the inoculum density determined how rapidly fresh weight was accumulated and thus, how quickly ajmalicine was produced. Ajmalicine production correlated positively with fresh-weight concentration, but catharanthine production was not correlated with fresh-weight concentration.