Low Sucrose Concentrations Research Articles

The establishment of callus and cell suspension cultures of Hylocereus costaricensis for the production of betalain pigments with antioxidant potential

Hylocereus costaricensis, commonly known as red-purple dragon fruit or pitaya, is a climbing vine cactus that is currently widely grown as a fruit crop and has gained popularity as a potential source of both natural colourants and antioxidants contributed by betalain compounds. Betalains comprised of red-purple betacyanins and yellow betaxanthins. This study aimed to establish callus and cell suspension cultures of H. costaricensis from in vitro germinated seedlings and to evaluate their betalain content and antioxidant profiles. Epicotyl and cotyledon segments of 60-day-old axenic seedlings were examined for their callus induction potential on half-strength Murashige and Skoog (MS) medium supplemented with various concentrations of naphthaleneacetic acid (NAA) and Thidiazuron (TDZ) under different illumination (16-h photoperiod and darkness). Different combinations of picloram and 2,4-dichlorophenoxyacetic acid (2,4-D) were subsequently tested for the induction of friable callus. The betalains, total phenolic content, total flavonoid content and antioxidant activity DFRSA in cell suspension cultures were quantified using spectrophotometric analysis. Generally, cotyledon explants cultured under 16-h photoperiod was optimum for callus induction. Compact callus with roots was formed on medium supplemented with NAA while granular callus was formed in TDZ supplemented medium. Among the 36 treatments tested, supplementation of 10 μM picloram induced friable callus with average fresh mass of 0.817 g (10.2-fold as compared to the control treatment). Picloram at 10 μM concentration was also found to be effective for callus proliferation and initiation of cell suspension culture. Yellow and red callus were produced and proliferated on the same medium through repetitive clonal selection. The higher concentration of sucrose was more effective for cell mass accumulation while lower sucrose concentration stimulated the accumulation of betalain compounds and antioxidants in the cell suspension cultures of H. costaricensis. This study indicates that callus and cell suspension culture could be used as an efficient system for sustainable production of betalain compounds which can contribute to functional food colouring and pharmaceutical industries.

Production of potato (Solanum tuberosum, L.) microtubers using plastic culture bags.

We have developed a system using plastic culture bags with forced aeration system for both liquid medium and gaseous phase to produce microtubers of potato (Solanum tuberosum L.). The production of microtubers under sterile conditions is a good way to produce disease-free materials for crop production, and bioreactors have been used for this purpose. However, bioreactors are expensive and difficult to handle. The plastic culture bags are relatively inexpensive and are easy to store and sterilize because they can be flattened. Microtuber production involves two stages: plant proliferation in one medium, followed by microtuber production in a different medium. Both steps are carried out using the same culture bag. Using this system, we produced 100 to 300 microtubers per 8 l culture bag, depending on the potato cultivar. We varied the nutrient concentrations in the media and found that a lower sucrose concentration in the plant proliferation medium and lower nitrogen concentration in the microtuber production medium both increased the total numbers of microtubers per bag. Notably, a higher concentration of potassium phosphate increased the numbers of larger microtubers. This is beneficial because larger microtubers are much more tolerant to field conditions. We produced about 250,000 microtubers per year in a 66 m2 tissue culture room using the culture bag system. These microtubers have been planted directly in the field and utilized for seed potato production.

Preparation of a Millimeter-Sized Supergiant Liposome That Allows for Efficient, Eukaryotic Cell-Free Translation in the Interior by Spontaneous Emulsion Transfer.

We sought to prepare millimeter-sized supergiant unilamellar vesicles (SGUVs) by spontaneous emulsion transfer for efficient, eukaryotic cell-free translation in the interior. Although the conventional protocols require that a considerably high concentration of sucrose be encapsulated into the SGUVs for their efficient formation, such high amounts of sucrose severely inhibited cell-free translation based on wheat germ extract (WGE). We thus optimized the preparation conditions to permit SGUV formation at a much lower concentration of sucrose that has almost no effect on WGE translation. Under the optimized conditions, we successfully prepared WGE translation system-encapsulating SGUVs that allow for protein synthesis with a high efficiency comparable to that outside a liposome. The optimization also resulted in a high rate of successful SGUV formation (>90%) and a decent stability of the formed SGUVs (>60 min). These SGUVs are expected to serve as research tools in cell-free synthetic biology and as foundations for artificial cell-based biosensors.

Viscous Media Slow Down the Decay of the Key Intermediate in Bacterial Bioluminescent Reaction.

The effects of medium viscosity on the decay rate of the 4a-hydroperoxyflavin intermediate of the bioluminescent reaction was investigated. It was found that at low concentrations of glycerol or sucrose (viscosity 1.1-1.3 cP) the decay rate rises, whereas a further increase in viscosity to 6.2 cP leads to a decrease in the decay rate following a power function with an exponent of 0.82-0.84. Using molecular dynamics methods, it was shown that the presence of glycerol and sucrose molecules causes a change in the mobility of the amino acid residues in the active center of luciferase, particularly those responsible for binding of flavin. The results obtained are indicative of two opposite effects of viscous media with glycerol and sucrose: (1) destabilization of 4a-hydroperoxyflavin due to a change in the structural and dynamic properties of the protein and (2) stabilization of this intermediate by the decrease in the diffusion rate of its decay products.

A novel sucrose transporter gene IbSUT4 involves in plant growth and response to abiotic stress through the ABF-dependent ABA signaling pathway in Sweetpotato

BackgroundTo maintain sweetpotato (Ipomoea batatas (L.) Lam) growth and yield, sucrose must be transported from the leaves to the roots. Sucrose transporters or carriers (SUTs or SUCs) transport sucrose and are involved in plant growth and response to abiotic stress. However, the mechanisms of SUTs in sweetpotato abiotic stress resistance remains to be determined.ResultsIn the present study, we cloned a novel IbSUT4 gene; the protein encoded by this gene is localized in the tonoplast and plasma membrane. The plant growth was promoted in the IbSUT4 transgenic Arabidopsis thaliana lines, with increased expression of AtFT, a regulator of flowering time in plants. Over-expression of IbSUT4 in Arabidopsis thaliana resulted in higher sucrose content in the roots and lower sucrose content in the leaves, as compared to the wild-type (WT) plants, leading to improved stress tolerance during seedling growth. Moreover, we systematically analyzed the mechanisms of IbSUT4 in response to abiotic stress. The results suggest that the ABRE-motif was localized in the IbSUT4 promoter region, and the expression of the ABA signaling pathway genes (i.e., ABF2, ABF4, SnRK2.2, SnRK2.3, and PYL8/RCAR3) were induced, and the expression of ABI1 was inhibited.ConclusionsOur dates provide evidence that IbSUT4 is not only involved in plant growth but also is an important positive regulator in plant stress tolerance through the ABF-dependent ABA signaling pathway.

Elevation of the Blood Glucose Level is Involved in an Increase in Expression of Sweet Taste Receptors in Taste Buds of Rat Circumvallate Papillae.

The gustation system for sweeteners is well-known to be regulated by nutritional and metabolic conditions, but there is no or little information on the underlying mechanism. Here, we examined whether elevation of the blood glucose level was involved in alteration of the expression of sweet taste receptors in circumvallate papillae (CP) and sweet taste sensitivity in male Sprague-Dawley rats. Rats under 4 h-fed conditions following 18 h-fasting exhibited elevated blood glucose levels and decreased pancreatic T1R3 expression, compared to rats after 18 h-fasting treatment, and they exhibited increased protein expression of sweet taste receptors T1R2 and T1R3 in CP. Under streptozotocin (STZ)-induced diabetes mellites (DM) conditions, the protein expression levels of T1R2 and T1R3 in CP were higher than those under control conditions, and these DM rats exhibited increased lick ratios in a low sucrose concentration range in a brief access test with a mixture of sucrose and quinine hydrochloride (QHCl). These findings indicate that the elevation of blood glucose level is a regulator for an increase in sweet taste receptor protein expression in rat CP, and such alteration in STZ-induced DM rats is involved in enhancement of their sweet taste sensitivity.

Effects of culture medium composition and PEG on hyperhydricity in Dendrobium officinale

Hyperhydricity is a physiological disorder during plant tissue culture that seriously affects regeneration and micropropagation. In this study, Dendrobium officinale plantlets were cultured on solid Murashige and Skoog (MS) medium supplemented with plant growth regulators and various concentrations of sucrose, agar, and polyethylene glycol (PEG)-6000 to explore the effect of osmotic stress on hyperhydricity. The results show that low concentrations of sucrose or agar, as well as PEG-6000 at various concentrations, significantly increase the hyperhydric rate of D. officinale, whereas high concentrations of sucrose or agar did not. Furthermore, high concentrations of PEG-6000 significantly increase total water content, free-water content, relative electrical conductivity, and peroxidase (POD) activity of D. officinale plantlets, whereas they significantly decrease bound-water content, proline content, soluble protein content, soluble sugar content, and superoxide dismutase (SOD) activity. These results indicate that PEG-6000 disrupts the antioxidant system and water metabolism in D. officinale plantlets, as well as increases cell membrane permeability, which might be the key factors for the occurrence of hyperhydricity in this species.

Micropropagation, encapsulation, and conservation of Decalepis salicifolia, a vanillin isomer containing medicinal and aromatic plant

An efficient in vitro propagation and synthetic seed production protocol was established for the conservation of Decalepis salicifolia (Bedd. ex Hook.f.) Venter, an endemic and critically endangered ethnomedicinal species. Murashige and Skoog (MS) media supplemented with 2.2 μM BAP and 5.7 μM IAA produced shoot tip proliferation with an average shoot length of 5.81 ± 0.03 cm in 3 wk. Axillary bud proliferation was found to be best in 11.1 μM BAP with an average of 3.5 ± 0.06 shoots per explant. Shoot tip and nodal explants were encapsulated in sodium alginate and their regeneration was achieved following storage at 4°C up to 12 wk. Successful rooting was obtained in modified MS medium with low nitrate and high sucrose concentration. Quarter strength MS media containing 2.5 mM each of NH4NO3 and KNO3 along with 8% sucrose produced an average number of 12.4 ± 1.18 roots with an average length of 4.3 ± 0.08 cm. The in vitro derived rooted plants were successfully hardened (92.8%) and established in field with 100.0% survival rate. Inter-simple sequence repeat (ISSR) markers proved the genetic fidelity among the in vitro grown plant showing 99.5% similarity with the mother plant. Micropropagation derived acclimatized plants produced 2-hydroxy-4-methoxybenzaldehyde in amounts similar to seed-derived field-grown plants of the same age. The in vitro propagation protocol developed for D. salicifolia can be utilized to reduce exploitation pressure from their natural habitats and augment ecorestoration, conservation, and cultivation of this critically endangered and industrially valuable plant. The synthetic seeds technique will serve as propagules in ex situ gene banks, as well as supports cost-effective germplasm conservation.

Sweetness Enhancement by Aromas: Measured by Descriptive Sensory Analysis and Relative to Reference Scaling.

Sweetness enhancement by aromas has been suggested as a strategy to mitigate sugar reduction in food products, but enhancement is dependent on type of aroma and sugar level. A careful screening of aromas across sugar levels is thus required. Screening results might, however, depend on the method employed. Both descriptive sensory analysis and relative to reference scaling were therefore used to screen 5 aromas across 3 sucrose concentrations for their sweetness-enhancing effects in aqueous solutions. In the descriptive analysis, samples with added vanilla, honey, and banana aroma were rated as significantly sweeter than samples with added elderflower or raspberry aroma at all sucrose concentrations. In relative to reference scaling, honey aroma significantly increased the sweet taste compared with samples with added elderflower or no aroma at low and medium sucrose concentrations. Banana and raspberry aromas also increased the sweet taste significantly compared with the sample with added elderflower aroma at medium sucrose concentration in the relative to reference scaling. This demonstrates that the cross-modal effects observed by the 2 methods were different. In terms of the methods applied, relative to reference scaling was generally found to result in a decrease in the measured sweetness enhancement by aromas. In the descriptive analysis, the cross-modal effect of aromas on sweet taste perception was found to be significantly higher at 2.5% and 5.0% w/w sucrose compared with 7.5% w/w sucrose. These results highlight the importance of considering how references are employed in sensory analysis and how they affect cross-modal interactions.

Chemical kinetics, thermodynamics and inactivation kinetics of dextransucrase activity by ultrasound treatment

In this work, the impact of ultrasound on dextransucrase activity was investigated, and a biphasic model was introduced to investigate the inactivation kinetics of the dextransucrase catalytic reaction. In addition, a chemical kinetic model, the Michaelis–Menten equation, Eyring transition state theory and the Arrhenius equation were applied. Short periods of exposure to low-intensity ultrasound significantly increased the activity of dextransucrase. The maximum activity was 1.25 ± 0.01 u/mL at an ultrasound intensity of 1.8 W/cm3 for 3 min, which was 27.6% higher than the activity of the untreated enzyme (0.98 ± 0.038 U/mL). In addition, after the ultrasound treatment, the kinetic model of the dextransucrase catalytic reaction was fitted to a first-order kinetic model at low sucrose concentrations. At low sucrose concentrations, the Ea, ΔH, ΔS and ΔG of ultrasound-treated dextransucrase were reduced by 33.7, 35.7, 28.8 and 0.38%, respectively. Furthermore, compared with the parameters of the untreated sample, the value of Vmax the treated sample increased, and Km decreased. The thermal inactivation model of the dextransucrase catalytic reaction in a shaker was fitted to a biphasic model, and the percentage of the thermally stable fraction of ultrasound-treated dextransucrase was increased, while the rate of deactivation was decreased. Moreover, the degree of thermal inactivation was inversely proportional to the dextransucrase concentration. The fluorescence spectra showed a decrease in the amount of tryptophan on the surface of dextransucrase treated with ultrasound. In conclusion, short-term treatment with low ultrasound intensity increases the activity, thermal stability and reaction rate of dextransucrase.

Drought effects on cotton (Gossypium hirsutum L.) fibre quality and fibre sucrose metabolism during the flowering and boll‐formation period

AbstractThe cotton (Gossypium hirsutum L.) crop is an indeterminate species that is most sensitive to drought stress during the flowering and boll‐formation stage of development. To evaluate the effect of water deficit on fibre quality and carbon metabolism at different fruiting branches (FB), multiple controlled experiments were conducted. The cotton cultivar Siza 3 was used under three soil relative water content (SRWC): control (CK, SRWC (75 ± 5) %), moderate drought stress (MDS, SRWC (60 ± 5) %) and severe drought stress (SDS, SRWC (45 ± 5) %) treatment, imposed at the beginning of the flowering of FB6–7. Fibre quality was significantly affected by drought level and fruiting branch location on the plant. Compared to the CK, under MDS and SDS, sucrose content and sucrose synthase (SuSy) activity decreased prior to 24 days post‐anthesis (DPA; the fibre elongation phase), which caused low fibre turgor pressure. This decreased the rate of fibre elongation and final fibre length. Moreover, from 24 to 38 DPA (during fibre thickening), low fibre sucrose content led to insufficient UDP‐glucose (UDPG; uridine diphosphate glucose) for cellulose synthesis. Furthermore, more of the existing UDPG was allocated to the synthesis of callose instead of cellulose, which resulted in lower cellulose accumulation and decreased fibre strength. The magnitude of the drought stress effect on fibre qualities, as well as the formation process, was strongly influenced by fruiting branch position, where differences were most pronounced for fruiting branches further away from the base of the plant.

At-harvest fruit maturity affects sucrose metabolism during cold storage and is related to chilling injury in peach.

We investigated the effects of at-harvest maturity of 'YuLu' peach fruit on soluble sugar metabolism and their relationship with chilling injury susceptibility. Peaches were sorted into four maturity groups at harvest by I AD (index of the absorbance difference between 670 and 720nm) then stored at 5°C for 28days. Fruit quality parameters, flesh browning index, malondialdehyde (MDA) content, soluble sugar content, gene expression, and enzyme activities associated with sucrose metabolism were measured. The more mature fruit groups had significantly (p < 0.05) lower firmness, higher soluble solid content, a* values of background color, sorbitol and sucrose content at harvest. During the cold storage, the higher flesh browning index in the mature groups (M3 and M4) maybe due to the double stress of senescence and chilling injury because there was concomitant sharp increase in MDA content. However, the most immature at-harvest group (M1) had the significantly (p < 0.05) higher MDA content after 14days of cold storage, and a flesh browning index significantly (p < 0.05) higher than the M2 group (the next more mature group), late in the storage period. Moreover, the M1 group had lower sucrose content at postharvest and higher activities and transcript levels of sucrose degrading enzymes and lower levels of sucrose synthesis enzymes, which was responsible for the lower sucrose levels than M2 group during storage. It was concluded that the more immature peach fruit with lower sucrose content, have a higher chilling susceptibility than more mature fruit.

Reuteransucrase-catalytic kinetic modeling and functional characteristics for novel prebiotic gluco-oligomers.

This work describes the reuteransucrase-catalyzed reaction and structural characterization as well as in vitro fermentation for the acceptor products of gluco-oligomers from sucrose and maltose. At a low concentration of sucrose, the production of gluco-oligomers was favored, resulting in a relatively large number of acceptor products (DP3-5). A mathematical model was also proposed to simulate gluco-oligomer production depending on the reaction conditions. The fine structures of major linear gluco-oligomer fractions for a sucrose : maltose ratio of 1 : 1 were assigned as follows: α-d-Glcp-(1→6)-α-d-Glcp-(1→4)-d-Glcp, α-d-Glcp-(1→4)-α-d-Glcp-(1→4)-α-d-Glcp-(1→4)-d-Glcp, α-d-Glcp-(1→4)-α-d-Glcp-(1→6)-α-d-Glcp-(1→4)-d-Glcp, and α-d-Glcp-(1→6)-α-d-Glcp-(1→4)-α-d-Glcp-(1→6)-α-d-Glcp-(1→4)-d-Glcp, respectively. Compared with dextran and GOS57, the results of fermentation selectivity indicated that gluco-oligomers promoted the proliferation of gut bacteria and total SCFA production with a higher concentration of propionate. These data suggested that the gluco-oligomers synthesized via the reuteransucrase acceptor reaction had a prebiotic effect on gastrointestinal health.

Evaluation of sucrose as carbon source in mixotrophic culture of Arthrospira platensis Gomont 1892

Cyanobacteria are photosynthetic microorganisms that use CO 2 as carbon source and sunlight as energy source. Although phototrophic cultivation is widely used in cyanobacterium production, heterotrophic and mixotrophic cultivations attract attention among researchers. In this study the effect of different concentrations (0[control] - 0.25 - 2.5 - 10 - 50 mM) of sucrose on the growth of Arthrospira platensis under mixotrophic cultivation was investigated. The purpose of this study was to investigate whether A. platensis biomass production could be performed regardless of high light intensity. Biomass, chlorophyll, lipid and carbohydrate contents were determined by spectrophotometrically. Also the physicochemical properties of the produced cyanobacterium were investigated by FTIR, TGA and DSC. The highest biomass productivity was detected as 1.33 g/L/day in the medium containing 2.5 mM sucrose and the specific growth rate increased 1.32 fold as compared to phototrophic culture. Additionally, t he highest lipid content (3.68 ±0.17 mg/g cell) was determined in the same medium. This suggests that A. platensis has adapted to the medium that contains low sucrose concentrations. Also, this study showed that sucrose containing medium supports lipid production.

Unravelling Sugar Accumulation in Sugarcane (Saccharum spp.) Stalk: Recent Approaches

Sucrose accumulation in developing sugarcane (Saccharum officinarum) is accompanied by a continuous synthesis and cleavage of sucrose in the storage tissues. It is synthesized in source mature leaves and such assimilates stored in the form of sucrose in the stalks of sugarcane that provide 70% of world sugar. During the phloem transportation, sucrose is unloaded into the sink for metabolism and storage. Its accumulation in sugarcane stalks is affected by sucrose supply, metabolism and sink strength. Sucrose accumulation and carbohydrate metabolism in plant species depend upon activity of Sucrose Synthase (SuSy) enzyme. Fast growing tissues in sugarcane such as root apices, immature stem internodes, cells and tissue cultures usually have low sucrose and higher concentration of SAI (soluble acid invertase) which hydrolyses sucrose into glucose and fructose. The sugar yield needs its enhancement to meet the growing demand for sugar. The photosynthesis activity in source leaves decides the amount of sucrose to sink organs. Sucrose metabolism enzymes control sucrose content in sugarcane stalks. Sucrose accumulation is a complex physiological process controlled by network genes. Recent biochemical and molecular approaches have resolved the various developmental and molecular regulation mechanisms for sucrose accumulation in sugarcane. In this review, discussion have been focussed on molecular involved in sucrose metabolism, source-sink communication and storage, microarray analysis, expressed sequence tags (ESTs) studies, physiological and tissue-specific gene regulation that will help further researches to elucidate the regulatory networks of sucrose accumulation to breed high sugar content in sugarcane.

Effect of short-term intake of high- and low-concentrations of sucrose solution on the neurochemistry of male and female mice.

The effect of short-term intake of high- and low-concentrations of sucrose solution on the neurochemistry of male and female mice was studied. The body weight, feed intake, sucrose solution consumption and brain monoamine neurotransmitters were determined after 34 days' intake of 1% and 8% sucrose solutions. The gene expression and protein levels related to dopamine and opioids were also determined. The results showed that the intake of 1% and 8% sucrose solution for 34 days did not cause significant changes in the weight development of both male and female mice. The preference for sucrose varies with sex. Both males and females had greater preference for the high concentration sucrose solution than the low concentration sucrose solution. The continuous intake of sucrose stimulated the release of monoamine neurotransmitters (DA, 5-HT, NE) in the brains of mice, and the reward effect of 8% sucrose solution is significantly higher than that of 1% sucrose solution. The sex of mice did not affect the release of neurotransmitters. The gene expressions of D1 and D2 were up-regulated in the 1% sucrose group of male mice, while the OPRM1 gene expression was down-regulated. The expression of these three genes in the 8% sucrose group of male mice was all down-regulated, while the gene expressions of D1 and D2 in the 1% and 8% sucrose group (p < 0.05) of female mice were both up-regulated.

Influence of Dextransucrase of Weissella Cibaria Nitcsk4 on Low Molecular Weight Dextran Yield: a Statistical Approach using Mixed Level Taguchi Design and Artificial Neural Network

In the present study, the influence of dextransucrase of Weissella cibaria NITCSK4 (DSWc4), sucrose concentration, and reaction temperature on the yield of low molecular weight dextran (LMWD-DexWc4) was investigated using mixed level Taguchi design and back propagation neural network (BPNN). BPNN model with three neurons in a hidden layer generated a low mean squared error (MSE). The determination coefficients (R2 -value) for ANN and Taguchi models were 0.991 and 0.998, respectively. Considering absolute average deviation (AAD) and MSE, Taguchi model is more adequate. Among three factors, the percentage yield of low molecular weight of dextran is invariably dependent on the sucrose concentration. The study suggested that a low sucrose concentration (3% w/v), DSWc4 (0.25 IU/ml) and slightly high temperature (35°C) ultimately favored the production of LMWD-DexWc4 (91.639%). LMW-DexWc4 produced by DSWc4 at optimized conditions was analyzed. The weight average molecular weight of LMW-DexWc4 was calculated using M-H expression, found to be 85775 (≈90 kDa). The relative percentage error between the number and weight average molecular weight was found to be less (4.42%). The polydispersity (PD) index of the LMW-DexWc4 was found to be 0.9576 and the value is close to 1. The PD value depicted that the molecular weight distribution of dextran was narrowly dispersed.

Investigation of the cause of reduced sugar content in Kiyomi tangor fruit of Ziyang xiangcheng (Citrus junos Sieb. ex Tanaka) rootstock

Ziyang xiangcheng (Citrus junos Sieb. ex Tanaka) (Cj) rootstock is effective in Citrus production; however, when Cj rootstock was used, sugar content in Kiyomi tangor fruit was significantly lower than that in the fruit produced using Poncirus trifoliata (L.) Raf. rootstock (Pt). Therefore, using K. tangor, we explored the cause of this difference, determining sugar accumulation, sucrose-metabolism enzyme activities, and gene expression. Before ripening, sugar content in fruits with Cj rootstock was significantly lower than that in fruits with Pt rootstock, due to low fructose and sucrose content. Sucrose phosphate synthase (SPS) activity of Pt was higher than that of Cj in the early growth stage (at 90–210 days after anthesis), however it was opposite at 240–300 days after anthesis. Additionally, neutral invertase (NI) activity of Pt was higher than that of Cj. Gene expression in Pt was higher than that in Cj, but is was essentially the same at maturity. SPS and NI activities and CitSPS1 expression were positively correlated with sucrose, fructose, and glucose content, but CSCW1 expression was negatively correlated with the sugars. Overall, the weak flavour of K. tangor fruit with Cj rootstock was regulated by the sucrose metabolism-related enzymes and gene expression.

Does Sucrose Change Its Mechanism of Stabilization of Lipid Bilayers during Desiccation? Influences of Hydration and Concentration.

Sugar-membrane interactions are believed to be responsible for cell preservation during desiccation and freezing, but the molecular mechanism by which they achieve this is still not well understood. The associated decrease of the main phase transition temperature of phospholipid bilayers is explained by two opposing views on the matter: the direct sugar-phospholipid interaction at the bilayer interface (water replacement hypothesis) and an entropy-driven phase transition with sugar molecules concentrating away from the lipid interface (hydration forces explanation). Both mechanisms are supported by experiments but molecular dynamics (MD) simulations have overwhelmingly shown the occurrence of direct sugar-phospholipid interactions. We have performed MD simulations of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers at different water and sucrose contents. The behavior of sucrose was found to depend on both the sucrose and water contents: at high sucrose concentration and at low hydration, it is best described by the hydration forces explanation model, whereas at low sucrose concentration, it is consistent with the water replacement hypothesis model. These simulations reveal that at low concentration, sucrose molecules preferentially interact directly with the membrane interface while at high concentration, they preferentially accumulate in the intermembrane solution. The transition between the two modes of interaction is revealed for the first time as being governed by the saturation of the lipid bilayer interface with sucrose molecules, and this occurs more rapidly as the level of hydration decreases.

Comparative characteristics of the biochemical composition of chard and table beet accessions from VIR collection

Relevance. Healthy eating is one of the many steps that lead to a healthy nation. It implies the provision of the human body with all the necessary elements for its normal functioning. Within the framework of import substitution, it is extremely important to identify and popularize valuable crops that are suitable for cultivation in the territory of the Russian Federation. One of these rarely studied and insufficiently studied cultures is the leaf variety of beet –chard (Beta vulgaris L. ssp. сicla). Man uses in the food the fleshy petioles and leaves of this plant.Material and methods. The purpose of the research was to identify the characteristics of the biochemical composition of chard and compare them with the widespread red beet. The object of the study was 44 accessions of red beet (Beta vulgaris L. ssp. vulgaris) and 32 accessions of chard from the VIR collection, differing in phenotype and origin. The accessions were cultivated in the vegetable crop rotation in the Research and production base “Pushkin and Pavlovsk laboratories of VIR” (Pushkin, Leningrad region) for two years (2014 and 2015). Biochemical analysis was performed using standard methods. The quantitative and qualitative composition of the metabolites was assessed using GС-МS (Gas Chromatography-Mass Spectrometry).Results. The results of the study revealed significant variability of indicators depending on the specific genotype. The indicators of the content of ascorbic acid, protein and pigments: betanin in beetroot and β -carotene in leafy can be attributed to slightly varying. A detailed comparative description of the content of carbohydrate profile metabolites is given. It is shown that chard is better balanced in terms of monosaccharides content, differs in low sucrose content. The amino acid composition of chard is richer and more diverse than that of table beet, it is significantly ahead of table beet in essential amino acids for humans. Selected accessions of chard are recommended for use in infant, dietary and diabetic nutrition. Due to the high protein content (83% higher than that of red beet), the culture is recommended as an ingredient for feed production. Leaf beet has a number of valuable advantages: unpretentious in cultivation, decorative and, most importantly, has great potential for use in human nutrition and fodder production.