Effects of ascorbic acid and ascorbic acid 2-phosphate, a long-acting vitamin C derivative, on the proliferation and differentiation of human osteoblast-like cells

In order to investigate the effect of ascorbic acid (AsA) and ascorbic acid 2-phosphate (Asc 2-P), a long-acting vitamin C derivative, on the growth and differentiation of human osteoblast-like cells, we supplemented the culture medium of MG-63 cells with various concentrations (0.25 to 1 mM) of these factors. Asc 2-P significantly stimulated nascent cell growth at all concentrations in the presence of fetal bovine serum (FBS). On the other hand, AsA showed a growth repressive effect depending on its concentration, and that of FBS. Asc 2-P also increased expression of osteoblast differentiation markers, such as collagen synthesis and alkaline phosphatase (ALP) activity. These stimulative activities of Asc 2-P were attenuated by inhibitors of collagen synthesis, indicating that these effects were dependent on collagen synthesis. Electron micrographs of the cells showed the formation of a three-dimensional tissue-like structure endowed with a mature extracellular matrix in the presence of Asc 2-P.     

Effect of ascorbic, isoascorbic and dehydroascorbic acids on the growth and survival of Campylobacter jejuni

Ascorbic acid (AsA), added to nutrient broth at a concentration of 5 mmol/l, was bactericidal towards Campylobacter jejuni grown at 42°C in a micro-aerobic atmosphere. Specific enzymes, radical scavengers, metal chelators and reducing agents were tested as possible antagonists to the cytotoxicity of AsA. The addition of catalase or of the metal chelators ceruloplasmin or Desferal did not prevent the cytotoxic effect of AsA. The addition of the hydroxyl radical scavengers mannitol. formate, histidine or DMSO also failed to counteract the toxicity of AsA. On the other hand, thiourea or cysteamine and the reducing agents cysteine or dithionite significantly increased the recovery of C. jejuni in the presence of AsA. Although the possibility of the involvement of hydroxyl radicals in AsA cytotoxicity cannot be ruled out, it appears that the toxic effect of AsA is due mostly to the formation of products of oxidation of AsA and particularly to dehydroascorbic acid (DHA). Dehydroascorbic acid was also bactericidal to C. jejuni at a concentration of 5 mmol/l. Of all the compounds tested, only cysteamine was effective in preventing (partially) the toxic effect of DHA. The growth of C. jejuni was not inhibited by the addition of 5 mmol/l of isoascorbic acid or sodium isoascorbate.     

Effect of ascorbic, isoascorbic and dehydroascorbic acids on the growth and survival of Campylobacter jejuni

Ascorbic acid (AsA), added to nutrient broth at a concentration of 5 mmol/l, was bactericidal towards Campylobacter jejuni grown at 42 degrees C in a micro-aerobic atmosphere. Specific enzymes, radical scavengers, metal chelators and reducing agents were tested as possible antagonists to the cytotoxicity of AsA. The addition of catalase or of the metal chelators ceruloplasmin or Desferal did not prevent the cytotoxic effect of AsA. The addition of the hydroxyl radical scavengers mannitol, formate, histidine or DMSO also failed to counteract the toxicity of AsA. On the other hand, thiourea or cysteamine and the reducing agents cysteine or dithionite significantly increased the recovery of C. jejuni in the presence of AsA. Although the possibility of the involvement of hydroxyl radicals in AsA cytotoxicity cannot be ruled out, it appears that the toxic effect of AsA is due mostly to the formation of products of oxidation of AsA and particularly to dehydroascorbic acid (DHA). Dehydroascorbic acid was also bactericidal to C. jejuni at a concentration of 5 mmol/l. Of all the compounds tested, only cysteamine was effective in preventing (partially) the toxic effect of DHA. The growth of C. jejuni was not inhibited by the addition of 5 mmol/l of isoascorbic acid or sodium isoascorbate.     

外源抗坏血酸对镉胁迫下黑藻抗氧化系统的保护作用

研究了不同浓度抗坏血酸(ascorbic acid,AsA)对5 mg·L^-1Cd²⁺胁迫下黑藻（Hydrilla verticillata）体内超氧阴离子(O₂^-)产生速率、过氧化氢(H₂O₂)含量、抗坏血酸和谷胱甘肽(GSH)含量,以及超氧化物歧化酶(SOD)、超氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性的影响.结果表明,与单一Cd²⁺胁迫相比,随着外源AsA浓度的升高,黑藻体内活性氧生成速率逐步降低;抗氧化物质AsA先升后降,GSH缓慢升高;抗氧化酶APX和CAT活性先升后降,POD活性逐步下降,并接近正常状态,对SOD活性影响不大.可见AsA能够有效缓解Cd²⁺对黑藻的毒害,且60 mg·L^-1浓度下的缓解效果最好.     

Studies on avian erythrocyte metabolism. XVI. Accumulation of 2,3-bisphosphoglycerate with shifts in oxygen affinity of chicken erythrocytes

The ability of the chicken erythrocyte to accumulate 2,3-bisphosphoglycerate (2,3-P2-glycerate) and its effect upon the oxygen affinity (P50) of the cell suspensions have been determined. Erythrocytes from chick embryos, which contain 4-6 mM 2,3-P2-glycerate, and from chickens at various ages, which contain 3-4 mM inositol pentakisphosphate but no 2,3-P2-glycerate, were incubated with inosine, pyruvate, and inorganic phosphate. Red blood cells from 20-day chick embryos incubated in Krebs-Ringer, pH 7.45, containing 20 mM inosine and 20 mM pyruvate had an increase in 2,3-P2-glycerate from 4.3 to 11.9 mM after 4 h. Importantly, as 2,3-P2-glycerate concentration increased there was a corresponding increase in P50 of the cell suspension. Further, erythrocytes from 9- and 11-week, and 7-, 14-, 24-, and 28-month-old chickens when incubated similarly with inosine and pyruvate accumulated 2,3-P2-glycerate with corresponding increases in P50 of the cell suspensions. The ability of the red cell to accumulate this compound under the incubation conditions used apparently decreases with age of the bird (e.g., 11.9 mM in the 20-day embryo to 1.1 mM in the 28-month-old chicken after 4 h incubation). Despite the presence of significant amounts of inositol-P5, the accumulation of 2,3-P2-glycerate markedly decreases oxygen affinity of the cell suspensions. The delta P50/mumol increase in 2,3-P2-glycerate in the red cells of the 20-day chick embryo after 4 h incubation is 1.5 Torr; conversely, the delta P50/mumol decrease in 2,3-P2-glycerate in the red cells of the 17-day embryo after 6 h incubation in the presence of sodium bisulfite is 2.8 Torr. The demonstrated ability of the chicken erythrocyte to accumulate 2,3-P2-glycerate in response to certain substrates suggests that regulation of concentration of this compound could contribute significantly to regulation of blood oxygen affinity in birds.     

Effect of intermediates on ascorbic acid and oxalate biosynthesis of rice and in relation to its stress resistance.

Rice (Oryza sativa L.) roots were fed with L-ascorbic acid (AsA) and its putative precursors to observe AsA and oxalate concentrations and the resistance of rice to chilling, water stress, and Al toxicity. AsA concentration was significantly enhanced in both shoots and roots of rice seedlings by feeding with D-glucose or L-galactono-gamma-lactone. AsA or L-galactono-gamma-lactone treatment increased accumulation of oxalate mainly in soluble form, while these treatments decreased electrolyte leakage from root cells, H2O2 and lipid peroxidation level in rice seedlings subjected to chilling, water stress, and Al toxicity. They also alleviated the inhibition on root growth by Al. These results indicated that AsA and its immediate precursor protected plants against the oxidative damages induced by various stresses. However, 0.5 mM AsA and 10 mM L-galactono-gamma-lactone treatment had no significant effect on superoxide dismutase and catalase activity and ascorbate-peroxidase activities. Enhanced Al resistance caused by AsA and L-galactono-gamma-lactone may possibly be resulted from increased level of oxalate, which acts as metal chelator. Thus it is proposed that manipulation of AsA and oxalate biosynthesis through enhancement of L-galactono-gamma-lactone level in plants could be a strategy for improving abiotic stress tolerance.     

Enhancement of antioxidant enzyme activities in rice callus by ascorbic acid under salinity stress

Ascorbic acid (AsA) is naturally occurring compound with antioxidant activity and plays a pivotal role in plant cell adaptation to salinity stress. The objective of this work was to assess the influence of exogenous AsA on the embryogenic callus of indica rice (Oryza sativa L.) cv. MRQ74 cultivated under saline conditions. NaCl (200 mM) decreased callus fresh and dry masses, relative growth rate, and K⁺ and Ca⁺² content, and increased Na⁺ content and Na⁺/K⁺ ratio. Application of AsA (0.5 or 1 mM) alleviated these effects of salinity. Activities of peroxidase, catalase, superoxide dismutase, as well as content of proline increased due to the NaCl treatment, and these parameters were mostly further increased by 0.5 mM AsA. Thus, AsA can increase callus tolerance to NaCl stress.     

The decline in ascorbic acid content is associated with cadmium toxicity of rice seedlings

Cadmium (Cd) toxicity of rice (Oryza sativa L. cv. Taichung Native 1) seedlings was evaluated by the decrease in chlorophyll content and the increase in malondialdehyde (MDA) in the second leaves of rice seedlings. CdCl₂ (5 μM) treatment was accompanied by a decrease in the contents of ascorbic acid (AsA) and AsA + dehydroascorbate (DHA) and in the ratios of AsA/DHA in leaves. However, CdCl₂ treatment resulted in an increase in DHA content in leaves. Moreover, the decrease in AsA content was prior to the occurrence of chlorosis and associated with the increase in MDA content in the leaves of seedlings treated with Cd. Pretreatment with 0.5 mM AsA or l-galactono-1,4-lactone (GalL), the biosynthetic precursor of AsA, for 6 h resulted in an increase in the contents of AsA and reduced glutathione (GSH), the ratios of AsA/DHA and GSH/oxidized glutathione, and the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) in the leaves of rice seedlings. Quantitative RT-PCR was applied to quantify the mRNA levels for OsAPX and OsGR genes from rice leaves to examine the effect of AsA or GalL pretreatment on the expression of OsAPX and OsGR genes in rice leaves. The expression of OsAPX2, OsAPX3, OsAPX4, OsAPX5, OsAPX6, OsAPX7, and OsGR1 was increased by AsA or GalL pretreatment. Rice seedlings pretreated with AsA or GalL were observed to reduce the subsequent Cd-induced toxicity. Our results suggest that AsA content may play a role in regulating Cd toxicity of rice seedlings.     

Automatic fermentation control based on a real-time in situ SIRE biosensor regulated glucose feed

Monitoring and regulation of fermentations is of a paramount industrial and academic importance in order to keep conditions optimal during the entire process. Established techniques employed today include HPLC and spectrophotometry, which both have the disadvantage that broth samples have to be drawn from the fermentor and that they often require sample pre-treatment. The objectives of this study was to design and evaluate a software controlled automatic real-time SIRE biosensor connected to a glucose feed solution pump for in situ based monitoring and regulation of the glucose concentration during a yeast fermentation process. The maximal frequency for the measuring-regulation cycles was 30/h. A 10 mM mean glucose concentration level was successfully maintained within +/-0.013 mM during 60 min fermentations at various concentrations of yeast (10, 20, 40 and 80g/l). The on/off-regulator used caused some expected fluctuations (oscillations) of the glucose concentration around the mean value (+/-0.12 mM at 10 g/l, +/-0.26 mM at 20 g/l, +/-0.51 mM at 40 g/l, and +/-0.99 mM at 80 g/l). A 7-h fermentation process (10 mM glucose and 20 g/l yeast) was successfully monitored and regulated. The obtained measuring data were found to be 8.5-22.9% lower than data obtained with a commercially available spectrophotometric kit. The difference increased linearly (-0.26 mM/h), during the fermentation process and indicated that some clogging of the in situ positioned probe occurred. The speed and the automatisation adaptability of the presented device suggest advantages compared to established techniques.     

Purification and regulatory properties of pyruvate kinase from Veillonella parvula.

The nonglycolytic, anaerobic organism Veillonella parvula M4 has been shown to contain an active pyruvate kinase. The enzyme was purified 126-fold and was shown by disc-gel electrophoresis to contain only two faint contaminating bands. The purified enzyme had a pH optimum of 7.0 in the forward direction and exhibited sigmoidal kinetics at varying concentrations o-f phosphoenol pyruvate (PEP), adenosine 5'-monophosphate (AMP), and Mg-2+ ions with S0.5 values of 1.5, 2.0, and 2.4 mM, respectively. Substrate inhibition was observed above 4 m PEP. Hill plots gave slope values (n) of 4.4 (PEP), 2.8 (adenosine 5'-diphosphate), and 2.0 (Mg-2+), indicating a high degree of cooperativity. The enzyme was inhibited non-competitively by adenosine 5'-triphosphate (Ki = 3.4 mM), and this inhibition was only slightly affected by increasing concentration of Mg-2+ ions to 30 mM. Competitive inhibition was observed with 3-phosphoglycerate, malate, and 2,3-diphosphoglycerate but only at higher inhibitor concentrations. The enzyme was activated by glucose-6-phosphate (P), fructose-6-P, fructose-1,6-diphosphate (P2), dihydroxyacetone-P, and AMP; the Hill coefficients were 2.2, 1.8, 1.5, 2.1, and 2.0, respectively. The presence of each these metabolites caused substrate velocity curves to change from sigmoidal to hyperbolic curves, and each was accompanied by an increase in the maximum activity, e.g., AMP greater than fructose-1,6-P2 greater than dihydroxyacetone-P greater than glucose-6-P greater than fructose-6-P. The activation constants for fructose-1,6-P2, AMP, and glucose-6-P were 0.3, 1.1, and 5.3 mM, respectively. The effect of 5 mM fructose-1,6-P2 was significantly different from the other compounds in that this metabolite was inhibitory between 1.2 and 3 mM PEP. Above this concentration, fructose-1,6-P2 activated the enzyme and abolished substrate inhibition by PEP. The enzyme was not affected by glucose, glyceraldehyde-3-P, 2-phosphoglycerate, lactate, malate, fumerate, succinate, and cyclic AMP. The results suggest that the pyruvate kinase from V. parvula M4 plays a central role in the control of gluconeogenesis in this organism by regulating the concentration of PEP.     

Fructose effect to suppress hepatic glycogen degradation

The effect of fructose on glycogen degradation was examined by measuring the flux of 14C from prelabeled glycogen in perfused rat livers. During 2-h refeeding of 24-h-fasted rats, newly synthesized hepatic glycogen was labeled by intraperitoneal injection of [U-14C] galactose (0.1 mg and 0.02 microCi/g of body weight). The livers of refed rats were then perfused in a nonrecirculating fashion for an initial 30 min with glucose alone (10 mM) for the following 60 min with glucose (10 mM) without (n = 5) or with fructose (1, 2, or 10 mM; n = 5 for each). When livers were exposed to fructose, release of label into the perfusate immediately declined and remained markedly suppressed through the end of perfusion (p less than 0.05). The suppression was dose-dependent; at steady state (50-70 min), label release was suppressed 45, 64, and 72% by 1, 2, and 10 mM fructose, respectively (p less than 0.0001). Suppression was not accompanied by significant changes in the activities of glycogen synthase or phosphorylase assessed in vitro. These results suggest the existence of allosteric inhibition of phosphorylase in the presence of fructose. Fructose 1-phosphate (Fru-1-P) accumulated in proportion to fructose (0.11 +/- 0.01 without fructose, 0.86 +/- 0.03, 1.81 +/- 0.18, and 8.23 +/- 0.60 mumol/g of liver with 1, 2, and 10 mM fructose, respectively; p less than 0.0001). Maximum inhibition of label release was 82%; the Fru-1-P concentration for half inhibition was 0.57 mumol/g of liver, well within the concentration of Fru-1-P attained during refeeding. We conclude that fructose enhances net glycogen accumulation in liver by suppressing glycogenolysis and that the suppression is presumably caused by allosteric inhibition of phosphorylase by Fru-1-P.     

Oxidative inactivation of an extramitochondrial acetyl-CoA hydrolase by autoxidation of L-ascorbic acid

The activity of acetyl-CoA hydrolase (dimeric form) purified from the supernatant fraction of rat liver was shown to have a half-life (t1/2) of 3 min at 0 degree C, but to stable at 37 degrees C (t1/2 = 34 h) [Isohashi, F., Nakanishi, Y. & Sakamoto, Y. (1983) Biochemistry 22, 584-590]. Incubation of the purified enzyme with L-ascorbic acid (AsA) at 37 degrees C resulted in inactivation of the enzyme (t1/2 = 90 min at 2 mM AsA). The extent of inactivation was greatly enhanced by addition of transition metal ions (Cu2+, Fe2+, and Fe3+). Thiol reducing agents, such as reduced glutathione and DL-dithiothreitol, protected the hydrolase from inactivation by AsA. However, these materials did not restore the catalytic activity of the enzyme inactivated by AsA. When AsA solution containing Cu2+ was preincubated under aerobic conditions at 37 degrees C for various times in the absence of enzyme, and then aliquots were incubated with the enzyme solution for 20 min, remaining activity was found to decrease with increase in the preincubation time, reaching a minimum at 60 min. However, further preincubation reduced the potential for inactivation. Catalase, a hydrogen peroxide (H2O2) scavenger, almost completely prevented inactivation of the enzyme by AsA plus Cu2+. Superoxide dismutase and tiron, which are both superoxide (O2-) scavengers, also prevented inactivation of the enzyme. A high concentration of mannitol, a hydroxyl radical (OH) scavenger, partially protected the enzyme from inactivation. These results suggest that inactivation of the enzyme by AsA in the presence of Cu2+ was due to the effect of active oxygen species (H2O2, O2-, OH) that are known to be autoxidation products of AsA. Valeryl-CoA, a competitive inhibitor of acetyl-CoA hydrolase, greatly protected the enzyme from inactivation by AsA plus Cu2+, but ATP and ADP, which are both effectors of this enzyme, had only slight protective effects. These results suggest that inactivation of this enzyme by addition of AsA plus Cu2+ was mainly due to attack on its active site.     

Improved ethanol production from xylose with glucose isomerase and Saccharomyces cerevisiae using the respiratory inhibitor azide

Summary Ethanol was produced from xylose, using the enzyme glucose isomerase (xylose isomerase) and Saccharomyces cerevisiae. The influence of aeration, pH, enzyme concentration, cell mass and the concentration of the respiratory inhibitor sodium azide on the production of ethanol and the formation of by-products was investigated. Anaerobic conditions at pH 6.0, 10 g/l enzyme, 75 g/l dry weight cell mass and 4.6 mM sodium azide were found to be optimal. Under these conditions theoretical yields of ethanol were obtained from 42 g/l xylose within 24 hours.In a fed-batch culture, 62 g/l ethanol was produced from 127 g/l xylose with a yield of 0.49 and a productivity of 1.35 g/l·h.     

Growth and butyric acid production by Clostridium populeti

The growth of Clostridium populeti in 2% (w/v) glucose medium containing 0.2% (w/v) yeast extract was optimal with 10 mM NH₄Cl as the nitrogen source. Although the maximum specific growth rate (=0.32 h^-1) with 5 mM NH₄Cl was similar, the biomass yield was about 30% lower than that at the optimum. Either sodium sulphide or cysteine-HCl at an optimum concentration of 0.33 mM and 5.0 mM respectively, could serve as the sole sulphur source for growth. The growth rate was unaffected by initial glucose concentrations of up to 10% (w/v), but in the presence of 15% glucose it declined by about 35%. The molar yield of butyric acid (mol/mol glucose) declined from 0.70 in 1% (w/v) initial glucose medium to 0.39 in 10% glucose medium. In 5.7% initial glucose medium, butyric acid levels of 6.3 g/l were obtained (0.56 mol butyrate/mol glucose) after 72 h of incubation in 2.5 l batch cultures. A decrease of about 50% in the maximum specific growth rate of C. populeti was observed in the presence of an initial concentration of either 1.2 g/l of butyric acid or 18.9 g/l of acetic acid.This paper is issued as NRCC No. 29032     

Process development and optimisation of lactic acid purification using electrodialysis

Cell free sodium lactate solutions were subjected to purification based on mono- and bi-polar electrodialysis. Lactate concentration in the product stream increased to a maximum of 15% during mono-polar electrodialysis. Stack energy consumption averaged 0.6 kW h kg(-1) lactate transported at current efficiencies in the 90% range. Under optimum feed concentration (125 g l(-1)) and process conditions (auto-current mode with conductivity setpoints of minimum 5 and maximum 40 mS cm(-1)), lactate flux reached 300 g m(-2) h(-1) and water flux were low for mono-polar electrodialysis averaging 0.3 kg H(2)O per M lactate transported. Glucose in the concentrate stream solutions was reduced to < 2 g l(-1). Acetate impurities enriched from about 0.5 g l(-1) in the feed stream to 1.5 g l(-1) in the concentrate stream solutions. After mono-polar electrodialysis, the concentrated sodium lactate solutions were further purified using bi-polar electrodialysis. Water transport during bi-polar electrodialysis reached figures of 0.070 - 0.222 kg H(2)O per M lactate. Free lactic acid concentration reached 16% with lactate flux of up to 300 g m(-2) h(-1). Stack energy consumption ranged from 0.6 to 1 kW h per kg lactate. Under optimised process conditions current efficiency during bi-polar electrodialysis was consistently around 90%. Glucose was further reduced from 2 to <1 g l(-1) in the free lactic acid solution. Acetic acid impurity remained at around 1 g l(-1). Significant reduction in colour and minerals in the product streams was observed during electrodialysis purification.     

Optimization of production and reaction conditions of polygalacturonase from Byssochlamys fulva

In the present study, the optimization of production and reaction conditions of polygalacturonase produced by a fungus Byssochlamys fulva MTCC 505 was achieved. The production of polygalacturonase with a considerable activity of 1.28 IU/ml was found when the culture was shaken at 30°C for 5 days in 100 ml of medium containing (w/v) 10 g/l pectin, 2 g/l NaNO?, 1 g/l KH?PO?, 0.5 g/l KCl, 0.5 g/l MgSO?. 7H?O, 0.001 g/l FeSO?. 7H?O, 0.001 g/l CaCl?. The best carbon and nitrogen source for this enzyme were pectin (1%) and Ca(NO?)? (0.1%), respectively. The enzyme gave maximum activity at incubation time of 72 h, temperature of 30°C and pH 4.5. During the optimization of reaction conditions, the enzyme showed maximum activity in sodium citrate buffer (50 mM) of pH 5.5 at 50°C reaction temperature for 15 minutes of incubation. The enzyme showed greater affinity for polygalacturonic acid as substrate (0.5%). Km and Vmax values were 0.15 mg/ml and 4.58 μmol/ml/min. The effect of various phenolics, thiols, protein inhibitors and metal ions on the enzyme activity was investigated. The enzyme was quite stable at 4°C and 30°C. At 40°C the half life of the enzyme was 6 h and at 60°C it was 2 h.     

Linking ascorbic acid production in Ribes nigrum with fruit development and changes in sources and sinks

Background and Aims

Understanding the synthesis of ascorbic acid (l-AsA) in green tissues in model species has advanced considerably; here we focus on its production and accumulation in fruit. In particular, our aim is to understand the links between organs which may be sources of l-AsA (leaves) and those which accumulate it (fruits). The work presented here tests the idea that changes in leaf and fruit number influence the accumulation of l-AsA. The aim was to understand the importance of leaf tissue in the production of l-AsA and to determine how this might provide routes for the manipulation of fruit tissue l-AsA.

Methods

The experiments used Ribes nigrum (blackcurrant), predominantly in field experiments, where the source–sink relationship was manipulated to alter potential leaf l-AsA production and fruit growth and accumulation of l-AsA. These manipulations included reductions in reproductive capacity, by raceme removal, and the availability of assimilates by leaf removal and branch phloem girdling. Natural variation in fruit growth and fruit abscission is also described as this influences subsequent experimental design and the interpretation of l-AsA data.

Key Results

Results show that fruit l-AsA concentration is conserved but total yield of l-AsA per plant is dependent on a number of innate factors many of which relate to raceme attributes. Leaf removal and phloem girdling reduced fruit weight, and a combination of both reduced fruit yields further. It appears that around 50 % of assimilates utilized for fruit growth came from apical leaves, while between 20 and 30 % came from raceme leaves, with the remainder from ‘storage’.

Conclusions

Despite being able to manipulate leaf area and therefore assimilate availability and stored carbohydrates, along with fruit yields, rarely were effects on fruit l-AsA concentration seen, indicating fruit l-AsA production in Ribes was not directly coupled to assimilate supply. There was no supporting evidence that l-AsA production occurred predominantly in green leaf tissue followed by its transfer to developing fruits. It is concluded that l-AsA production occurs predominantly in the fruit of Ribes nigrum.     

Production of high-content fructo-oligosaccharides by an enzymatic system from Penicillium rugulosum

Summary The production of high-content fructo-oligosaccharides from sucrose by a crude FTF from a new strain of Penicillium isolated in our Laboratory was investigated. The optimum conditions for the production of the enzyme and for the enzymic reaction have been determined. It has been demonstrated that the crude enzyme acts as a mixed enzyme system of fructosyl transferase (FTF; Class 2 of Enzyme Nomenclature) and glycosidases (Class 3 of Enyme Nomenclature). Under optimum conditions: pH 5.5, temperature 55°C, sucrose concentration 750 g/l, enzyme concentration 5 FTF units/g sucrose, conversion yield up to 80% were obtained and high concentration of nystose (412 g/l) and fructofuranosyl-nystose (176 g/l) were accumulated.