Intracellular Changes in Ions and Organic Solutes in Halotolerant Brevibacterium sp. Strain JCM 6894 after Exposure to Hyperosmotic Shock

In the present study we aimed to observe the intracellular responses when there was a hyperosmotic shock with a large shift in ionic strength in nutrient-rich and nutrient-poor external environments in order to clarify the availability of substrates. To do this, we used the halotolerant organism Brevibacterium sp. strain JCM 6894, which is able to grow in the presence of a wide range of salt concentrations. Hyperosmotic shock was induced by transferring cells in the late exponential phase of growth in a complex medium containing 0.5 M NaCl into either old or fresh culture medium containing 2 M NaCl. Changes in the growth rate, in the pH of the medium, and in the internal cation or organic solute concentrations in the cytosol after an upshock were analyzed as a function of incubation time. The cells exhibited very different responses to upshocks in fresh culture medium and in old culture medium; in fresh culture medium, growth was stimulated and the medium became more acidic, whereas the old culture medium repressed growth and the medium became more alkaline. The intracellular free Na⁺ concentrations remained low (80 nmol mg of protein⁻¹) after an upshock in fresh culture medium, although they quickly increased twofold in the old culture medium. In contrast, K⁺ ions immediately accumulated in the cells in fresh culture medium, whereas K⁺ ions were taken up quite slowly in old culture medium. Furthermore, the cells placed in fresh culture medium transiently accumulated alanine and glutamine in response to the upshock, but the cells placed in old culture medium did not. Growth of the Brevibacterium strain at higher levels of salinity was supported by ectoine synthesis but was not observed after the shift to high-osmolarity conditions in the old culture. In the fresh culture, however, ectoine was vigorously synthesized in cells for more than 5 h after the upshock; the concentration of ectoine in cells was more than 3,500 nmol mg of protein⁻¹ at 10 h, which corresponded to a ninefold increase compared to the concentration before the shock. These findings are consistent with the results of an analysis of the extracellular medium composition before and after the upshock.     

Screening Wheat Genotypes for High Callus Induction and Regeneration Capability from Immature Embryo Cultures

Selecting the explant genotypes is crucial step in in vitro culture and Agrobacterium-mediated transformation system due to its host range specificity. Immature embryos of five winter and three spring wheat (Triticum aestivum L) cultivars were evaluated for tissue culture response in three callus initiation media. MS medium containing 2,4-0 (2 mg ml^-1) plus B5 vitamins (MSB5), MS medium containing 2,4-0 (1 mg ml^-1) with no vitamins (MS1GC) or MS medium containing picloram (2.2 mg ml^-1) and 2,4-0 (0.5 mg ml^-1) plus MS vitamins (CM4C) were used for callus initiation. Percentage of callus induction varied widely with the genotype and initiation medium used, with values ranging from 5.7% to 100%. Embryogenic capacity of genotypes was evaluated by number of somatic embryos formed from cultured immature embryos. Bob White (spring) and NE92458 (winter) were equal and most embryogenic; Pronghorn and 2137 (both winter) were the poorest. CM4C medium was found to be the best medium for initiating embryogenic callus among three culture media tested. A standard regeneration procedure was used. The genotypes with the highest regeneration efficiencies were Bob White, Fielder and NE92458, (1.8, 1.4 and 1.6 plantslexplant, respectively).     

Changes in growth and size of Keratella cochlearis (Gosse) in relation to some environmental factors in cultures

Keratella cochlearis (Gosse) was cultured non-axenically in Carefoot medium diluted with Erken water at 5 °C, 15 °C and 20 °C with Rhodomonas minuta (Skuja) as a food alga. The rotifer reached ca. 120 ind. ml^?1, having generation times of 2–7 days, a Q₁₀-value of ca. 2, and at the lowest temperature >20% longer posterior spines. When co-cultured with Chlorella sp., at 0–30 mg Ca l^?1 and 1.6 meq NaHCO₃ l^?1 in medium L 11 at 20 °C, the maximum generation time and individual numbers were 3–4 days and up to 100 ind. ml^?1, respectively. Animal numbers increased in relation to nutrient multiples, up to two multiples, of the culture medium L 16. Growth and length were reduced, although the width increased above two multiples of this culture medium. The trace metal tolerance was broad and increased additions of a metal mixture (L 11) slightly increased the length of the rotifers. No major changes in the length were observed when HCO₃ or Ca were varied in the culture medium (L 11), although a decrease in the length was noted in old cultures.     

Galanthamine production in “shoot-clump” cultures of Narcissus confusus in liquid-shake medium

Galanthamine (GAL) is increasingly used in the treatment of Alzheimer's disease. We have attempted to develop a method of producing this alkaloid using in vitro cultures of Narcissus confusus plants. The “shoot-clump” culture in liquid medium was shown to be an appropriate method for the micropropagation of this bulbous plant. The complete process included three steps:

1. culture of “twin-scales” starting from the bulbs;
2. culture of the newly formed shoots in a medium for bud proliferation (Murashige Skoog+1 mg l^-1 of 2,4-dichlorophenoxyacetic acid+5 mg l^-1 of benzyladenine), and
3. culture of “shoot-clumps” in a liquid-shake medium. Here we describe the effect of the addition of trans-cinnamic acid, a precursor in the biosynthesis of the Amaryllidaceae alkaloids, on the production of galanthamine and related alkaloids, and also on the growth of the “shoot-clump” culture. The production of galanthamine was found to be inhibited by the addition of the precursor, which promoted the production of the other alkaloid in the same biosynthetic pathway, N-formyl-norgalanthamine. The total production of galanthamine in the control cultures in day-long photoperiod was 2.50 mg per culture, of which 1.97 mg per culture were released into the medium.

     

Effects of thidiazuron and N6-benzylaminopurine on shoot regeneration of Phalaenopsis

Adventitious bud formation from the vegetative buds of the flower stalks of Phalaenopsis occurred on Vacin and Went medium with 15% coconut water and 5 to 40 μM thidiazuron (TDZ) or 40 μM N⁶-benzylaminopurine. The highest efficiency of induction was achieved with 5 or 10 μM TDZ. Adventitious buds developed into shoots on VWC medium. TDZ was more effective than BAP in stimulating the axillary buds of intact shoots to develop. Regenerated shoots rooted after about two months of culture on VWC medium with 1% sucrose. Shoot tips excised from the regenerated shoots initiated protocorm-like bodies after two months of culture on VWC medium.     

Very Low Ethanol Concentrations Affect the Viability and Growth Recovery in Post-Stationary-Phase Staphylococcus aureus Populations

Pharmaceuticals, culture media used for in vitro diagnostics and research, human body fluids, and environments can retain very low ethanol concentrations (VLEC) (≤0.1%, vol/vol). In contrast to the well-established effects of elevated ethanol concentrations on bacteria, little is known about the consequences of exposure to VLEC. We supplemented growth media for Staphylococcus aureus strain DSM20231 with VLEC (VLEC⁺ conditions) and determined ultramorphology, growth, and viability compared to those with unsupplemented media (VLEC⁻ conditions) for prolonged culture times (up to 8 days). VLEC⁺-grown late-stationary-phase S. aureus displayed extensive alterations of cell integrity as shown by scanning electron microscopy. Surprisingly, while ethanol in the medium was completely metabolized during exponential phase, a profound delay of S. aureus post-stationary-phase recovery (>48 h) was observed. Concomitantly, under VLEC⁺ conditions, the concentration of acetate in the culture medium remained elevated while that of ammonia was reduced, contributing to an acidic culture medium and suggesting decreased amino acid catabolism. Interestingly, amino acid depletion was not uniformly affected: under VLEC⁺ conditions, glutamic acid, ornithine, and proline remained in the culture medium while the uptake of other amino acids was not affected. Supplementation with arginine, but not with other amino acids, was able to restore post-stationary-phase growth and viability. Taken together, these data demonstrate that VLEC have profound effects on the recovery of S. aureus even after ethanol depletion and delay the transition from primary to secondary metabolite catabolism. These data also suggest that the concentration of ethanol needed for bacteriostatic control of S. aureus is lower than that previously reported.     

Uptake of CeO2 Nanoparticles and Its Effect on Growth of Medicago arborea In Vitro Plantlets

The present study analyzes some effects of nano-CeO₂ particles on the growth of in vitro plantlets of Medicago arborea when the nanoceria was added to the culture medium. Various concentrations of nano-CeO₂ and bulk ceric oxide particles in suspension form were introduced to the agar culture medium to compare the effects of nanoceria versus ceric oxide bulk material. Germination rate and shoot dry weight were not affected by the addition of ceric oxide to the culture media. Furthermore, no effects were observed on chlorophyll content (single-photon avalanche diode (SPAD) measurements) due to the presence of either nano- or micro-CeO₂ in the culture medium. When low concentrations of nanoceria were added to the medium, the number of trifoliate leaves and the root length increased but the root dry weight decreased. Also the values of maximum photochemical efficiency of PSII (F _v/F _m) showed a significant decrease. Dark-adapted minimum fluorescence (F ₀) significantly increased in the presence of 200 mg L^?1 nanoceria and 400 mg L^?1 bulk material. Root tissues were more sensitive to nanoceria than were the shoots at lower concentrations of nanoceria. A stress effect was observed on M. arborea plantlets due to cerium uptake.     

Optimization of culture medium for microsclerotia production by Nomuraea rileyi and analysis of their viability for use as a mycoinsecticide

Microsclerotia (MS) formation was successfully induced in Nomuraea rileyi (Ascomycetes: Hypocreales) in liquid amended medium (AM) culture. To improve MS production, the culture medium was varied. Three quantitative variables, carbon, nitrogen, and basal salt sources, were investigated using the AM. An orthogonal experiment [L₉ (3)³] design was applied to optimize the culture medium. Maximum MS production (21.9 × 10⁴ MS ml^?1) was obtained using the optimized culture medium (32.0 g l^?1 of glucose, 2.0 g l^?1 of ammonium citrate, and 0.15 g l^?1 of ferrous sulfate). Subsequently, viability, including thermotolerance, shelf-life, and infection, were investigated to evaluate the potential of MS for use as a mycoinsecticide. The MS, collected from the optimized culture medium, exhibited virulence and greater thermotolerance than conidia, and maintained 86.4 % germinability after one-year room temperature storage. These results suggested that the MS obtained through optimization production can be used as a mycoinsecticide.     

Extracellular proteinase fromLactobacillus murinus

Lactobacillus murinus CNRZ 313 produced an extracellular proteinase irrespective of the Ca²⁺ content in the culture medium. Proteinase activity was optimal at 37 °C and pH 7.5 in phosphate buffer (0.2 mol/L). It was stimulated by Mg²⁺ and Mn²⁺ and was inhibited by Zn²⁺. Ca²⁺ did not affect the enzymic activity but the proteinase liberated in the presence of this ion is more stable. The enzyme was purified to homogeneity from cell-free culture medium.     

Overproduction of poly(β-malic acid) (PMA) from glucose by a novel Aureobasidium sp. P6 strain isolated from mangrove system

After over 100 strains of Aureobasidium spp isolated from mangrove system were screened for their ability to produce poly(β-malic acid) (PMA), it was found that Aureobasidium sp. P6 strain among them could produce high level of Ca²⁺-PMA. Fourteen percent glucose and 6.5 % CaCO₃ in the medium were the most suitable for Ca²⁺-PMA production. Then, 100.7 g/l of Ca²⁺-PMA was produced using Aureobasidium sp. P6 strain within 168 h at flask level. During 10-l batch fermentation, when the medium contained 12.0 % glucose, 98.7 g/l of Ca²⁺-PMA in the culture and 14.7 g/l of cell dry weight were obtained within 156 h, leaving 0.34 % reducing sugar in the fermented medium. When glucose concentration in the fermentation medium was 14.0 %, 118.3 g/l of Ca²⁺-PMA in the culture and 16.4 g/l of cell dry weight were obtained within 168 h, leaving 0.4 % reducing sugar in the fermented medium. After purification of Ca²⁺-PMA from the culture and acid hydrolysis of the pure Ca²⁺-PMA, analysis of HPLC showed that Aureobasidium sp. P6 strain only produced two main components of Ca²⁺-PMA and minor amount of calcium malate and that the hydrolysate of PMA was mainly composed of calcium malate. This is the first time to report that the novel yeast strain Aureobasidium sp. P6 strain isolated from the mangrove systems can produce such high amount of Ca²⁺-PMA.     

Influence of Environmental Factors and Medium Composition on Vibrio gazogenes Growth and Prodigiosin Production

Vibrio gazogenes ATCC 29988 growth and prodigiosin synthesis were studied in batch culture on complex and defined media and in chemostat cultures on defined medium. In batch culture on complex medium, a maximum growth rate of 0.75 h⁻¹ and a maximum prodigiosin concentration of 80 ng of prodigiosin · mg of cell protein⁻¹ were observed. In batch culture on defined medium, maximum growth rates were lower (maximum growth rate, 0.40 h⁻¹), and maximum prodigiosin concentrations were higher (1,500 ng · mg of protein⁻¹). In batch culture on either complex or defined medium, growth was characterized by a period of logarithmic growth followed by a period of linear growth; on either medium, prodigiosin biosynthesis was maximum during linear growth. In batch culture on defined medium, the initial concentration of glucose optimal for growth and pigment production was 3.0%; higher levels of glucose suppressed synthesis of the pigment. V. gazogenes had an absolute requirement for Na⁺; optimal growth occurred in the presence of 100 mM NaCl. Increases in the concentration of Na⁺ up to 600 mM resulted in further increases in the concentration of pigment in the broth. Prodigiosin was synthesized at a maximum level in the presence of inorganic phosphate concentrations suboptimal for growth. Concentrations of KH₂PO₄ above 0.4 mM caused decreased pigment synthesis, whereas maximum cell growth occurred at 1.0 mM. Optimal growth and pigment production occurred in the presence of 8 to 16 mg of ferric ion · liter⁻¹, with higher concentrations proving inhibitory to both growth and pigment production. Both growth and pigment production were found to decrease with increased concentrations of p-aminobenzoic acid. The highest specific concentration of prodigiosin (3,480 ng · mg protein⁻¹) was observed in chemostat cultures at a dilution rate of 0.057 h⁻¹. The specific rate of prodigiosin production at this dilution rate was approximately 80% greater than that observed in batch culture on defined medium. At dilution rates greater than 0.057 h⁻¹, the concentration of cells decreased with increasing dilution rate, resulting in a profile comparable to that expected for linear growth kinetics. No explanation could be found for the linear growth profiles obtained for both batch and chemostat cultures.     

Micropropagation of Cymbidium sinense using continuous and temporary airlift bioreactor systems

Airlift bioreactors were programmed for continuous and temporary immersion culture to investigate factors that affect the rhizome proliferation, shoot formation, and plantlet regeneration of Cymbidium sinense. During rhizome proliferation, the continuous immersion bioreactor system was used to explore the effects of activated charcoal (AC) in the culture medium, inoculation density, and air volume on rhizome differentiation and growth. The optimum conditions for obtaining massive health rhizomes were 0.3 g l^?1 AC in the culture medium, 7.5 g l^?1 inoculation density, and 150 ml min^?1 air. In addition, the temporary immersion bioreactor system was used for both shoot formation and plantlet regeneration. Supplementing 4 mg l^?1 6-benzylaminopurine and 0.2 mg l^?1 naphthalene acetic acid (NAA) to the culture medium promoted shoot induction from the rhizome. Cutting the rhizome explants into 1 cm segments was better for massive shoot formation than cutting into 0.25 and 0.5 cm explant segments. NAA promoted plantlet regeneration and the rooting rate (94.7 %), with whole plantlets growing well in culture medium containing 1.0 mg l^?1 NAA. Therefore, applying bioreactors in C. sinense micropropagation is an efficient way for scaling up the production of propagules and whole plantlets for the industrial production of high-quality seedlings.     

In Vitro Regenerative Competence of Cleisostoma racimeferum (Orchidaceae) Aerial Roots

Regeneration competence of aerial roots of Cleisostoma raeimeferum (Orchidaceae) from in vivo and in vitro sources was tested. The protocorm-Iike bodies and shoot buds were obtained from 2 w old in vivo grown aerial roots and 20 wold in vitro grown roots on Murashige and Skoog medium containing sucrose (3%) (w/v), casein-hydrolysate (2 g l^?1), coconut water (15%) (v/v), citric acid (200 mg l^?1) and different plant growth regulators. The morphogenetic response from in vivo grown roots was poor and only 20% of the cultures yielded protocorm-like bodies and shoot buds on medium containing IAA (2 µM) and kinetin (2 µM) in combination after 75 d of culture. While 100% morphogenetic response was exhibited by in vitro grown roots on MS medium enriched with IAA (1 µM) and kinetin (1 µM) in combination only after 25 d of culture initiation. The response initiated at the cut ends of the roots and subsequently the entire root length was taken over. Both IAA and kinetin singly stimulated mostly callusing of the explants. The rooted plantlets and multiple shoot buds were obtained after 30 d of culture from protocorm-like bodies and shoot buds on basal medium enriched with IAA (2 µM) and kinetin (6 µM) in combination. The well developed rooted plants could be obtained for transferring to potting mix after ～24 w of culture initiation.     

Author index for volume 93

The presence of Ca²⁺ is essential for survival in culture of fully grown oocytes isolated from mouse ovaries but not for survival of small, meiotically incompetent oocytes, metaphase II oocytes, and early embryos. Ninety percent of fully grown ovarian oocytes die within 2 hr when cultured in calcium-free medium (CFM). CFM death does not occur if other cations (1 mM La³⁺ or 10 mM Sr²⁺, but not 12 mM Mg²⁺ nor 1 mM D-600) replace Ca²⁺ in the medium. Sensitivity to CFM is progressively acquired by the oocyte during the growth phase, in parallel with the acquisition of meiotic competence, and is lost after 2 hr of culture in the presence of at least 0.5 mM Ca²⁺. The loss of sensitivity to CFM during in vitro culture is not related to the concomitant spontaneous resumption of meiosis, since the oocyte becomes resistant to CFM even if germinal vesicle breakdown is prevented by the addition of dibutyryl cAMP to the culture medium. Some hypotheses are put forward to explain the peculiar and transient high calcium requirements of fully grown oocytes.     

Optimization and quality assessment of adventitious roots culture in Panax quinquefolium L.

In this study, adventitious roots of Panax quinquefolium L. have been successfully established. The highest induction rate of roots was obtained in MS medium containing 3 mg L^?1 IBA after 4 weeks of culture. The culture conditions of adventitious root were optimized and evaluated with response surface methodology. The best culture conditions for root growth seemed to be 0.75 salt strength MS medium, 4.70 g L^?1 inoculum size and 40 days of culture. The active component contents of adventitious roots were compared with those of native roots. The total saponins content was found to be 16.28 mg g^?1 in native root and 4.64 mg g^?1 in adventitious root. The polysaccharide content of the adventitious root was 1.5 times higher than that in the native P. quinquefolium (30.54 vs. 20.28 mg g^?1).     

Maintenance and Neuronal Cell Differentiation of Neural Stem Cells C17.2 Correlated to Medium Availability Sets Design Criteria in Microfluidic Systems

Background

Neural stem cells (NSCs) play an important role in developing potential cell-based therapeutics for neurodegenerative disease. Microfluidics has proven a powerful tool in mechanistic studies of NSC differentiation. However, NSCs are prone to differentiate when the nutrients are limited, which occurs unfavorable by fast medium consumption in miniaturized culture environment. For mechanistic studies of NSCs in microfluidics, it is vital that neuronal cell differentiation is triggered by controlled factors only. Thus, we studied the correlation between available cell medium and spontaneous neuronal cell differentiation of C17.2 NSCs in standard culture medium, and proposed the necessary microfluidic design criteria to prevent undesirable cell phenotype changes.

Methodology/Principal Findings

A series of microchannels with specific geometric parameters were designed to provide different amount of medium to the cells over time. A medium factor (MF, defined as the volume of stem cell culture medium divided by total number of cells at seeding and number of hours between medium replacement) successfully correlated the amount of medium available to each cell averaged over time to neuronal cell differentiation. MF smaller than 8.3×10⁴ µm³/cell⋅hour produced significant neuronal cell differentiation marked by cell morphological change and significantly more cells with positive β-tubulin-III and MAP2 staining than the control. When MF was equal or greater than 8.3×10⁴ µm³/cell⋅hour, minimal spontaneous neuronal cell differentiation happened relative to the control. MF had minimal relation with the average neurite length.

Significance

MFs can be controlled easily to maintain the stem cell status of C17.2 NSCs or to induce spontaneous neuronal cell differentiation in standard stem cell culture medium. This finding is useful in designing microfluidic culture platforms for controllable NSC maintenance and differentiation. This study also offers insight about consumption rate of serum molecules involved in maintaining the stemness of NSCs.     

<Emphasis Type="Italic">Cytisus aeolicus</Emphasis> Guss. ex Lindl. <Emphasis Type="Italic">in vitro</Emphasis> cultures and genistin production

Cytisus aeolicus Guss. ex Lindl. (Fabaceae family, subfamily Faboideae) is an endangered endemic species of the Aeolian Islands, Sicily. In vitro multiplication of C. aeolicus shoots was described in this work and cell cultures were established from cotyledons and hypocotyls to investigate their potential production of isoflavones. Aseptically germinated seeds, cultivated on LS modified basal medium, gave the initial explants used both to induce axillary propagation and callus cultures. The LS (Linsmaier and Skoog) basal medium, supplemented with 0.1 mg L^?1 of 6-benzylaminopurine were used to induce axillary propagation. The callus induction was performed using the basal medium added with 5 mg L^?1 2,4-dichlorophenoxy acetic acid and 5 mg L^?1 kinetin (control medium). Basal medium was also added with 2000 mg L^?1 casein hydrolysate (CH) or 900 mg L^?1myo-inositol (MI). C. aeolicus callus cultures on CH and MI media produced an unique compound, the isoflavone genistein 7-O-ß-D-glucopyranoside (genistin), which has not previously been isolated from wild plants. Callus cultures grown on the medium containing myo-inositol produced the greatest amount of genistin. C. aeolicus tissue culture procedures could provide suitable plant material both for germplasm preservation (by micropropagation) and for biotechnological selective isoflavone production (by callus culture).     

Effect of Fermentation Conditions on Growth of Streptococcus cremoris AM2 and Leuconostoc lactis CNRZ 1091 in Pure and Mixed Cultures

Two strains of mesophilic lactic acid bacteria, Streptococcus cremoris AM2 and Leuconostoc lactis CNRZ 1091, were grown in pure and mixed cultures in the presence or absence of citrate (15 mM) and at controlled (pH 6.5) or uncontrolled pH. Microbial cell densities at the end of growth, maximum growth rates, the pH decrease of the medium resulting from growth, and the corresponding acidification rates were determined to establish comparisons. The control of pH in pure cultures had no effect on L. lactis CNRZ 1091 populations. The final populations of S. cremoris AM2, however, were at least five times higher than when the pH was not controlled (4 × 10⁸ vs. 2 × 10⁹ CFU · ml⁻¹). The pH had no effect on the growth rate of either strain. That of S. cremoris AM2 (0.8 h⁻¹) was about twice that of L. lactis CNRZ 1091. When the pH fell below 5, the growth of both strains decreased or stopped altogether. Citrate had no effect on S. cremoris AM2, while final populations of L. lactis CNRZ 1091 were two to three times higher (3 × 10⁸ CFU · ml⁻¹); it had no effect on the maximum growth rates of the two strains. Citrate attenuated the pH decrease of the medium and reduced the maximum acidification rate of the culture by 50%, due to the growth of S. cremoris AM2. Acidification due to L. lactis CNRZ 1091, however, was very slight. Regardless of the conditions of pH and citrate, the total bacterial population in mixed culture was lower (by 39%) than that of the sum of each pure culture. Mixed culture improved the maximum growth rate of L. lactis CNRZ 1091 (0.6 h⁻¹) by 50%, while that of S. cremoris AM2 was unaffected. The acidification rate of the growth medium in mixed culture, affected by the presence of citrate, resulted from the development and activity of S. cremoris AM2.     

Effects of calcitonin and parathyroid hormone on the metabolism of chondrocytes in culture

Rabbit articular chondrocytes in suspension culture synthesize Type II colagen [3α₁(II)] in the absence of extracellular Ca²⁺ and Type Icollagen [2α₁?(I)·α₂] in the complete medium. As a result of pre-treatment in monolayer culture with calcitonin or parathyroid hormone in the complete medium, an influx of Ca²⁺ into the cells occurs. These cells produce mainly Type I collagen when transferred to suspension cultures in the medium devoid of CaCl₂. If added directly to the suspension culture medium containing no CaCl₂, calcitonin stimulates an active efflux of Ca²⁺ from the cells into the medium and leads the cells to synthesize Type I collagen. Under similar conditions, parathyroid hormone does not change the collagen-phenotype.     

Effect of mixed carbon substrate on exopolysaccharide production of cyanobacterium Nostoc flagelliforme in mixotrophic cultures

The effects of organic carbon sources on cell growth and exopolysaccharide (EPS) production of dissociated Nostoc flagelliforme cells under mixotrophic batch culture were investigated. After 7?days of cultivation, glycerol, acetate, sucrose, and glucose increased the final cell density and final EPS concentrations, and mixotrophic growth achieved higher biomass concentrations. The increase in cell growth was particularly high when glucose was added as the sole carbon source. On the other hand, EPS production per dry cell weight was significantly enhanced by adding acetate. For more effective EPS production, the effects of the mixture of glucose and acetate were investigated. Increasing the ratio of glucose to acetate resulted in higher growth rate with BG-11 medium and higher EPS productivity with BG-11₀ medium (without NaNO₃). When the medium was supplemented with a mixture of glucose (4.0?g?L^?1) and acetate (2.0?g?L^?1), 1.79?g?L^?1 biomass with BG-11 medium and 879.6?mg?L^?1 of EPS production with BG-11₀ medium were achieved. Adopting this optimal ratio of glucose to acetate established in flask culture, the culture was also conducted in a 20-L photobioreactor with BG-11 medium for 7?days. A maximum biomass of 2.32?g?L^?1 was achieved, and the EPS production was 634.6?mg?L^?1.