Accumulation of an iodophilic polysaccharide during growth of Acetivibrio cellulolyticus on cellobiose

Maximum growth of Acetivibrio cellulolyticus in 1% cellobiose (w/v, added as filter sterilized solution) medium was observed after about 24h of incubation at 35°C. The metabolic end products of growth were H₂, CO₂, acetic acid, ethanol and glucose. Growth was adversely affected if cellobiose was autoclaved with the rest of the media ingredients. In the presence of an excess of cellobiose, the cells accumulated large quantities of an iodophilic polysaccharide (IPS). The maximum IPS accumulation (about 37% of the cell dry weight) was observed after about 12h growth under nitrogen-limiting conditions. Starvation of these cells anaerobically, in a pH 7.0 phosphate buffer for 10 h at 35°C, resulted in about 50% drop in the IPS. The results also indicated that A. cellulolyticus accumulated this iodophilic polysaccharide during growth on cellobiose but not during cultivation on cellulose.Abbreviation IPS iodophilic polysaccharide Issued as NRCC No. 19386     

Productivity and selective accumulation of carotenoids of the novel extremophile microalga <Emphasis Type="Italic">Chlamydomonas acidophila</Emphasis> grown with different carbon sources in batch systems

Cultivation of extremophile microorganisms has attracted interest due to their ability to accumulate high-value compounds. Chlamydomonas acidophila is an acidophile green microalga isolated by our group from Tinto River, an acidic river that flows down from the mining area in Huelva, Spain. This microalga accumulates high concentrations of lutein, a very well-known natural antioxidant. The aim of this study is to assess use of different carbon sources (CO₂, glucose, glycerol, starch, urea, and glycine) for efficient growth of and carotenoid production by C. acidophila. Our results reveal that growth of the microalga on different carbon sources resulted in different algal biomass productivities, urea being as efficient as CO₂ when used as sole carbon source (~20 g dry biomass m^–2 day^–1). Mixotrophic growth on glucose was also efficient in terms of biomass production (~14 g dry biomass m^–2 day^–1). In terms of carotenoid accumulation, mixotrophic growth on urea resulted in even higher productivity of carotenoids (mainly lutein, probably via α-carotene) than obtained with photoautotrophic cultures (70% versus 65% relative abundance of lutein, respectively). The accumulated lutein concentrations of C. acidophila reported in this work (about 10 g/kg dry weight, produced in batch systems) are among the highest reported for a microalga. Glycerol and glycine seem to enhance β-carotene biosynthesis, and when glycine is used as carbon source, zeaxanthin becomes the most accumulated carotenoid in the microalga. Strategies for production of lutein and zeaxanthin are suggested based on the obtained results.     

Heterotrophic production of lutein by selected Chlorella strains

Seven Chlorella strains representing three species obtained from culture collections and research laboratories were screened for their potential of heterotrophic production of lutein on two different media (Basal and Kuhl) containing glucose. While both media supported good growth and lutein formation of the seven strains in darkness, higher biomass concentrations and lutein content were achieved on Basal medium. Chlorella protothecoides CS-41 was chosen from the seven strains for further investigation due to its higher productivities of both biomass and lutein. The maximal biomass concentration and lutein content of C. protothecoides cultivated heterotrophically with 9 g L^-1 glucose in a 3.7-L fermentor were respectively 4.6 g dry cells L^-1 and 4.60 mg lutein g^-1 dry cells on Basal medium, and 4.0 g dry cells L^-1 and 4.36 mg lutein g^-1 dry cells on Kuhl medium. The heterotrophic cultivation process was scaled up successfully to 30 L using a fermentor, in which the Basal medium containing 36 g L^-1 glucose was used; the maximal biomass concentration of 16.4 g dry cells L^-1, specific growth rate of 0.92 d^-1,lutein content of 4.85 mg lutein g^-1 dry cells,growth yield of 0.47 g dry cells g^-1 glucose and lutein yield of 1.93 mg lutein g^-1 glucose were respectively achieved. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of nitrogen addition and drought on above-ground biomass of expanding tall grasses <Emphasis Type="Italic">Calamagrostis epigejos</Emphasis> and <Emphasis Type="Italic">Arrhenatherum elatius</Emphasis>

Tall expansive grasses act as serious weeds since they spread intensively and are a important threat to biodiversity of various plant communities. A field experiment was set up based on three sets of paired plots, where Calamagrostis epigejos and Arrhenatherum elatius dominated and a mixture of both these tall grasses occurred. Parallel plots were treated by additional amounts of nitrogen (50 kg N ha⁻¹) for six years (2002–2007). Above-ground biomass was harvested in both wet (2004) and dry (2007) years, separated in individual fractions, and weighed to determine the above-ground biomass. We wanted to know if a higher nitrogen availability in dry year can support above-ground growth of expansive tall grasses C. epigejos and A. elatius and what their competitive ability of these tall grasses in mixture is in dry conditions. Drought resulted in a decrease in above-ground biomass production of studied tall expansive grasses, and, in a relative increase in mortality of A. elatius shoots in comparison with C. epigejos. Drought can substantially reduce the effect of applied nitrogen on above-ground growth of expansive tall grasses. However, A. elatius appears to be producing more above-ground biomass after application of N even in relatively dry conditions.     

Dynamic change of metabolites and nutrients in suspension cells of <Emphasis Type="Italic">Panax Quinquefolium</Emphasis> L. in bioreactor

In order to understand how the nutrient elements were taken up during the cell growth as well as the production of metabolites, it was quite necessary to identify the dynamic change of metabolites and nutrients in suspension cells of Panax quinquefolium in bioreactor. In this study, dynamic accumulation of biomass and ginsenosides Re, Rb1 and polysaccharide as well as major nutrients consumption in cell suspension culture of P. quinquefolium in a 5-L stirred tank bioreactor were investigated. The dry cell weight and the contents of ginsenosides Re, Rb1 and polysaccharide reached the maximum peak simultaneously on about 21 days and the results showed that cell growth and metabolites synthesis related to nutrients consumption. For this reason, we supposed that the contents of metabolites can be increased through added nutrient at the right moment. These results provided theory reference for two-stage or continuous perfusion culture in suspension cells of P. quinquefolium in bioreactor.     

Influence of dilution rate on the morphology and technological properties ofLactobacillus delbrueckii subsp.bulgaricus

Lactobacillus delbrueckii subsp.bulgaricus ATCC 11842 was grown in a chemostat at 45°C and pH 5.5 using glucose as the carbon source, with the aim of optimizing biomass production. Cells were grown in a complex medium under nitrogen. At dilution rates lower than 0.18h^–1, it was difficult to keep steady-state conditions and pleomorphic forms were observed. The addition of 30mM Ca²⁺ and Mn²⁺ reverted the cells to normal shape: 30mM Mg²⁺ had no effect. Increasing the dilution rate resulted in normal morphology without the addition of any cations. Under these conditions, a maximum productivity of 1.24g dry biomass 1^–1 h^–1 was obtained. The maximum growth yield, corrected for maintenance, was 30g biomass mol^–1 glucose and the maintenance energy was 0.26g glucose g^–1 biomass h^–1. Lactate was the main fermentation product at all glucose concentrations used in the fed medium. Cells grown at high dilution rates had normal technological properties (acid production and proteolysis) when tested in milk.     

Control of starch and exocellular polysaccharides biosynthesis by gibberellic acid with cells of sweet potato cultured in vitro

The regulation of starch synthesis and exocellular polysaccharide synthesis by GA₃ was studied with cells of sweet potato grown as suspension in glycerol medium. In the presence of GA₃, and under normal cell growth, starch formation was inhibited. The incorporation activity (starch synthesis) from ADP-[¹⁴C] glucose or UDP-[¹⁴C] glucose with GA₃ treated cells was reduced. On the other hand, the synthesis of exocellular polysaccharides composed of glucose, galactose, mannose and arabinose etc., was stimulated and a clear increase of the Man/Ara ratio was observed in the presence of GA₃. These results may indicate that GA₃ affects the regulation of starch synthesis and exocellular polysaccharide synthesis.     

FLORIDOSIDE AS A CARBON PRECURSOR FOR THE SYNTHESIS OF CELL‐WALL POLYSACCHARIDE IN THE RED MICROALGA PORPHYRIDIUM SP. (RHODOPHYTA)1

Although red algae are known to be obligatory photoautotrophs, the red microalga Porphyridium sp. was shown to assimilate and metabolize floridoside. A pulse‐chase experiment with [¹⁴C]floridoside showed that at the end of a 240‐min pulse, 70% of total ¹⁴C‐uptake by the cells remained in the floridoside fraction. To evaluate the assimilation of floridoside by Porphyridium sp. cells, we exposed Porphyridium sp. not only to [¹⁴C]floridoside but also to its constituents, [¹⁴C]glycerol and [¹⁴C]galactose, as compared with [¹⁴C]bicarbonate. The extent of incorporation of [¹⁴C] galactose by the Porphyridium sp. cells was insignificant (50–80 dpm·mL^?1), whereas uptake of ¹⁴C from [¹⁴C]glycerol into the algal cells was evident (2.4 × 10³ dpm·mL^?1) after 60 min of the pulse. The pattern of ¹⁴C distribution among the major constituent sugars, xylose, glucose and galactose, of the labeled soluble polysaccharide was dependent on the ¹⁴C source. The relative content of [¹⁴C]galactose in the soluble polysaccharide was highest (28.8%) for [¹⁴C]floridoside‐labeled culture and lowest (19.8%) for the [¹⁴C]glycerol‐labeled culture. Upon incubation of [¹⁴C]floridoside with a crude extract of a cell‐free system prepared from nonlabeled cells of Porphyridium sp., the label was indeed found to be incorporated into the sulfated polysaccharide. Our results suggested that the carbon metabolic pathway in Porphyridium sp. passes through the low molecular weight photoassimilatory product—floridoside—toward sulfated cell‐wall polysaccharide production.     

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.     

Isolation of a mutant strain of Pseudomonas sp ATCC 31461 exhibiting elevated polysaccharide production

A mutant strain of the bacterium Pseudomonas sp. ATCC 31461 that exhibited elevated production of the polysaccharide gellan on glucose or corn syrup as a carbon source was isolated. Gellan production by the mutant strain was about twofold higher than its parent strain on glucose or corn syrup after 48 h of growth, and about 1.4-fold higher after 72 h. An increase in biomass production was not correlated with enhanced gellan synthesis by the mutant strain. The increased gellan production by the mutant strain on either carbon source resulted in an increase in its culture medium viscosity and the viscosity of the isolated polysaccharide produced by glucose-grown cells. No differences in the glucuronic acid content of the polysaccharides produced by the mutant and parent strains were observed. Journal of Industrial Microbiology & Biotechnology (2002) 29, 185–188 doi:10.1038/sj.jim.7000278 Received 13 February 2002/ Accepted in revised form 20 May 2002     

Effects of nitrogen on growth and carbohydrate formation in Porphyridium cruentum

The microalga Porphyridium cruentum (Rhodophyta) has several industrial and pharmaceutical uses, especially for its polysaccharide production. This study aimed to investigate the influence of nitrogen levels as reflected by altered N:P ratios on the production and content of biomass and carbohydrate. N:P molar ratios were altered in batch cultures to range from 1.6 to 50 using the Redfield ratio of 1:16 as reference. Algal growth (estimated as final cell number, biomass concentration and maximum specific growth rate) was negatively affected at low N:P ratios. The optimal N:P ratio for growth was identified at 35–50, with specific growth rates of 0.19 day^?1 and maximum cell concentrations of 59·10⁸ cells L^?1 and 1.2 g dry weight of biomass L^?1. In addition, variation in cell size was seen. Cells with larger diameters were at higher N:P ratios and smaller cells at lower ratios. The cellular carbohydrate content increased under reduced nitrogen availability. However, because accumulation was moderate at the lowest N:P ratio, 0.4 g per g dry weight biomass compared to 0.24 at the Redfield ratio of 16:1, conditions for increased total carbohydrate formation were identified at the N:P ratios optimal for growth. Additionally, carbohydrates were largely accumulated in late exponential to stationary phase.     

Formation of exopolysaccharides by Rhodococcus erythropolis and partial characterization of a heteropolysaccharide of high molecular weight

Summary Polysaccharide formation by Rhodococcus erythropolis was studied using lower mono-, di-and trihydric alcohols, sugars and n-alkanes as carbon sources. Cultural conditions of the organism were examined with regard to polysaccharide production. It was demonstrated that a glycerol substrate, an 30°C incubation temperature and a pH of 7.5 were optimal cultural conditions for polysaccharide formation. Addition of penicillin G in the decelerating growth phase increased the polysaccharide concentration in the culture filtrate to 3.1 g/l. One of the main extracellular heteropolysaccharides formed by Rhodococcus erythropolis consisted of glucose and mannose in the molar ratio 11, a small portion of protein and a trace of glucosamine. The molecular weight was to be 1·14×10⁶.     

Kinetic control of ethanol production by Zymomonas mobilis

Summary Zymomonas mobilis UQM 2716 was grown anaerobically in continuous culture (D = 0.1/h; 30° C) 3nder glucose or nitrogen limitation at pH 6.5 or 4.0. The rates of glucose consumption and ethanol production were lowest during glucose-limited growth at pH 6.5, but increased during growth at pH 4.0 or under nitrogen limitation, and were highest during nitrogen-limited growth at pH 4.0. The uncoupling agent CCCP substantially increased the rate of glucose consumption by glucose-limited cultures at pH 6.5, but had much less effect at pH 4.0. Washed cells also metabolised glucose rapidly, irrespective of the conditions under which the original cultures were grown, and the rates were variably increased by low pH and CCCP. Broken cells exhibited substantial ATPase activity, which was increased by growth at low pH. It was concluded that the fermentation rates of cultures growing under glucose or nitrogen limitation at pH 6.5, or under glucose limitation at pH 4.0, are determined by the rate at which energy is dissipated by various cellular activities (including growth, ATP-dependent proton extrusion for maintenance of the protonmotive force and the intracellular pH, and an essentially constitutive ATP-wasting reaction that only operates in the presence of excess glucose). During growth under nitrogen limitation at pH 4.0 the rate of energy dissipation is sufficiently high for the fermentation rate to be determined by the inherent catalytic activity of the catabolic pathway.Abbreviations CCCP carbonyl cyanide p-trifluoromethoxyphenylhydrazone - qG rate of glucose consumption (g glucose/g dry wt cells/h) - qE rate of ethanol production (g ethanol/g dry wt cells/h) - Y growth yield (g dry wt cells/g glucose) - D dilution rate Offprint requests to: C. W. Jones     

Physiological diversity within the <Emphasis Type="Italic">kluyveromyces marxianus</Emphasis> species

The Kluyveromyces marxianus strains CBS 6556, CBS 397 and CBS 712^T were cultivated on a defined medium with either glucose, lactose or sucrose as the sole carbon source, at 30 and 37°C. The aim of this work was to evaluate the diversity within this species, in terms of the macroscopic physiology. The main properties evaluated were: intensity of the Crabtree effect, specific growth rate, biomass yield on substrate, metabolite excretion and protein secretion capacity, inferred by measuring extracellular inulinase activity. The strain Kluyveromyces lactis CBS 2359 was evaluated in parallel, since it is the best described Kluyveromyces yeast and thus can be used as a control for the experimental setup. K. marxianus CBS 6556 presented the highest specific growth rate (0.70 h⁻¹) and the highest specific inulinase activity (1.65 U mg⁻¹ dry cell weight) among all strains investigated, when grown at 37°C with sucrose as the sole carbon source. The lowest metabolite formation and highest biomass yield on substrate (0.59 g dry cell weight g sucrose⁻¹) was achieved by K. marxianus CBS 712^T at 37°C. Taken together, the results show a systematic comparison of carbon and energy metabolism among three of the best known K. marxianus strains, in parallel to K. lactis CBS 2359.     

Production of a hypoglycemic, extracellular polysaccharide from the submerged culture of the mushroom, Phellinus linteus

Mycelial growth and extracellular polysaccharide production of Phellinus linteus were optimal at pH 5 and 25 °C. Maximum biomass production (14.2 g l^–1) was after 15 d of cultivation, whereas, extracellular polysaccharide was maximal (3.5 g l^–1) after 21 d. The hypoglycemic effect of the polysaccharide, investigated in streptozotocin-induced diabetic rats, decreased plasma glucose, total cholesterol and triacylglycerol concentrations by 49%, 32%, and 28%, respectively, and aspartate aminotransferase activity by 20%. The results indicate the potential of this polysaccharide to prevent hyperglycemia in diabetic patients.     

Bioreactor application on adventitious root culture of <Emphasis Type="Italic">Astragalus membranaceus</Emphasis>

Astragalus membranaceus is one of the most widely used traditional medicinal herbs in China, but the time required to generate a useful product in the field production is long. The growth of adventitious root cultures was compared between cultures grown in solid, liquid, or a 5-L balloon-type bubble bioreactor. The maximum growth ratio (final dry weight/initial dry weight) was determined for adventitious roots grown in the bioreactor. Studies carried out to optimize biomass production of adventitious roots compared adventitious root growth from various inoculum root lengths, inoculum densities, and aeration volume in the bioreactors. The maximum growth ratio occurred in treatments with a 1.5-cm inoculum root length, with 30 g (fresh weight) of inoculum per bioreactor or with an aeration volume of 0.1 vvm (air volume/culture medium volume per min). The polysaccharide, saponin, and flavonoid content of roots from bioreactor-grown cultures were compared to roots from field-grown plants grown for 1 and 3 yr. Total polysaccharide content of adventitious roots in the bioreactor (30.0 mg g⁻¹ dry weight (DW)) was higher than the roots of 1-yr-old (13.8 mg g⁻¹ DW) and 3-yr-old (21.1 mg g⁻¹ DW) plants in the field. Total saponin (3.4 mg g⁻¹ DW) and flavonoid (6.4 mg g⁻¹ DW) contents were nearly identical to 3-yr-old roots and higher than that of 1-yr-old roots under field cultivation.     

Regulatory flexibility of methylotrophic yeasts in chemostat cultures: Simultaneous assimilation of glucose and methanol at a fixed dilution rate

The influence of the composition of methanol/glucose-mixtures as only sources of carbon and energy on growth and regulation of the synthesis of enzymes involved in methanol-dissimilation was studied under chemostat conditions at a fixed dilution rate with the methylotrophic yeasts Hansenula polymorpha and Kloeckera sp. 2201. Both carbon sources were found to be utilized completely independently of the composition of the C₁/C₆ mixture. Using mixtures of ¹⁴C-labelled methanol and glucose the growth yield for glucose was found to be constant for all C₁/C₆-mixtures tested and both yeasts. The growth yield for methanol, however, was reduced by up to 25% when the proportion of methanol in the inflowing medium was lower than 20% (w/w with respect to glucose) for H. polymorpha and 50% (w/w with respect to glucose) for Kloeckera sp. 2201 respectively. During growth with C₁/C₆-mixtures containing higher C₁-proportions of methanol regular growth yields for methanol were recorded which corresponded to the growth yields found with methanol as the only carbon source.The regulation of the synthesis of the enzymes of the dissimilatory pathway for methanol was found to be under multiple control. Although glucose was present in the medium methanol had a positive effect on the synthesis of these enzymes. Thus, in addition to derepression induction by methanol was also observed. This inductive effect was found to increase with increasing proportions of methanol in the mixture. Depending on the enzyme, 10–40% methanol in the mixture resulted in a maximal induction with enzyme specific activities equal to those found in cells grown with methanol as the only carbon source. No further enhancements in enzyme specific activities were observed during growth on mixtures containing more than 40% methanol.Abbreviations and terms C₁ Methanol - C₆ glucose - C₁/C₆ mixture compositions are given in % (w/w) - C₀ concentration of ¹⁴C in the inflowing medium (DPM ml^-1) - C(t) concentration of ¹⁴C incorporated in cells as a function of time t (DPM ml^-1) - d dilution rate (h^-1) - DPM disintegrations per minute - q _s q _C1 and q _C6 are specific rates of consumption of substrate, methanol and glucose respectively [g (g cell dry weight)^-1 h^-1] - q _O2 and q _CO2 are the specific rates of oxygen consumption and carbon dioxide release [mmol (g cell dry weight)^-1 h^-1] - RQ respiration quotient (q _CO2 q _O2 ^-1) - s _C1 and s _C6 are the residual concentrations of methanol and glucose in the culture liquid (g l^-1) - s _O/C1 and s _O/C6 are the concentrations of methanol and glucose in the inflowing medium (g l^-1) - Sp.A. enzyme specific activity - x cell dry weight concentration (g l^-1) - Y _X/C1 and Y _X/C6 are growth yields on methanol and glucose respectively (g cell dry weight (g substrate)^-1 - Y _C/C1 growth yield with methanol with respect to carbon (g carbon assimilated (g carbon supplied)^-1 - _m maximum specific growth rate (h^-1)     

H2 production from chemostat fermentation of glucose byClostridium butyricum andClostridium pasteurianum in ammonium- and phosphate limitation

Summary In ammonium-limitation (4.55 mM NH₄ ⁺) at a dilution rate (D)=0.081 h^–1,Clostridium butyricum produced 2 mol H₂ per mol glucose consumed at pH 5.0, but at a low fermentation rate. At higher pH, important amounts of extracellular protein were produced. Phosphatelimitation (0.5 mM PO₄ ^–3) at D=0.061 h^–1 and pH 7.0 were the best conditions tested for hydrogen gas production (2.22 mol H₂ per mol glucose consumed) at a high fermentation rate. Steady-state growth at lower pH and with 0.1 mM PO₄ ^–3 resulted in proportional higher glucose incorporation into biomass and lower H₂ production. C. pasteurianum in NH₄ ⁺ limitation showed higher fermentation rates thanC. butyricum and a stabilized H₂ production around 2.08 (±0.06) mol per mol glucose consumed at various defined pH conditions, although the acetate/butyrate ratio increased to 1 at pH 7.0. The latter was also observed in phosphate-limitation, but here H₂ production was maximal (1.90 mol. per mol glucose consumed) at the lowest pH (5.5) tested.     

Cadmium biosorption by <Emphasis Type="Italic">Bacillus</Emphasis><Emphasis Type="Italic"> circulans</Emphasis> strain EB1

Summary A heavy metal resistant bacterium, Bacillus circulans strain EB1 showed a high cadmium biosorption capacity coupled with a high tolerance to this metal when grown in its presence. Bacillus circulans EB1 cells grown in the presence of 28.1 mg cadmium/l were capable of removing cadmium with a specific biosorption capacity of 5.8 mg Cd/g dry wt biomass in the first 8 h. When the cells were pre-conditioned with low concentrations of cadmium in pre-grown medium, the uptake was increased to 6.7 mg Cd/g dry wt biomass. The maximum uptake of␣cadmium was during mid-logarithmic phase of growth. The resting cells (both wet and dry) of EB1 were also able to biosorb cadmium. Specific biosorption capacities of wet and dry biomass were 9.8 and 26.5 mg Cd/g dry wt biomass, respectively. Maximum cadmium removals by both wet and dry cells were at pH 7.0. The results showed that the cadmium removal capacity of resting cells was markedly higher than that of growing cells. Since both growing and resting cells had a high biosorption capacity for cadmium, EB1 cells could serve as an excellent biosorbent for removal of cadmium from natural environments.     

Polysaccharide Elicitor from the Endophyte <i>Bionectria</i> sp. Fat6 Improves Growth of Tartary Buckwheat under Drought Stress

Drought can limit the growth and reduce the yield of crops, but the safe and effective bio-approach to improve the drought resistance of crops is very little. We conducted an experiment in which we monitored the effects of polysaccharide from the endophyte Bionectria sp. Fat6 on the growth of Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn) seedlings under control and drought-stressed conditions by determining gas exchange, photosynthesis parameters, photosynthetic pigment contents, and metabolite accumulation. Results indicated that the polysaccharide from endophyte stimulated plant growth and increased the aboveground biomass, root mass, and root/shoot ratio of Tartary buckwheat. Application of the polysaccharide to drought-stressed plants resulted in a significant increase in the net photosynthetic rate, stomatal conductance, and transpiration rate of Tartary buckwheat and decreased the intercellular CO₂ concentration. The contents of chlorophyll a, chlorophyll b, chlorophyll a + b, and carotenoids in leaves were higher in polysaccharide-treated seedlings than that in control. Polysaccharide notably increased the soluble protein and proline content and decreased the malondialdehyde content in Tartary buckwheat leaves. The endophytic polysaccharide may protect Tartary buckwheat against drought by improving leaf gas exchange and photosynthetic capacity, and altering concentrations of protective metabolites. Together, these changes may compensate for the negative impacts of drought stress on the growth of Tartary buckwheat. Thus, the polysaccharide from the endophyte Bionectria sp. Fat6 may be an effective biotic elicitor and a promising bio-approach to improve Tartary buckwheat production worldwide.