Production of recombinant beta-amylase of Bacillus aryabhattai

In this study, the effects of carbon source, nitrogen source, and metal ions on cell growth and Bacillus aryabhattai β-amylase production in recombinant Brevibacillus choshinensis were investigated. The optimal medium for β-amylase production, containing glucose (7.5?g·L^?1), pig bone peptone (40.0?g·L^?1), Mg²⁺ (0.05?mol·L^?1), and trace metal elements, was determined through single-factor experiments in shake flasks. When cultured in the optimized medium, the β-amylase yield reached 925.4?U mL^?1, which was 7.2-fold higher than that obtained in the initial medium. Besides, a modified feeding strategy was proposed and applied in a 3-L fermentor fed with glucose, which achieved a dry cell weight of 15.4?g L^?1. Through this cultivation approached 30?°C with 0?g·L^?1 initial glucose concentration, the maximum β-amylase activity reached 5371.8?U mL^?1, which was 41.7-fold higher than that obtained with the initial medium in shake flask.     

Highly thermo–halo–alkali-stable β-1,4-endoxylanase from a novel polyextremophilic strain of Bacillus halodurans

A novel bacterial isolate, capable of producing extracellular highly thermostable, halo-alkali-stable and cellulase-free xylanase, was isolated from soil and identified as Bacillus halodurans TSPV1 by polyphasic approach. The Plackett–Burman design identified wheat bran, lactose, tryptone and NaCl as the factors that significantly affect xylanase production, and thus, these were optimized by response surface methodology. The data analysis suggested that optimum levels of wheat bran (15–20 g L^?1), lactose (1.0–1.5 g L^?1), tryptone (2–2.5 g L^?1) and NaCl (7.0–8.0 g L^?1) support 6.75-fold higher xylanase production than that in the un-optimized medium. The xylanase is optimally active at 90 °C and pH 10, and stable for 4 h at 90 °C (T _1/2 60 h) over a broad range of NaCl concentrations (0–29 %). This is the first report on the isolation of polyextremophilic B. halodurans strain that produces thermo-halo-alkali-stable xylanase in submerged fermentation. This enzyme efficiently saccharifies agro residues like wheat bran and corncobs. Fifty-six percent of hemicellulose of wheat bran could be hydrolyzed by xylanase (100 U g^?1 substrate) along with cellulase (22 U FPase and 50 U CMCase g^?1). The xylanase, being thermo-alkali stable and cellulase free, can find applications in pre-bleaching of paper pulps and hydrolysis of xylan in agricultural residues.     

Optimal C:N ratio for the production of red pigments by Monascus ruber

The carbon-to-nitrogen (C:N) ratio in the biomass of microfungi tends to be quite different (e.g. 10–15) compared with the C:N ratio in the red pigments (e.g. >20) of the fungus Monascus ruber. Therefore, determining an optimal C:N ratio in the culture medium for maximizing the production of the pigments is important. A culture medium composition is established for maximizing the production of the red pigment by the fungus M. ruber ICMP 15220 in submerged culture. The highest volumetric productivity of the red pigment was 0.023 AU L^?1 h^?1 in a batch culture (30 °C, initial pH of 6.5) with a defined medium of the following composition (g L^?1): glucose (10), monosodium glutamate (MSG) (10), MgSO₄·7H₂O (0.5), KH₂PO₄ (5), K₂HPO₄ (5), ZnSO₄·7H₂O (0.01), FeSO₄·7H₂O (0.01), CaCl₂ (0.1), MnSO₄·H₂O (0.03). This medium formulation had a C:N mole ratio of 9:1. Under these conditions, the specific growth rate of the fungus was 0.043 h^?1 and the peak biomass concentration was 6.7 g L^?1 in a 7-day culture. The biomass specific productivity of the red pigment was 1.06 AU g^?1 h^?1. The best nitrogen source proved to be MSG although four other inorganic nitrogen sources were evaluated.     

Biomass and Lipid Production of Dinoflagellates and Raphidophytes in Indoor and Outdoor Photobioreactors

The principal fatty acids from the lipid profiles of two autochthonous dinoflagellates (Alexandrium minutum and Karlodinium veneficum) and one raphidophyte (Heterosigma akashiwo) maintained in bubble column photobioreactors under outdoor culture conditions are described for the first time. The biomass production, lipid content and lipid productivity of these three species were determined and the results compared to those obtained when the strains were cultured indoors. Under the latter condition, the biotic values did not significantly differ among species, whereas under outdoor conditions, differences in both duplication time and fatty acids content were observed. Specifically, A. minutum had higher biomass productivity (0.35 g·L^?1 day^?1), lipid productivity (80.7 mg lipid·L^?1 day^?1) and lipid concentration (252 mg lipid·L^?1) at harvest time (stationary phase) in outdoor conditions. In all three strains, the growth rate and physiological response to the light and temperature fluctuations of outdoor conditions greatly impacted the production parameters. Nonetheless, the species could be successfully grown in an outdoor photobioreactor and were of sufficient robustness to enable the establishment of long-term cultures yielding consistent biomass and lipid production.     

Enhanced citric acid production by a yeast <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> over-expressing a pyruvate carboxylase gene

In this study, after the expression of a pyruvate carboxylase gene (PYC) cloned from Meyerozyma guilliermondii in a marine-derived yeast Yarrowia lipolytica SWJ-1b, a transformant PG86 obtained had much higher PYC activity than Y. lipolytica SWJ-1b. At the same time, the PYC gene expression and citric acid (CA) production by the transformant PG86 were also greatly enhanced. When glucose concentration in the medium was 60.0 g L^?1, CA concentration formed by the transformant PG86 was 34.02 g L^?1, leading to a CA yield of 0.57 g g^?1 of glucose. During a 10-L fed-batch fermentation, the final concentration of CA was 101.0 ± 1.3 g L^?1, the yield was 0.89 g g^?1 of glucose, the productivity was 0.42 g L^?1 h^?1 and only 5.93 g L^?1 reducing sugar was left in the fermented medium within 240 h of the fed-batch fermentation. HPLC analysis showed that most of the fermentation products were CA.     

Elicitor mediated enhancement of wedelolactone in cell suspension culture of <Emphasis Type="Italic">Eclipta alba</Emphasis> (L.) Hassk

The present research focused on enhancing the production of wedelolactone through cell suspension culture (CSC) in Eclipta alba (L.) Hassk. With an aim of attaining a sustainable CSC, various plant growth regulators, elicitors and agitation speed were examined. Nodal segments of in vitro propagated plantlets induced the maximum percentage (93.47?±?0.61%) of callus inoculated on Murashige and Skoog (MS) medium fortified with picloram (2 mg L^?1). The growth kinetics of CSC exhibited a sigmoid pattern with a lag phase (0–6 days), a log phase (6–18 days), a stationary phase (18–24 days) and then death phase thereafter. The highest biomass accumulation in CSC with 7.09?±?0.06 g 50 mL^?1 fresh weight, 1.52?±?0.02 g 50 mL^?1 dry cell weight, 1.34?±?0.01?×?10⁶ cell mL^?1 total cell count and 57.00?±?0.58% packed cell volume was obtained in the liquid MS medium supplemented with 1.5 mg L^?1 picloram plus 0.5 mg L^?1 kinetin at 120 rpm. High performance thin layer chromatography confirmed that yeast extract (biotic elicitor) at 150 mg L^?1 accumulated more CSC biomass with 1.22-fold increase in wedelolactone (288.97?±?1.94 µg g^?1 dry weight) content in comparison to the non-elicited CSC (237.78?±?0.04 µg g^?1 dry weight) after 120 h of incubation. Contrastingly, methyl jasmonate (abiotic elicitor) did not alter the biomass but increased the wedelolactone content (259.32?±?1.06 µg g^?1 dry weight) to an extent of 1.09-fold at 100 µM. Complete plantlet regeneration from CSC was possible on MS medium containing N⁶-benzyladenine (0.75 mg L^?1) and abscisic acid (0.5 mg L^?1). Thus, the establishment of protocol for CSC constitutes the bases for future biotechnological improvement studies in this crop.     

Effect of different media on exopolysaccharide and biomass production by the green microalga Botryococcus braunii

Botryococcus braunii is a colonial green microalga with recognized potential to synthesize lipids and hydrocarbons for biofuel production. Besides this ability, this microalga also produces exopolysaccharides (EPS). Nevertheless, there are few reports about their biotechnological aspects and industrial applications. In this study, the effect of the nutritional conditions was examined by using two different culture media (BG11 and D medium). To our knowledge, the latter has not been reported before for culturing B. braunii. After 49 days of incubation, the final production of EPS was found to be statistically higher (P < 0.05) in the D medium (0.549?±?0.044 g L^?1) than in BG11 (0.336?±?0.009 g L^?1). On the contrary, the biomass production was found to be higher in BG11 (1.019?±?0.051 g L^?1) than in the D medium (0.953?±?0.056 g L^?1). However, this difference was not statistically significant. The difference in salinity and nitrogen concentration between both media is suggested as the main factor involved in the EPS and biomass results. FTIR spectra of B. braunii EPS from both media revealed presence of uronic acids and absence of amino and sulfate groups. Despite the similarity between both spectra, there were some different signals (at 1,921.52 and 720.60 cm^?1) which may mean a difference in glycosyl composition.     

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.     

Enhancing ethanol production from cellulosic sugars using <Emphasis Type="Italic">Scheffersomyces (Pichia) stipitis</Emphasis>

Studies were performed on the effect of CaCO₃ and CaCl₂ supplementation to fermentation medium for ethanol production from xylose, glucose, or their mixtures using Scheffersomyces (Pichia) stipitis. Both of these chemicals were found to improve maximum ethanol concentration and ethanol productivity. Use of xylose alone resulted in the production of 20.68 ± 0.44 g L^?1 ethanol with a productivity of 0.17 ± 0.00 g L^?1 h^?1, while xylose plus 3 g L^?1 CaCO₃ resulted in the production of 24.68 ± 0.75 g L^?1 ethanol with a productivity of 0.21 ± 0.01 g L^?1 h^?1. Use of xylose plus glucose in combination with 3 g L^?1 CaCO₃ resulted in the production of 47.37 ± 0.55 g L^?1 ethanol (aerobic culture), thus resulting in an ethanol productivity of 0.39 ± 0.00 g L^?1 h^?1. These values are 229 % of that achieved in xylose medium. Supplementation of xylose and glucose medium with 0.40 g L^?1 CaCl₂ resulted in the production of 44.84 ± 0.28 g L^?1 ethanol with a productivity of 0.37 ± 0.02 g L^?1 h^?1. Use of glucose plus 3 g L^?1 CaCO₃ resulted in the production of 57.39 ± 1.41 g L^?1 ethanol under micro-aerophilic conditions. These results indicate that supplementation of cellulosic sugars in the fermentation medium with CaCO₃ and CaCl₂ would improve economics of ethanol production from agricultural residues.     

CITRIC ACID PRODUCTION BY Candida SPECIES GROWN ON A SOY-BASED CRUDE GLYCEROL

Citric acid was produced by five species of the yeast Candida after growth on a medium containing soy biodiesel-based crude glycerol. After growth on a medium containing 10 g L^?1 or 60 g L^?1 crude glycerol for 168 hr at 30°C, Candida parapsilosis ATCC 7330 and C. guilliermondii ATCC 9058 produced the highest citric acid levels. On 10 g L^?1 or 60 g L^?1 crude glycerol for 168 hr at 30°C, the citric acid level produced by C. parapsilosis ATCC 7330 was 1.8 g L^?1 or 11.3 g L^?1, respectively, while C. guilliermondii ATCC 9058 produced citric acid concentrations of 3.0 g L^?1 or 10.4 g L^?1, respectively. Biomass production by C. guilliermondii ATCC 9058 on 10 g L^?1 or 60 g L^?1 crude glycerol for 168 hr at 30°C was highest at 1.2 g L^?1 or 6.9 g L^?1, respectively. The citric acid yields observed for C. guilliermondii ATCC 9058 after growth on 10 g L^?1 or 60 g L^?1 crude glycerol (0.35 g g^?1 or 0.21 g g^?1, respectively) were generally higher than for the other Candida species tested. When similar crude glycerol concentrations were present in the culture medium, citric acid yields observed for some of the Candida species utilized in this study were about the same or higher compared to citric acid yields by Yarrowia lipolytica strains. Based on the findings, it appeared that C. guilliermondii ATCC 9058 was the most effective species utilized, with its citric acid production being similar to what has been observed when citric acid-producing strains of Y. lipolytica were grown on crude glycerol under batch conditions that could be of significance to biobased citric acid production.     

Selective fengycin production in a modified rotating discs bioreactor

Production of lipopeptides fengycin and surfactin in rotating discs bioreactor was studied. The effects of rotation velocity and the addition of agitators between the discs on volumetric oxygen transfer coefficient k _L a were firstly studied in model media. Then the production of lipopeptides was also studied at different agitation conditions in the modified bioreactor (with agitators). The effect of agitation on dissolved oxygen, on submerged and immobilized biomass, on lipopeptide concentrations and yields and on the selectivity of the bioreaction was elucidated and discussed. The proposed modified rotating discs bioreactor allowed to obtain high fengycin concentrations (up to 787 mg L^?1), but also better selectivity of the bioreaction towards fengycin (up to 88 %) and better yields of fengycin per glucose (up to 62.9 mg g^?1), lipopeptides per glucose (up to 71.5 mg g^?1), fengycin per biomass (up to 309 mg g^?1) and lipopeptides per biomass (up to 396 mg g^?1) than those reported in the literature. Highest fengycin production and selectivity were obtained at agitation velocity of 30 min^?1. The proposed non-foaming fermentation process could contribute to the scale-up of lipopeptide fermentors and promote the industrial production of fengycin. The proposed bioreactor and bioprocess could be very useful also for the production of other molecules using bioprocesses requiring bubbleless oxygen supply.     

Simplified feeding strategies for the fed-batch cultivation of Kluyveromyces lactis GG799 for enhanced recombinant xylanase production

A xylanase gene (xyn2) from Trichoderma reesei ATCC 58350 was previously cloned and expressed in Kluyveromyces lactis GG799. The production of the recombinant xylanase was conducted in a developed medium with an optimised batch and with fed-batches that were processed with glucose. The glucose served as a carbon source for cell growth and as an inducer for xylanase production. In a 1-L batch system, a glucose concentration of 20 g L^?1 and 80 % dissolved oxygen were found to provide the best conditions for the tested ranges. A xylanase activity of 75.53 U mL^?1 was obtained. However, in the batch mode, glucose depletions reduced the synthesis of recombinant xylanase by K. lactis GG799. To maximise the production of xylanase, further optimisation was performed using exponential feeding. We investigated the effects of various nitrogen sources combined with the carbon to nitrogen (C/N) molar ratio on the production of xylanase. Of the various nitrogen sources, yeast extract was found to be the most useful for recombinant xylanase production. The highest xylanase production (110.13 U mL^?1) was measured at a C/N ratio of 50.08. These conditions led to a 45.8 % increase in xylanase activity compared with the batch cultures. Interestingly, the further addition of 500 g L^?1 glucose led to a 6.2-fold increase (465.07 U mL^?1) in recombinant xylanase activity. These findings, together with those of the exponential feeding strategy, indicate that the composition of the C/N molar ratio has a substantial impact on recombinant protein production in K. lactis.     

Simultaneous production of propionic acid and vitamin B12 from corn stalk hydrolysates by Propionibacterium freudenreichii in an expanded bed adsorption bioreactor

Abstract

Vitamin B12 and propionic acid that were simultaneous produced by Propionibacterium freudenreichii are both favorable chemicals widely used in food preservatives, medicine, and nutrition. While the carbon source and propionic acid accumulation reflected fermentation efficiency. In this study, using corn stalk as a carbon source and fed-batch fermentation process in an expanded bed adsorption bioreactor was studied for efficient and economic biosynthesis of acid vitamin B12 and propionic. With liquid hot water pretreated corn stalk hydrolysates as carbon source, 28.65?mg L^?1 of vitamin B12 and 17.05?g L^?1 of propionic acid were attained at 168?h in batch fermentation. In order to optimize the fermentation outcomes, fed-batch fermentation was performed with hydrolyzed corn stalk in expanded bed adsorption bioreactor (EBAB), giving 47.6?mg L^?1 vitamin B12 and 91.4?g L^?1 of propionic acid at 258?h, which correspond to product yields of 0.37?mg g^?1 and 0.75?g g^?1, respectively. The present study provided a promising strategy for economically sustainable production of vitamin B12 and propionic acid by P. freudenreichii fermentation using biomass cornstalk as carbon source and expanded bed adsorption bioreactor.     

Influence of the concentrations of d-xylose and yeast extract on ethanol production by Pachysolen tannophilus

To determine the most favorable conditions for the production of ethanol by Pachysolen tannophilus, this yeast was grown in batch cultures with various initial concentrations of two of the constituents of the culture medium: d-xylose (s_o), ranging from 1 g·l⁻¹ to 200 g·l⁻¹, and yeast extract (l_o), ranging from 0 g·l⁻¹ to 8 g·l⁻¹. The most favorable conditions proved to be initial concentrations of S_o=25 g·l⁻¹ and l_o=4 g·l⁻¹, which gave a maximum specific growth rate of 0.26 h⁻¹, biomass productivity of 0.023 g·l⁻¹·h⁻¹, overall biomass yield of 0.094 g·g⁻¹, specific xylose-uptake rate (q_s) of 0.3 g·g⁻¹·h⁻¹ (for t=50 h), specific ethanol-production rate (q_E) of 0.065 g·g⁻¹·h⁻¹ and overall ethanol yield of 0.34 g·g⁻¹; q_s values decreased after the exponential growth phase while q_E remained practically constant.     

Succinic acid-producing biofilms of Actinobacillus succinogenes: reproducibility,stability and productivity

Continuous anaerobic fermentations were performed in a biofilm reactor packed with Poraver® beads. Dilution rates (D) varied between 0.054 and 0.72 h^?1, and d-glucose and CO₂ gas were used as carbon substrates. Steady-state conditions were shown to be repeatable and independent of the operational history. Production stability was achieved over periods exceeding 80 h at values of D below 0.32 h^?1. In these situations, steady-state variation (expressed as fluctuations in NaOH neutralisation flow rates) exhibited a standard deviation of less than 5 % while no indication of biofilm deactivation was detected. The total biomass amount was found to be independent of the dilution rate with an average dry concentration of 23.8?±?2.9 g L^?1 obtained for all runs. This suggests that the attachment area controls the extent of biofilm accumulation. Specific succinic acid (SA) productivities, based on the total biomass amount, exhibited a substantial decrease with decreasing D. An SA volumetric productivity of 10.8 g L^?1 h^?1 was obtained at D?=?0.7 h^?1—the highest value reported to date in Actinobacillus succinogenes fermentations. SA yields on glucose increased with decreasing D, with a yield of 0.90?±?0.01 g g^?1 obtained at a D of 0.054 h^?1. Production of formic acid approached zero with decreasing D, while the succinic to acetic acid ratio increased with decreasing D, resulting in an increasing SA yield on glucose.     

Culture Media Statistical Optimization for Biomass Production of a Ligninolytic Fungus for Future Rice Straw Degradation

The main objective of this study was to optimize a culture media for low scale biomass production of Pleurotus spp. Future applications of this optimization will be implemented for “in situ” rice straw degradation, increase soil nutrients availability, and lower residue and rice culture management costs. Soil samples were taken from different points in six important rice production cities in Colombia. For carbon and nitrogen source selection a factorial 4² design was carried out. The Plackett-Burman design permitted to detect carbon, nitrogen and inducer effects on fungus growth (response variable for all designs). This optimization was carried out by a Box-Behnken design. Finally a re-optimization assay for glucose concentration was performed by means of a One Factor design. Only 4/33 (12 %) isolates showed and important laccase or manganese peroxidase activity compared to Pleurotus ostreatus (HPB/P3). We obtained an increased biomass production in Pleurotus spp. (T1.1.) with glucose, followed by rice husk. Rice straw was considered an inducing agent for lignin degradation. Glucose was a significant component with positive effects, whereas Tween 80 and pH had negative effects. On the contrary, rice husk, yeast extract and CaCl₂ were not significant components for increase the biomass production. Final media composition consisted of glucose 25 g L^?1, yeast extract 5 g L^?1, Tween 80 0.38 % (v/v), Rice husk 10 g L^?1, CaCl₂ 1 g L^?1, and pH 4.88 ± 0.2. The Box-Behnken polynomial prediction resulted to be lower than the experimental validation of the model (6.59 vs. 6.91 Log₁₀ CFU ml^?1 respectively).     

Continuous succinic acid production from xylose by <Emphasis Type="Italic">Actinobacillus succinogenes</Emphasis>

Continuous, anaerobic fermentations of D-xylose were performed by Actinobacillus succinogenes 130Z in a custom, biofilm reactor at dilution rates of 0.05, 0.10 and 0.30 h^?1. Succinic acid yields on xylose (0.55–0.68 g g^?1), titres (10.9–29.4 g L^?1) and productivities (1.5–3.4 g L^?1 h^?1) were lower than those of a previous study on glucose, but product ratios (succinic acid/acetic acid = 3.0–5.0 g g^?1) and carbohydrate consumption rates were similar. Also, mass balance closures on xylose were up to 18.2 % lower than those on glucose. A modified HPLC method revealed pyruvic acid excretion at appreciable concentrations (1.2–1.9 g L^?1) which improved the mass balance closure by up to 16.8 %. Furthermore, redox balances based on the accounted xylose consumed and the excreted metabolites, indicated an overproduction of reducing power. The oxidative pentose phosphate pathway was shown to be a plausible source of the additional reducing power.     

The citric acid production from raw glycerol by Yarrowia lipolytica yeast and its regulation

The optimal cultivation conditions ensuring the maximal rate of citric acid (CA) biosynthesis by glycerol-grown mutant Yarrowia lipolytica NG40/UV7 were found to be as follows: growth limitation by inorganic nutrients (nitrogen, phosphorus, or sulfur), 28 °C, pH 5.0, dissolved oxygen concentration (pO₂) of 50 % (of air saturation), and pulsed addition of glycerol from 20 to 80 g L^?1 depending on the rate of medium titration. Under optimal conditions of fed-batch cultivation, in the medium with pure glycerol, strain Y. lipolytica NG40/UV7 produced 115 g L^?1 of CA with the mass yield coefficient of 0.64 g g^?1 and isocitric acid (ICA) amounted to 4.6 g L^?1; in the medium with raw glycerol, CA production was 112 g L^?1 with the mass yield coefficient of 0.90 g g^?1 and ICA amounted to 5.3 g L^?1. Based on the activities of enzymes involved in the initial stages of raw glycerol assimilation, the tricarboxylic acid cycle and the glyoxylate cycle, the mechanism of increased CA yield from glycerol-containing substrates in Y. lipolytica yeast was explained.     

A Review of: “North-Holland Publishing Company,Amsterdam, New York,Oxford, 1976; Softbound, 290 pages, $ 19.25.”

Several factors affecting erythritol production from glycerol by Yarrowia lipolytica Wratislavia K1 strain were examined in batch fermentations. Ammonium sulfate, monopotassium phosphate, and sodium chloride were identified as critical medium components that determine the ratio of polyols produced. The central composite rotatable experimental design was used to optimize medium composition for erythritol production. The concentrations of ammonium sulfate, monopotassium phosphate, and sodium chloride in the optimized medium were 2.25, 0.22, and 26.4 g L^?1, respectively. The C:N ratio was found as 81:1. In the optimized medium with 100 g L^?1 of glycerol the Wratislavia K1 strain produced 46.9 g L^?1 of erythritol, which corresponded to a 0.47 g g^?1 yield and a productivity of 0.85 g L^?1 hr^?1. In the fed-batch mode and medium with the total concentration of glycerol at 300 g L^?1 and C:N ratio at 81:1, 132 g L^?1 of erythritol was produced with 0.44 g g^?1 yield and a productivity of 1.01 g L^?1 hr^?1.     

Different fermentation strategies by Schizochytrium mangrovei strain pq6 to produce feedstock for exploitation of squalene and omega‐3 fatty acids

Schizochytrium mangrovei strain PQ 6 was investigated for coproduction of docosahexaenoic acid (C22: 6ω‐3, DHA ) and squalene using a 30‐L bioreactor with a working volume of 15 L under various batch and fed‐batch fermentation process regimes. The fed‐batch process was a more efficient cultivation strategy for achieving higher biomass production rich in DHA and squalene. The final biomass, total lipid, unsaponifiable lipid content, and DHA productivity were 105.25 g · L^?1, 43.40% of dry cell weight, 8.58% total lipid, and 61.66 mg · g^?1 · L^?1, respectively, after a 96 h fed‐batch fermentation. The squalene content was highest at 48 h after feeding glucose (98.07 mg · g^?1 of lipid). Differences in lipid accumulation during fermentation were correlated with changes in ultrastructure using transmission electron microscopy and Nile Red staining of cells. The results may be of relevance to industrial‐scale coproduction of DHA and squalene in heterotrophic marine microalgae such as Schizochytrium .