Enhancement of polysaccharide production in suspension cultures of protocorm-like bodies from Dendrobium huoshanense by optimization of medium compositions and feeding of sucrose

A strategy that optimization of medium compositions for maximum biomass followed by feeding of sucrose for maximum polysaccharide synthesis was developed for enhancing polysaccharide production in suspension culture of protocorm-like bodies (PLBs) of Dendrobium huoshanense C.Z. Tang et S.J. Cheng. In growth stage, the original half-strength MS medium was optimized with carbon sources, nitrogen sources and metal ion combinations. The effects of different carbon sources on PLBs growth were remarkable and sucrose at 35 g l⁻¹ was the most suitable. Sole nitrate nitrogen of 30 mmol l⁻¹ was the best for PLBs growth. Metal ions (Ca²⁺, Fe²⁺, Mn²⁺ and Zn²⁺) showed different influences on PLBs growth. The optimal concentration of Ca²⁺, Fe²⁺, Mn²⁺ and Zn²⁺ was 4.5 mmol l⁻¹, 0.1 mmol l⁻¹, 0.5 mmol l⁻¹ and 0.06 mmol l⁻¹, respectively. In the optimized medium (sucrose, nitrate, Ca²⁺, Fe²⁺, Mn²⁺ and Zn²⁺ concentration as described above, the other component concentration seen in half-strength MS), 33.9 g DW l⁻¹ PLBs were harvested after 30 days of culture and biomass increase was improved 245% as compared with that in the original medium. In production stage, polysaccharide synthesis was significantly improved by the feeding sucrose. The maximum polysaccharide production (22 g l⁻¹) was obtained in the case of 50 g l⁻¹ sucrose feeding at day 30 of culture, which was about 109-fold higher than that in the original medium without feeding of sucrose.     

A stable immobilized d-psicose 3-epimerase for the production of d-psicose in the presence of borate

Maximal activity of the immobilized d-psicose 3-epimerase from Agrobacterium tumefaciens on Duolite A568 beads was achieved at pH 9.0 and 55 °C with borate, and at pH 8.5 and 50 °C without borate. The half-lives of the immobilized enzyme at 50 °C with and without borate were increased 4.2- and 128-fold compared to that of the free enzyme without borate, respectively. The immobilized enzyme with borate produced 441 g l^?1 psicose from 700 g l^?1 fructose at pH 9.0 and 55 °C, whereas 193 g l^?1 psicose was produced without borate at pH 8.5 and 50 °C after 120 min in a batch reaction. The immobilized enzyme in a packed-bed bioreactor without borate was produced continuously 325 g l^?1 psicose from 500 g l^?1 fructose at a dilution rate of 1.62 h^?1 over a 236 h period with productivity of 527 g l^?1 h^?1 while that without borate produced 146 g l^?1 psicose at 4.15 h^?1 over a 384-h period with productivity of 606 g l^?1 h^?1. The operational half-lives of the enzyme with and without borate in the bioreactor were 601 and 645 h, respectively. In the present study, psicose was produced stably with high productivity using the immobilized d-psicose 3-epimerase in the presence of borate.     

Catalytic removal of sulfide by an immobilized sulfide-oxidase bioreactor

A bioreactor packed with chitosan immobilized sulfide-oxidase from Streptomyces species LD048 was developed to treat a liquid stream of sulfide. The inoculation system was composed of glass with a 0.7 L working volume and enzyme activity of 2 mmol S g^?1 carrier. The sulfide removal efficiency was almost 100% when the volumetric loading was increased up to 3.9 mmol S L^?1 h^?1 at a space velocity of 18 h^?1. The maximal elimination capacity was 22.1 mmol S L^?1 h^?1 with a space velocity of 72 h^?1. When the aeration was increased from 0.05 to 0.1 L min^?1, the average removal efficiency improved from 81% to 94%. A removal efficiency of 90% was obtained after 15 days of operation with a load rate of 8.9 mmol S L^?1 h^?1 and a space velocity of 14.28 h^?1. An operational equation based on the ideal plug flow bioreactor and the Michaelis–Menten model predicted the performance of this bioreactor.     

Treatment of dye (Remazol Blue) and heavy metals using yeast cells with the purpose of managing polluted textile wastewaters

The bioaccumulation of chromium(VI), nickel(II), copper(II), and reactive dye by the yeast Rhodotorula mucilaginosa has been investigated in media containing molasses as a carbon and energy source. Optimal pH values for the yeast cells to remove the pollutants were pH 4 for copper(II) and dye, pH 6 for chromium(VI) and dye, and pH 5 for nickel(II) and dye in media containing 50 mg l^?1 heavy metal and 50 mg l^?1 Remazol Blue. The maximum dye bioaccumulation was observed within 4–6 days and uptake yields varied from 93% to 97%. The highest copper(II) removal yields measured were 30.6% for 45.4 mg l^?1 and 32.4% for 95.9 mg l^?1 initial copper(II) concentrations. The nickel(II) removal yield was 45.5% for 22.3 mg l^?1, 38.0% for 34.7 mg l^?1, and 30.3% for 62.2 mg l^?1. Higher chromium(VI) removal yields were obtained, such as 94.5% for 49.2 mg l^?1 and 87.7% for 129.2 mg l^?1 initial chromium(VI) concentration. The maximum dye and heavy metal bioaccumulation yield was investigated in media with a constant dye (approximately 50 mg l^?1) and increasing heavy metal concentration. In the medium with 48.9–98.8 mg l^?1 copper(II) and constant dye concentration, the maximum copper(II) bioaccumulation was 27.7% and 27.9% whereas the maximum dye bioaccumulation was 96.1% and 95.3%. The maximum chromium(VI) bioaccumulation in the medium with dye was 95.2% and 80.3% at 48.2 and 102.2 mg l^?1 chromium(VI) concentrations. In these media dye bioaccumulation was 76.1% and 35.1%, respectively. The highest nickel(II) removal was 6.1%, 20.3% and 16.0% in the medium with 23.8 mg l^?1 nickel(II) + 37.8 mg l^?1 dye, 38.1 mg l^?1 nickel(II) + 33.4 mg l^?1 dye and 59.0 mg l^?1 nickel(II) + 39.2 mg l^?1 dye, respectively. The maximum dye bioaccumulation yield in the media with nickel(II) was 94.1%, 78.0% and 58.7%, respectively.     

Diurnal exchanges of CO2 and CH4 across the water–atmosphere interface in a water chestnut meadow (Trapa natans L.)

CH₄ and CO₂ fluxes across the water–atmosphere interface were measured over a 24 h day–night cycle in a shallow oxbow lake colonized by the water chestnut (Trapa natans L.) (Lanca di Po, Northern Italy). Only exchanges mediated by macrophytes were measured, whilst gas ebullition was not considered in this study. Measurements were performed from 29 to 30 July 2005 with short incubations, when T. natans stands covered the whole basin surface with a mean dry biomass of 504 ± 91 g m⁻². Overall, the oxbow lake resulted net heterotrophic with plant and microbial respiration largely exceeding carbon fixation by photosynthesis. The water chestnut stand was a net sink of CO₂ during the day-light period (−60.5 ± 8.5 mmol m⁻² d⁻¹) but it was a net source at night (207.6 ± 6.1 mmol m⁻² d⁻¹), when the greatest CO₂ efflux rate was measured across the water surface (28.2 ± 2.4 mmol m⁻² h⁻¹). The highest CH₄ effluxes (6.6 ± 1.8 mmol m⁻² h⁻¹) were determined in the T. natans stand during day-time, whilst CH₄ emissions across the plant-free water surface were greatest at night (6.8 ± 2.1 mmol m⁻² h⁻¹). Therefore, we assumed that the water chestnut enhanced methane delivery to the atmosphere. On a daily basis, the oxbow lake was a net source to the atmosphere of both CO₂ (147.1 ± 10.8 mmol m⁻² d⁻¹) and CH₄ (116.3 ± 8.0 mmol m⁻² d⁻¹).     

Evaluation of zinc tolerance and accumulation potential of the coastal shrub Limoniastrum monopetalum (L.) Boiss.

The coastal shrub Limoniastrum monopetalum is capable of growth in soil containing extremely high concentrations of heavy metals. A greenhouse experiment was conducted in order to investigate the effects of a range of Zn concentrations (0–130 mmol l⁻¹) on growth and photosynthetic performance, by measuring relative growth rate, total leaf area, plant height, gas exchange, chlorophyll fluorescence parameters and photosynthetic pigment concentrations. We also determined the total zinc, nitrogen, phosphorus, sulphur, calcium, magnesium, sodium, potassium, iron and copper concentrations in the plant tissues. The study species demonstrated hypertolerance to Zn stress, since survival was recorded with leaf concentrations of up to 1700 mg Zn kg⁻¹ dry mass when treated with 130 mmol Zn l⁻¹. L. monopetalum exhibited little overall effects on photosynthetic function at Zn levels of up to 90 mmol l⁻¹. At greater external Zn concentration, plant growth was negatively affected, due in all probability to the recorded decline in net photosynthetic rate, which may be linked to the adverse effect of the metal on photosynthetic electron transport. Growth parameters were virtually unaffected by leaf tissue concentrations as high as 1400 mg Zn kg⁻¹ dry mass thus indicating that this species could play an important role in the phytoremediation of Zn-polluted areas.     

Nitrification rates of algal–bacterial biofilms in wastewater stabilization ponds under light and dark conditions

The objective of this study was to investigate nitrification rates in algal–bacterial biofilms of waste stabilization ponds (WSP) under different conditions of light, oxygen and pH. Biofilms were grown on wooden plates of 6.0 cm by 8.0 cm by 0.4 cm in a PVC tray continuously fed with synthetic wastewater with initial NH₄-N and Chemical Oxygen Demand (COD) concentrations of 40 mg l^?1 and 100 mg l^?1, respectively, under light intensity of 85–95 μE m^?2 s^?1. Batch activity tests were carried out by exposure of the plates to light conditions as above (to simulate day time), dim light of 1.8–2.2 μE m^?2 s^?1 (to simulate reduced light as in deeper locations in WSP) and dark conditions (to simulate night time). Dissolved oxygen (DO) concentration and pH were controlled. At some experiments, both parameters were kept constant, and at others they were left to vary as in WSP. Results show biofilm nitrification rates of 945–1817 mg-N m^?2 d^?1 and 1124–1615 mg-N m^?2 d^?1 for light and dark experiments. When the minimum DO was 4.1 mg l^?1, the biofilm nitrification rates under light and dark conditions did not differ significantly at 95% confidence. When the minimum DO in the dim light experiment was 3.2 mg l^?1, the nitrification rates under light and dim light conditions were 945 mg-N m^?2 d^?1 and 563 mg-N m^?2 d^?1 and these significantly differed. Further decrease of DO to 1.1 mg l^?1 under dark conditions resulted in more decrease of the nitrification rates to 156 mg-N m^?2 d^?1. It therefore seems that under these experimental conditions, biofilm nitrification rates are significantly reduced at a certain point when bulk water DO is between 3.2 mg l^?1 and 4.1 mg l^?1. As long as bulk water DO under dark is high, light is not important in influencing the process of nitrification.     

Continuous Cr(VI) removal by Scenedesmus incrassatulus in an airlift photobioreactor

Cr(VI) removal by Scenedesmus incrassatulus was characterized in a continuous culture system using a split-cylinder internal-loop airlift photobioreactor fed continuously with a synthetic effluent containing 1.0 mg Cr(VI) l^?1 at dilution rate (D) of 0.3 d^?1. At steady state, there was a small increase (6%) on the dry biomass (DB) concentration of Cr(VI)-treated cultures compared with the control culture. 1.0 mg Cr(VI) l^?1 reduced the photosynthetic pigments content and altered the cellular morphology, the gain in dry weight was not affected. At steady state, Cr(VI) removal efficiency was 43.5 ± 1.0% and Cr(VI) uptake was 1.7 ± 0.1 mg Cr(VI) g^?1 DB. The system reached a specific metal removal rate of 458 μg Cr(VI) g^?1 DB d^?1, and a volumetric removal rate of 132 μg Cr(VI) l^?1 d^?1.     

Determination of hippuric acid in human urine by ion chromatography with conductivity detection

A simple, rapid, precise and eco-friendly ion chromatography (IC) method for the determination of hippuric acid (HA) in human urine was proposed in this paper. The separation was carried out an anion exchange column with 2.0 mmol L^?1 Na₂CO₃ + 2.0 mmol L^?1 NaHCO₃ as mobile phase at the flow-rate 0.7 mL min^?1. A suppressed conductivity detector was used and the detection limit was 1.0 μg L^?1(S/N = 3) for hippuric acid. The analysis time for one run was 30 min under the optimized IC condition. The recovery of hippuric acid was 93.2–98.0% while the relative standard deviation (RSD) was 1.4–2.3% by seven measurements.     

Structure and seasonal dynamics of the protozoan community (heterotrophic flagellates,ciliates, amoeboid protozoa) in the plankton of a large river (River Danube,Hungary)

Seasonal dynamics of all major protozoan groups were investigated in the plankton of the River Danube, upstream of Budapest (Hungary), by bi-weekly sampling over a 1-year long period. Sixty-one heterotrophic flagellate, 14 naked amoeba, 50 testate amoeba, 4 heliozoan and 83 ciliate morphospecies were identified. The estimated abundance ranges of major groups throughout the year were as follows: heterotrophic flagellates, 0.27–7.8×10⁶ ind. l^?1; naked amoebae, max. 3300 ind. l^?1; testaceans, max. 1600 ind. l^?1; heliozoans, max. 8500 ind. l^?1; ciliates, 132–34,000 ind. l^?1. In terms of biovolume, heterotrophic flagellates dominated throughout the year (max. 0.58 mm³ l^?1), and ciliates only exceeded their biovolume in summer (max. 0.76 mm³ l^?1). Naked amoeba and heliozoan biovolume was about one, and testacean biovolume 1–3, orders of magnitude lower than that of ciliates. In winter, flagellates, mainly chrysomonads, had the highest biomass, whilst ciliates were dominated by peritrichs. In 2005 from April to July a long spring/summer peak occurred for all protozoan groups. Beside chrysomonads typical flagellates were choanoflagellates, bicosoecids and abundant microflagellates (large chrysomonads and Collodictyon). Most abundant ciliates were oligotrichs, while Phascolodon, Urotricha, Vorticella, haptorids, Suctoria, Climacostomum and Stokesia also contributed significantly to biovolume during rapid succession processes. In October and November a second high protozoan peak occurred, with flagellate dominance, and slightly different taxonomic composition.     

Functional consortium for hydrogen production from cellobiose: Concentration-to-extinction approach

A functional bacterial consortium that can effectively hydrolyze cellobiose and produce bio-hydrogen was isolated by a concentration-to-extinction approach. The sludge from a cattle feedlot manure composting plant was incubated with 2.5–20 g l^?1 cellobiose at 35 °C and pH 6.0. The microbial diversity of serially concentrated suspensions significantly decreased following increasing cellobiose concentration, finally leaving only two viable strains, Clostridium butyricum strain W4 and Enterococcus saccharolyticus strain. This consortium has a maximum specific hydrogen production rate of 2.19 mol H₂ mol hexose^?1 at 5 g l^?1 cellobiose. The metabolic pathways shifted from ethanol-type to acetate-butyrate type as cellobiose concentration increased from 2.5 to >7 g l^?1. The concentration-to-extinction approach is effective for isolating functional consortium from natural microflora. In this case the functional strains of interest are more tolerant to the increased loadings of substrates than the non-functional strains.     

Kinetic analysis of photosynthetic growth and photohydrogen production of two strains of Rhodobacter Capsulatus

Two mutants of Rhodobacter Capsulatus (JP91 and IR3), a photosynthetic purple non-sulfur bacterium, were grown in a batch photobioreactor under illumination with 30 mmol l⁻¹ dl-lactate and 5 mmol l⁻¹ l-glutamate as carbon and nitrogen source, respectively. Bacterial growth was measured by monitoring the increase in absorbance at 660 nm. The photosynthetic growth processes under different cultivated temperatures are well fitted by a specific logistic model to analyze the kinetics of photosynthetic growth of two strains, thus the apparent growth rates (k) of these photosynthetic bacteria, the variations of cell dry weight (CDW) as well as their relationship with temperature are obtained. In present work, k is (0.1465 ± 0.0146), (0.2266 ± 0.0207) and (0.3963 ± 0.0257) h⁻¹ for JP91 and (0.1117 ± 0.0122), (0.1218 ± 0.0133) and (0.2223 ± 0.0152) h⁻¹ for IR3 at 26, 30 and 34 °C, respectively. And the difference between CDW_max and CDW₀ is (0.8997 ± 0.0097), (0.8585 ± 0.0093) and (0.9241 ± 0.0099) g l⁻¹ for JP91 and (0.8167 ± 0.0089), (0.7878 ± 0.0086) and (0.8358 ± 0.0091) g l⁻¹ for IR3 at 26, 30 and 34 °C, respectively. Also real-time monitoring of hydrogen production rates is acquired by recording the flow rates of photohydrogen for these two strains under different temperatures. The effects of temperature on the bacteria growth, hydrogen production capability and substrate conversion efficiency are discussed based on these results. The most preferment temperature, 30 °C, showed good substrate conversion efficiency of 52.7 and 68.2% for JP91 and IR3, respectively.     

Hemicellulose sugar recovery from steam-exploded wheat straw for microbial oil production

There are currently few successful examples of using straw hemicellulose as a carbon source in the fermentation industry. In this paper, hemicellulose hydrolysates were recovered from steam-exploded wheat straw (SEWS) and used to produce microbial oil. The effects of the steam explosion treatment conditions, the elution temperature and the ratio of elution water to SEWS on sugar recovery were examined. A broth with 3.8 g l^?1 of reducing sugar and 22.3 g l^?1 of total soluble sugars was obtained with a 10-fold excess (w/w) of water at 40 °C to wash the SEWS treated under steam explosion conditions at 200 °C for 5 min. This broth was used to produce microbial oil by the oleaginous fungus Microsphaeropsis sp., which was able to secrete xylanase to degrade oligosaccharides from straw hemicellulose and accumulate microbial oil. Under optimized conditions, the oil concentration was 2.6 g l^?1. The yield of oil from sugar consumed was 0.14 g g^?1. The microbial oil produced by this research could be used as feedstock for biodiesel production because the microbial oil was primarily composed of neutral lipids. This research establishes a novel protocol for microbial oil production from straw hemicellulose.     

Isoamyl acetate synthesis in imidazolium-based ionic liquids using packed bed enzyme microreactor

The acylation of isoamyl alcohol with acetic anhydride catalyzed by immobilized Candida antarctica lipase B was studied in ionic liquids (ILs) based on quaternary imidazolium cations with alkyl, alkenyl, alkynyl, benzyl, alkoxyl or N-aminopropyl side chains. Among the tested ILs, the highest enzyme activity together with the highest isoamyl acetate yield were obtained in [C₇mmim][Tf₂N]. No loss of lipase B activity was observed during one-month incubation in this hydrophobic IL without the presence of substrates. Isoamyl acetate synthesis using [C₇mmim][Tf₂N] as solvent was further studied in a continuously operated miniaturized enzymatic packed bed reactor at various flow rates and temperatures. Up to 92% isoamyl acetate yield could be obtained within 15 min by using 0.5 M acetic anhydride and 1.5 M isoamyl alcohol inlet concentrations at 55 °C, corresponding to the volumetric productivity of 61 mmol l^?1 min^?1, which to the best of our knowledge is the highest reported so far for this reaction. No decrease in productivity was experienced during the subsequent runs of continuous microbioreactor operation performed within 14 consecutive days. The benefits of reactor miniaturization along with the green solvent application were therefore successfully exploited for the development of a sustainable flavour ester production.     

Growth and development of cotton (Gossypium hirsutum L.) in response to CO2 enrichment under two different temperature regimes

An increase in atmospheric CO₂ concentration ([CO₂]) together with other climate change factors could greatly affect agricultural productivity. Understanding the impact of the change in atmospheric [CO₂] in conjunction with the ongoing global change is crucial to prepare for mitigation and any adaptation for future agricultural production. The main goal of this project was to study the time-course pattern of cotton plant growth in response to [CO₂] and temperature to investigate the hypothesis that whether response to elevated [CO₂] would change at different temperatures. An experiment was conducted in the controlled-environment chambers of the Georgia Envirotron with two different day/night temperatures levels, e.g., 25/15 °C and 35/25 °C, and three CO₂ concentrations, e.g., 400, 600 and 800 μmol l^?1. The experimental design was completely randomized with four replicates (plastic containers) per treatment. Growth analysis was conducted at bi-weekly intervals during the growing season. In addition, leaf area, leaf dry mass, root dry mass, square dry mass, boll dry mass and total above dry mass per plant were also measured at each sampling. Plant traits, including plant height, number of leaves, number of squares and number of bolls were recorded weekly. The number of days to emergence, squaring, flowering and maturity were also observed. The results showed that by increasing [CO₂] to 600 μmol l^?1 total biomass increased at both temperature levels, but a further increase of [CO₂] up to 800 μmol l^?1 increased total biomass only at the temperature of 35/25 °C. Throughout the growing season, there was no significant effect of [CO₂] levels on LAI. Increasing temperature from 25/15 °C to 35/25 °C had a positive impact on LAI across all CO₂ levels (P < 0.05). Increasing CO₂ from 400 to 600 μmol l^?1 significantly increased the number of squares by 31.4%, but a further increase to 800 μmol l^?1 caused a 6.6% decrease (non-significant) in the number of squares. The interactive effects of [CO₂] and temperature indicated that at a higher temperature, CO₂ would be more beneficial as we proceed towards the end of the growing season. However, further studies are needed to really understand the interaction between higher [CO₂] and temperature levels and cultivar characteristics.     

Bioaugmentation of microbial communities in laboratory and pilot scale sequencing batch biofilm reactors using the TOL plasmid

The aim of this study was to investigate the effectiveness of bioaugmentation and transfer of plasmid pWWO (TOL plasmid) to mixed microbial populations in pilot and laboratory scale sequencing batch biofilm reactors (SBBRs) treating synthetic wastewater containing benzyl alcohol (BA) as a model xenobiotic. The plasmid donor was a Pseudomonas putida strain chromosomally tagged with the gene for the red fluorescent protein carrying a green fluorescent protein labeled TOL plasmid, which confers degradation capacity for several compounds including toluene and BA. In the pilot scale SBBR donor cells were disappeared 84 h after inoculation while transconjugants were not detected at all. In contrast, both donor and transconjugant cells were detected in the laboratory scale reactor where the ratio of transconjugants to donors fluctuated between 1.9 × 10^?1 and 8.9 × 10^?1 during an experimental period of 32 days. BA degradation rate was enhanced after donor inoculation from 0.98 mg BA/min prior to inoculation to 1.9 mg BA/min on the seventeenth day of operation. Survival of a bioaugmented strain, conjugative plasmid transfer and enhanced BA degradation was demonstrated in the laboratory scale SBBR but not in the pilot scale SBBR.     

Hydrolytic enzymes production by Aspergillus section Nigri in presence of butylated hydroxyanisole and propyl paraben on peanut meal extract agar

BackgroundIn the last years, food grade antioxidants are used safely as an alternative to traditional fungicides to control fungal growth in several food and agricultural products.AimsIn this work, the effect of butylated hydroxyanisole (BHA) and propyl paraben (PP) on two hydrolytic enzyme activity (β-d-glucosidase and α-d-galactosidase) by Aspergillus section Nigri species under different water activity conditions (a_W; 0.98, 0.95 and 0.93) and incubation time intervals (24, 48, 72 and 96 h) was evaluated on peanut-based medium.MethodsThe activity of two glycosidases, β-d-glucosidase and α-d-galactosidase, was assayed using as substrates 4-nitrophenyl-β-d-glucopyranosido and 4-nitrophenyl-α-d-galactopyranosido, respectively. The enzyme activity was determined by the increase in optical density at 405 nm caused by the liberation of p-nitrophenol by enzymatic hydrolysis of the substrate. Enzyme activity was expressed as micromoles of p-nitrophenol released per minute.ResultsThe major inhibition in β-d-glucosidase activity of A. carbonarius and A. niger was found with 20 mmol l⁻¹ of BHA or PP at 0.98 and 0.95 a_W, respectively, whereas for α-d-galactosidase activity a significant decrease in enzyme activity with respect to control was observed in A. carbonarius among 5 to 20 mmol l⁻¹ of BHA or PP in all conditions assayed. Regarding A. niger, the highest percentages of enzyme inhibition activity were found with 20 mmol l⁻¹ of BHA or PP at 0.95 a_W and 96 h.ConclusionsThe results of this work provide information about the capacity of BHA and PP to inhibit in vitro conditions two of the most important hydrolytic enzymes produced by A. carbonarius and A. niger species.     

Production of a new exopolysaccharide (EPS) by Pseudomonas oleovorans NRRL B-14682 grown on glycerol

Pure glycerol and glycerol-rich product (GRP) obtained from the biodiesel industries were used as carbon source for the production of a new extracellular polysaccharide (EPS) by Pseudomonas oleovorans NRRL B-14682. The influence of temperature (20–40 °C) and pH (6.0–8.0) was studied. A temperature of 30 °C and pH control at 6.8 gave the maximum cell growth and EPS production. The culture attained a maximum cell dry weight (CDW) of 9.55 g l⁻¹ and an EPS concentration of 11.82 g l⁻¹ when cultivated with pure glycerol. GRP was a suitable carbon source, as shown by the slightly higher EPS concentration (12.18 g l⁻¹). The EPS productivity obtained with GRP (3.85 g l⁻¹ d⁻¹) was almost twice that obtained with pure glycerol (2.00 g l⁻¹ d⁻¹). Also, the yield on glycerol was higher for the cultivation with GRP (0.36 g g⁻¹) than for pure glycerol (0.28 g g⁻¹). The EPS was a high molecular weight heteropolysaccharide, composed by neutral sugars (37–80 wt% galactose, 2–30 wt% glucose, 0.5–25 wt% mannose and 0.5–20 wt% rhamnose) and containing acyl group substituents (pyruvil, acetyl and succinyl were identified). The EPS forms highly viscous aqueous dispersions with many potential commercial applications.     

Improved β-carotene production of Rhodotorula glutinis in fermented radish brine by continuous cultivation

Fermentation kinetics of growth and β-carotene production by Rhodotorula glutinis DM28 in batch and continuous cultures using fermented radish brine, a waste generated from fermented vegetable industry, as a cultivation medium were investigated. The suitable brine concentration for β-carotene production by R. glutinis DM28 was 30 g l^?1. Its growth and β-carotene production obtained by batch culture in shake flasks were 2.2 g l^?1 and 87 μg l^?1, respectively, while, in a bioreactor were 2.6 g l^?1 and 186 μg l^?1, respectively. Furthermore, its maximum growth rate and β-carotene productivity in continuous culture obtained at the dilution rate of 0.24 h^?1 were 0.3 g l^?1 h^?1 and 19 μg l^?1 h^?1, respectively, which were significantly higher than those in the batch. Therefore, improved growth rate and β-carotene productivity of R. glutinis in fermented radish brine could be accomplished by continuous cultivation.     

Immune responses,ROS generation and the haemocyte damage of scallop Chlamys farreri exposed to Aroclor 1254

The toxic effects of Aroclor 1254 (0.05, 0.5, 5 and 50 μg l^?1) on scallop (Chlamys farreri) immune system in vivo were studied. The results showed that Aroclor 1254 had significant toxic effect on the parameters tested in this paper (P < 0.05). The total number of haemocytes, the proportion of granulocytes, phagocytosis in all groups as well as the lysosomal membrane stability (LMS) in 5, 50 μg l^?1 and bacteriolytic activity 0.5, 5, 50 μg l^?1 treatments decreased significantly, while the proportion of hyalinocytes and the production of O₂^- in all treatments remarkably increased during the sampling time and tended to be stable gradually after 6–15 d. The bacteriolytic activity in 0.05 μg l^?1 treatments, LMS in 0.05, 0.5 μg l^?1 groups and the DNA damage (comet ratios and arbitrary values) in all treatments increased at the beginning of exposure and reached their peaks on day 1, day 1, day 6 and day 3, following that they all decreased gradually and became stable after 9–15 d. When the indices reached stability, except for DNA damage was higher than controls, the others were all significantly lower than those of controls (P < 0.05). Thus, Aroclor 1254 has evident toxic effects on scallop immune system, which supports the view that a relationship exists between pollution and immunomodulation in aquatic organisms. Also it supports the speculation that the PCBs pollution is one of the important reasons of the mass mortality of the C. farreri.