Modeling of <Emphasis Type="Italic">Fusarium redolens</Emphasis> Dzf2 mycelial growth kinetics and optimal fed-batch fermentation for beauvericin production

Beauvericin (BEA) is a cyclic hexadepsipeptide mycotoxin with notable phytotoxic and insecticidal activities. Fusarium redolens Dzf2 is a highly BEA-producing fungus isolated from a medicinal plant. The aim of the current study was to develop a simple and valid kinetic model for F. redolens Dzf2 mycelial growth and the optimal fed-batch operation for efficient BEA production. A modified Monod model with substrate (glucose) and product (BEA) inhibition was constructed based on the culture characteristics of F. redolens Dzf2 mycelia in a liquid medium. Model parameters were derived by simulation of the experimental data from batch culture. The model fitted closely with the experimental data over 20–50 g l⁻¹ glucose concentration range in batch fermentation. The kinetic model together with the stoichiometric relationships for biomass, substrate and product was applied to predict the optimal feeding scheme for fed-batch fermentation, leading to 54% higher BEA yield (299 mg l⁻¹) than in the batch culture (194 mg l⁻¹). The modified Monod model incorporating substrate and product inhibition was proven adequate for describing the growth kinetics of F. redolens Dzf2 mycelial culture at suitable but not excessive initial glucose levels in batch and fed-batch cultures.     

Optimization of a liquid medium for beauvericin production in <Emphasis Type="Italic">Fusarium redolens</Emphasis> Dzf2 mycelial culture

Beauvericin (BEA) is a proven and potent antibiotic compound useful for bio-control and a potential antifungal and anticancer agent for human. This study was to evaluate and optimize the nutrient medium for BEA production in mycelial liquid culture of a high BEA-producing fungus Fusarium redolens Dzf2 isolated from a medicinal plant. Among various organic and inorganic carbon and nitrogen sources, glucose and peptone were found the most favorable for the F. redolens Dzf2 mycelial growth and BEA production. Through a Plackett-Burman screening test on a basal medium, glucose, peptone, and medium pH were identified as the significant factors for mycelial growth and BEA production. These factors were optimized through central composite design of experiments and response surface methodology, as 49.0 g/L glucose, 13.0 g/L peptone and pH 6.6, yielding 198 mg/L BEA (versus 156 mg/L in the basal medium). The BEA yield was further increased to 234 mg/L by feeding 10 g/L glucose to the culture during exponential phase. The results show that F. redolens Dzf2 mycelial fermentation is a feasible and promising process for production of BEA.     

Enhancement of diepoxin ζ production with in situ resin adsorption in mycelial liquid culture of the endophytic fungus <Emphasis Type="Italic">Berkleasmium</Emphasis> sp. Dzf12 from <Emphasis Type="Italic">Dioscorea zingiberensis</Emphasis>

Berkleasmium sp. Dzf12, an endophytic fungus from Dioscorea zingiberensis, is a high producer of the spirobisnaphthalene diepoxin ζ. However, diepoxin ζ produced by Berkleasmium sp. Dzf12 was retained as both the intracellular and extracellular product. This study was to evaluate an in situ resin adsorption for enhancement of diepoxin ζ production in mycelial liquid culture of Berkleasmium sp. Dzf12. Diepoxin ζ production was most effectively enhanced by macroporous resin AB-8 among five test resins. The highest diepoxin ζ yield reached 448.6 mg l⁻¹ that was 1.4 fold of the control (329.7 mg l⁻¹), when 1.5 g of resin AB-8 was added to 30 ml medium in each flask on day 11 of culture and in a period of 40 h for adsorption. The results show that in situ resin adsorption is an effective strategy for enhancing diepoxin ζ production and also facilitating its recovery in mycelial liquid culture of Berkleasmium sp. Dzf12.     

Improved accumulation of phenylethanoid glycosides by precursor feeding to suspension culture of Cistanche salsa

Effects of some precursors on phenylethanoid glycosides (PeGs) accumulation in Cistanche salsa cell suspension cultures were investigated. Precursors such as tyrosine, phenylalanine, caffeic acid and cucumber juice at proper concentrations could increase the total accumulation of PeGs (echinacoside, acteoside, 2′-acetylacteoside) by 50%, 12%, 12% and 23%, respectively. Under the combined feeding of precursors at proper concentrations, the total production of PeGs in bio-staged culture reached the highest amount of 1358.1 mg l⁻¹ (640.8 mg echinacoside l⁻¹, 689.4 mg acteoside l⁻¹ and 54.9 mg 2′-acetylacteoside l⁻¹), which was about two-fold of that in the control. This study showed promise for obtaining large-scale production of active ingredients in plant cells by the solid–liquid two step culture (SLTSC) technique and also provided for the first time an example for producing PeGs by C. salsa cell culture. The improved production of PeGs was higher than that in previous reports on PeG production by Cistanche deserticola cell culture fed with precursors.     

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.     

Protocorm culture of Dendrobium candidum in balloon type bubble bioreactors

Protocorm cultures of Dendrobium candidum were established in balloon type bubble bioreactors using Murashige and Skoog (MS) medium with 0.5 mg l⁻¹ α-naphthaleneacetic acid (NAA), 2.5% (w/v) sucrose, 5:25 mM NH₄:NO₃ and 1% (v/v) banana homogenate for the production of biomass and bioactive compounds. In 3 l bioreactor containing 2 l medium, a maximum protocorm biomass (21.0 g l⁻¹ dry biomass) and also optimum quantities of total polysaccharides (389.3 mg g⁻¹ DW), coumarins (18.0 mg g⁻¹ DW), polyphenolics (11.9 mg g⁻¹ DW), and flavonoids (4.5 mg g⁻¹ DW) were achieved after 7 weeks of culture. Based on these studies, 5 and 10 l bioreactor cultures were established to harvest 80 g and 160 g dry biomass. In 10 l bioreactors, the protocorms grown were accumulated with optimal levels of polysaccharides (424.1 mg g⁻¹ DW), coumarins (15.8 mg g⁻¹ DW), polyphenols (9.03 mg g⁻¹ DW) and flavonoids (4.7 mg g⁻¹ DW). The bioreactor technology developed here will be useful for the production of important bioactive compounds from D. candidum.     

Improvement of epothilone B production by in situ removal of ammonium using cation exchange resin in Sorangium cellulosum culture

A cation exchange resin was added at different stages in the growth of Sorangium cellulosum cultures to remove excess ammonium, which has a negative influence on the production of the anticancer agent, epothilone. When 8 g L⁻¹ of cation exchange resin were added at the mid-death phase, the ammonium removal reached 83% and the maximum production of epothilone was 14.3 mg L⁻¹, which was 2.6 times greater than that of the control culture.     

Assessment of Lemna gibba L. (duckweed) as a potential ecological indicator for contaminated aquatic ecosystem by boron mine effluent

Duckweeds, as a group, are important early warning indicators for the assessment of contaminated ecosystems due to their propensity to accumulate pollutants. In the present study, we investigated the potential use of Lemna gibba L. (Lemnaceae) as an ecological indicator for boron (B) mine effluent containing B concentration above 10 mg l⁻¹. For this purpose, L. gibba fronds were grown for 7 days in simulated water contaminated with B mine effluent. The important note is that this study was carried out in Kırka (Eskişehir, Turkey) B reserve area, which is the largest borax reserve in all over the world, under natural climatic conditions in the field. The results demonstrated that accumulations of B by L. gibba gradually increased based on the initial B concentrations (10, 25, 50, 100, and 150 mg l⁻¹) of the mine effluent. B concentration in the dry weight of the plant reached 639 mg kg⁻¹ when the minimum initial dosage (10 mg l⁻¹) was applied and 2711 mg kg⁻¹ when the maximum initial dosage (150 mg l⁻¹) was applied during the study. However, significant reductions in their relative growth rates occurred in 50, 100 and 150 mg l⁻¹ initial B concentrations. Results suggest that 25 mg l⁻¹ B concentration in water seemed to be a sensitive endpoint for L. gibba that could be used as a critical bioindicator level of B contaminated water. Following our data, we also constructed a simple growth model under the climatic conditions in this region of Turkey, but in instructive as a worldwide model. L. gibba is, therefore, suggested to be able to use as both an indicator and a phytoremediation tool because of its high accumulation capacity for B contaminated water.     

Mathematical analysis of trickling filter response to pentachlorophenol shock load

The response of a laboratory trickling filter to a step increase in pentachlorophenol (PCP) feed concentration was analyzed using continuous stirred tank (CSTR) and plug flow reactor (PFR) models. The CSTR model provided a slightly better fit to experimental data than the plug flow model when specific growth rate, μ, and PCP-degrading biomass concentration before the shock load, X₀, were variable parameters but was clearly superior when the mean residence time, τ, was added as a third parameter. The three-parameter CSTR model accurately represented six of seven concentration response curves corresponding to step increases in PCP feed concentration of 12–165 mg l⁻¹ and 20–150 mg l⁻¹. The continuing improvement in system response to repetitive 20–150 mg l⁻¹ shock loads was reflected by a monotonic increase in the optimal estimates of initial rate of biomass production.     

Production of an anti-MUC1 C595 dbFv antibody fragment in recombinant Escherichia coli

The production of C595 diabody fragment (dbFv) in Escherichia coli (E. coli) HB2151 clone has been explored. The comparison of fermentation processes mode demonstrated that a higher biomass inoculum operation enhanced C595 dbFv production. It was demonstrated that a concentration of 12.1 mg l⁻¹ broth of dbFv and a cell concentration of 23.6 g l⁻¹ broth were achieved at the end of 75 l fermentation.     

Production of polysaccharide–peptide complexes by submerged mycelial culture of an entomopathogenic fungus Cordyceps sphecocephala

The effects of medium components and environmental factors on the production of mycelial biomass and polysaccharide–peptide complexes (exobiopolymers) by Cordyceps sphecocephala J-201 were investigated in submerged cultures. The optimal temperature and initial pH for the production of both mycelial biomass and exobiopolymers in flask cultures were found to be 25 °C and pH 4–5, respectively. The optimal combination of the media constituents was as follows (g l⁻¹): sucrose 40, yeast extract 6, polypepton 2, KH₂PO₄ 0.46, K₂HPO₄ 1, and MgSO₄·7H₂O 0.5. The results of bioreactor culture revealed that the maximum concentration of mycelial biomass (28.2 g l⁻¹) was obtained at an agitation speed of 300 rpm and at an aeration rate of 2 vvm, whereas maximum exobiopolymer production (2.5 g l⁻¹) was achieved at a milder agitation speed (150 rpm). There was a significant variance in mycelial morphology between different aeration conditions. Looser mycelial pellets were developed, and their size and hairiness increased as the aeration rate increased from 0.5 to 2.0 vvm, resulting in enhanced exobiopolymer production. The apparent viscosities of fermentation broth increased rapidly towards the end of fermentations at the conditions of high aeration rate and agitation speed, which were mainly due to high amount of mycelial biomass rather than exobiopolymers at the later stages of fermentation. The three different exobiopolymers (FR-I, -II, and -III) were fractionated by a gel filtration chromatography on Sepharose CL-6B. The carbohydrate and protein contents in each fraction were significantly different and the molecular weights of FR-I, FR-II, and FR-III were determined to be 1831, 27, and 2.2 kDa, respectively. The compositional analysis revealed that the three fractions of crude exobiopolymers consisted of acidic and nonpolar amino acids, such as aspartic acid, glutamic acid, glycine, and valine in protein moiety, and of mainly mannose and galactose in sugar moiety.     

Multiple regeneration pathways in Spathoglottis plicata Blume — A study in vitro

Asymbiotic germination of immature seeds (embryos), and mature seeds and micropropagation of Spathoglottis plicata were described. Effects of three nutrition media namely, Murashige & Skoog (MS); Phytamax (PM); and Phyto-Technology orchid seed sowing medium (P₇₂₃), two carbon sources such as glucose and sucrose at 2–3% (w/v), two plant growth regulators such as 6-benzylaminopurine (BAP; 0.5–3.0 mg l^− 1) and α-naphthalene acetic acid (NAA; 0.5–2.0 mg l^− 1) and peptone (2.0 g l^− 1) were examined on seed germination, early protocorm development and micropropagation. The maximum germination of mature seeds (95%) was recorded in PM medium supplemented with 2% (w/v) sucrose + 2.0 g l^− 1 peptone. For germination of embryos P₇₂₃ medium supplemented with 1.0 mg l^− 1 BAP proved best. Multiple shoot buds or protocorm-like bodies (PLBs) were produced from stem segments of in vitro raised seedlings. Both direct organogenesis and embryogenesis were observed and the morphogenetic response was initiated by different concentrations and combinations of PGRs. The optimum PGR combination for maximal PLB regeneration was 1.0 mg l^− 1 NAA + 2.5 mg l^− 1 BAP, while 1.0 mg l^− 1 NAA + 1.0 mg l^− 1 BAP for shoot bud development. Strong and stout root system was induced in half strength PM medium supplemented with 0.5 mg l^− 1 IAA. The well-rooted plantlets were transferred to pots containing a potting mixture composed of saw dust, coconut coir, humus, and coal pieces at 1:1:1:2 (w/w) with 80% survival in outside environment and flowered after two years of transfer.     

Improved production of lycopene and β-carotene by Blakeslea trispora with oxygen-vectors

Lycopene and β-carotene production were increased when oxygen-vectors, n-hexane and n-dodecane, were added to cultures of Blakeslea trispora because of the enhanced dissolved oxygen concentrations. With 1% (v/v) n-hexane or n-dodecane added in the medium, lycopene production was 51% or 78% higher and β-carotene production was 44% or 65% higher than that of the control, respectively. The highest lycopene and β-carotene production, 533 mg l⁻¹and 596 mg l⁻¹, were obtained when 1% (v/v) n-dodecane and 0.1% (w/v) Span 20 were added together, which were 2.1-fold and 1.8-fold of the control, respectively.     

Influence on dithiolopyrrolone antibiotic production by organic acids in Saccharothrix algeriensis NRRL B-24137

The influence of organic acids on growth and dithiolopyrrolone antibiotic production by Saccharothrix algeriensis NRRL B-24137 was studied. The production of dithiolopyrrolones depends upon the nature and concentration of the organic acids in the culture medium. Study of the nature of organic acids showed that the most effective organic acids for thiolutin specific production were maleic, 4-hydroxybenzoic, benzentetracarboxylic, pantothenic, pivalic and pyruvic acids (which yielded almost five-fold over the starting medium) and pimelic acid (more than three-fold). 4-Bromobenzoic acid showed the best production of senecioyl-pyrrothine (59 mg g⁻¹ DCW). Tiglic acid showed the best production of tigloyl-pyrrothine (22 mg g⁻¹ DCW). The highest yield of isobutyryl-pyrrothine (7.6 mg g⁻¹ DCW) was observed in the presence of crotonic acid. Sorbic acid yielded the best production of butanoyl-pyrrothine (26 mg g⁻¹ DCW). Methacrylic, butyric, pyruvic and 4-bromobenzoic acids also exhibited the best production of butanoyl-pyrrothine (27–11-fold).Study of organic acid concentration showed that among the selected organic acids, pimelic acid yielded the highest specific production of thiolutin (91 mg g⁻¹ DCW) at 7.5 mM; and senecioyl-pyrrothine (11 mg g⁻¹ DCW), tigloyl-pyrrothine (9 mg g⁻¹ DCW) and butanoyl-pyrrothine (3.5 mg g⁻¹ DCW) at 5 mM. Pyruvic acid at 1.25 mM enhanced the production of senecioyl-pyrrothine (4.3 mg g⁻¹ DCW). The maximum production of tigloyl-pyrrothine (18.6 mg g⁻¹ DCW) was observed in the presence of tiglic acid at 2.5 mM. Maximum production of isobutyryl-pyrrothine was observed in the presence of 7.5 mM tiglic acid. In addition, methacrylic acid (at 5 mM) and butyric acid (at 2.5 mM) enhanced the production of butanoyl-pyrrothine (26 and 20 times, respectively).The above results can be employed in the optimisation of the culture medium for the production of dithiolopyrrolone in higher quantities.     

Chromate reduction by resting cells of Achromobacter sp. Ch-1 under aerobic conditions

Chromate reduction was carried out by resting cells of Achromobacter sp. Ch-1 with lactate as electron donor under aerobic conditions. The reduction activity of the samples supplemented with lactate was two times as those without lactate. The reduction rate was influenced by initial pH and lactate concentration. Under the optimal conditions, pH 9.0 and 4000 mg l⁻¹ lactate supplement, reduction rate was 5.45 mg l⁻¹ min⁻¹. The reduction rate decreased with increasing of Cr(VI) concentrations and increased with cell densities proportionally. The maximum reduction limit of Ch-1 cells was obtained at 2107 mg l⁻¹ of Cr(VI).     

Isolation of hexavalent chromium resistant bacteria from industrial saline effluents and their ability of bioaccumulation

The mixed cultures has been isolated from industrial saline wastewater contaminated with chromium(VI), using enrichment in the presence of 50 mg l⁻¹ chromium(VI) and 4% (w/v) NaCl at pH 8. In this study, the molasses (M) medium was selected a suitable medium for the effective chromium bioaccumulation by the mixed cultures. Eleven pure isolates obtained from mixed cultures and some of them showed high bioaccumulation in the M media containing about 100 mg l⁻¹ chromium(VI) and 4% NaCl. The strain 8 (99.3%) and 10 (99.1%) were able to bioaccumulate more efficient than the mixed culture (98.9%) in this media. But the highest specific Cr uptake was obtained by the mixed cultures followed by strain 8 and 10 with 56.71, 33.14 and 21.7 mg g⁻¹, respectively. Bioaccumulation of chromium(VI) ions by the strain 8 growing in the media with chromium(VI) and NaCl was studied in a batch system as a function of initial chromium(VI) (86.6–547.6 mg l⁻¹) and NaCl (0, 2, 4, 6% w/v) concentrations. During all the experiments, the uptake yield of the strain 8 was highly affected from NaCl concentrations in the medium at high initial chromium(VI) concentrations. But at low chromium(VI) concentration, strain 8 was not affected from NaCl concentrations in the medium. The maximum uptake yield were obtained in the M media with 2% NaCl as 98.8% for 110.0 mg l⁻¹, 98.6% for 217.1 mg l⁻¹, 98.6% for 381.7 mg l⁻¹ and 98.2% for 547.6 mg l⁻¹ initial chromium(VI) concentrations. The strain 8 tolerated a 6% (w/v) NaCl concentration was able to bioaccumulate more than 95% of the applied chromium(VI) at the 97.6–224.4 mg l⁻¹ initial chromium(VI) concentrations. The results presented in this paper was shown that these pure and mixed cultures might be of use for the bioaccumulation of chromium(VI) from saline wastewater.     

Treatment of dye-rich wastewater by an immobilized thermophilic cyanobacterial strain: Phormidium sp.

The removal of Remazol Blue and Reactive Black B by the immobilized thermophilic cyanobacterial strain Phormidium sp. was investigated under thermophilic conditions in a batch system, in order to determine the optimal conditions required for the highest dye removal. In the experiments, performed at pH 8.5, with different initial dye concentrations between 9.1 mg l⁻¹ and 82.1 mg l⁻¹ and at 45 °C, calcium alginate immobilized Phormidium sp. showed high dye decolorization, with maximum uptake yields ranging from 50% to 88% at all dye concentrations tested. When the effects of high dye concentrations on dye removal were investigated, the highest uptake yield in the beads was 50.3% for 82.1 mg l⁻¹ Remazol Blue and 60.0% for 79.5 mg l⁻¹ Reactive Black B. The highest color removal was detected at 45 °C and 50 °C incubation temperatures for all dye concentrations. As the temperature decreased, the removal yield of immobilized Phormidium sp. also decreased. At about 75 mg l⁻¹ initial dye concentrations, the highest specific dye uptake measured was 41.29–41.17 mg g⁻¹ for Remazol Blue and 47.69–43.82 mg g⁻¹ for Reactive Black B at 45 °C and 50 °C incubation temperatures, respectively, after 8 days incubation.     

Promotion of Salvia miltiorrhiza hairy root growth and tanshinone production by polysaccharide–protein fractions of plant growth-promoting rhizobacterium Bacillus cereus

This study was to examine the effects of polysaccharides from a plant growth-promoting rhizobacterium (PGPR) Bacillus cereus on the growth and tanshinone production of Salvia miltiorrhiza hairy roots. A polysaccharide fraction designated BPS was isolated from the hot water extract of B. cereus cells by ethanol precipitation. BPS applied to the root culture at 100–400 mg l⁻¹ a few days before the stationary growth phase stimulated the tanshinone accumulation of roots by about 7-fold (1.59 mg g⁻¹ versus 0.19 mg g⁻¹) and also notably promoted the root growth (15% increase in biomass). BPS was a polysaccharide–protein complex containing about 27% protein, which is essential for root growth promotion. BPS was separated by ultrafiltration into two molecular weight (MW) fractions, of which the high MW fraction (∼35.8 kDa) with higher protein content (∼31%) promoted the root growth while the lower MW fraction with lower protein content (∼17%) suppressed the growth. The results suggest that the polysaccharide portion of BPS was responsible for stimulating the tanshinone accumulation while the protein portion was responsible for promoting the hairy root growth. Polysaccharides from PGPR are potential sources of active elicitors and growth-promoting agents for plant roots in culture.     

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.     

Nitrogen transformation in the hybrid bioreactor landfill

The hybrid bioreactor landfill was promising in solid waste management. In the work, the nitrogen removal and nitrogen transformation in hybrid bioreactor landfill with sequencing of facultative anaerobic and aerobic conditions was explored. The result showed that the combination of facultative anaerobic and aerobic conditions in the hybrid bioreactor landfill was indeed effective in eliminating ammonia both from the leachate and the refuse thoroughly. About 72% of nitrogen was reduced from the landfilled fresh refuse through the operation of 357 days. At the end of the experiment, the concentrations of COD, ammonia, nitrate and TN in the leachate decreased to 399.2 mg l^?1, 20.6 mg N l^?1, 3.7 mg N l^?1 and 25.3 mg N l^?1, respectively.