Production of the antitumoral retamycin during continuous fermentations of Streptomyces olindensis

Continuous fermentations were performed in order to correlate the production of retamycin, an anthracycline antibiotic produced by Streptomyces olindensis in submerged cultures, with the dilution rate. Maximum retamycin production was achieved at a dilution rate of 0.05 h⁻¹ (D=μ_x=0.05 h⁻¹), while higher dilution rates caused a decrease in antibiotic production, which ceased completely at a dilution rate of 0.30 h⁻¹. Otherwise, biomass productivity was favoured by high dilution rates, achieving a maximum at D=0.25 h⁻¹, whereas retamycin productivity reached a maximum at D=0.05 h⁻¹. Dilution rate influenced morphology, which was assessed by image analysis. The percentage of clumps decreased with an increase in dilution rate, with a correspondent increase in pellet percentage.     

Bench-scale fermentation of Trichoderma viride on wastewater sludge: Rheology, lytic enzymes and biocontrol activity

Conidiation and lytic enzyme production by Trichoderma viride at different solids concentration of pre-treated municipal wastewater sludge was examined in a 15-L fermenter. The maximum conidia concentration (5.94 × 10⁷ CFU mL⁻¹ at 96 h) was obtained at 30 g L⁻¹ suspended solids. The maximum lytic enzyme activities were achieved around 12–30 h of fermentation. Bioassay against a fungal phytopathogen, Fusarium sp. showed maximum activity in the sample drawn around 96 h of fermentation at 30 g L⁻¹ suspended solids concentration. Entomotoxicity against spruce budworm larvae showed maximum value ≈17290 SBU μL⁻¹ at 30 g L⁻¹ suspended solids concentration at the end of fermentation (96 h). Plant bioassay showed dual action of T. viride, i.e., disease prevention and growth promotion. The rheological analyses of fermentation sludges showed the pseudoplastic behaviour. In order to maintain required dissolved oxygen concentration ≥30%, the agitation and aeration requirements significantly increased at 35 g L⁻¹ compared to 30 and 25 g L⁻¹. The oxygen uptake rate and volumetric oxygen mass transfer coefficient, k_La at 35 g L⁻¹ did not increase in comparison to 30 g L⁻¹ due to rheological complexity of the broth during fermentation. Thus, the successful fermentation operation of the biocontrol fungus T. viride is a rational indication of its potential for mass-scale production for agriculture and forest sector as a biocontrol agent.     

Production of cyclodextrin by poly-lysine fused Bacillus macerans cyclodextrin glycosyltransferase immobilized on cation exchanger

Bacillus macerans cyclodextrin glycosyltransferase (CGTase) fused with 10 lysine residues at its C-terminus (CGTK10ase) was immobilized onto a cation exchanger by ionic interaction and used to produce -cyclodextrin (CD) from soluble starch. Poly-lysine fused immobilization increased the V_m of the immobilized CGTase by 40% without a change in K_m. The activation energies of thermal deactivation (E_a) were 41.4, 28.1, and 25.9 kcal mol⁻¹, respectively, for soluble wild-type (WT) CGTase, soluble CGTK10ase, and immobilized CGTK10ase, suggesting destabilization of CGTase by poly-lysine fusion and immobilization onto a cation exchanger. Maximum -CD productivity of 539.4 g l⁻¹ h⁻¹ was obtained with 2% soluble starch solution which was constantly fed at a flow rate of 4.0 ml min⁻¹ (D = 240 h⁻¹) in a continuous operation mode of a packed-bed reactor. The operational half-life of the packed-bed enzyme reactor was estimated 12 days at 25 °C and pH 6.0.     

Production and purification of a novel thermostable phytase by Pichia pastoris FPHY34

A genetically engineered Pichia pastoris FPHY34 strain containing a 1.3 kb thermostable phytase gene (fphy) evolved by DNA shuffling was constructed and screened. Expression and purification conditions for the recombinant phytase were developed in this study. The effect of Pi on recombinant phytase expression and cell growth of P. pastoris FPHY34 was tested in shake flask culture. Optimization of carbon sources for cell growth and methanol feeding strategies for phytase expression in P. pastoris FPHY34 was carried out in a 50-L fermenter by fed-batch fermentation. The purification of phytase was investigated by micro-filtration and ultra-filtration followed by desalting, ion-exchange chromatography, and gel filtration in the ÄKTA system. It showed that the optimum inorganic phosphorus is 13.6 g L⁻¹ and that glucose can be used as a substrate for P. pastoris cell growth instead of glycerol; the biomass yield of glycerol (Y_X/S) is slightly higher than that of glucose. Different profiles of lag phase and respiratory quotient (RQ) displayed between glucose and glycerol as the sole carbon source. The maximum phytase activity in per millimetre reached 2508 U mL⁻¹ at a methanol feed rate of 3.0 mL L⁻¹ h⁻¹ after 80 h period of induction. A purification factor of 41.1 with a 32% yield was achieved after chromatographic purification. The specific enzyme activity was 80 U mg⁻¹ and 3281 U mg⁻¹ in that supernatant fraction and after gel filtration purification, respectively. The strain P. pastoris FPHY34 showed a promising application in phytase industrial production.     

Immobilization of Acidithiobacillus ferrooxidans by a PVA–boric acid method for ferrous sulphate oxidation

Acidithiobacillus ferrooxidans was immobilized in poly(vinyl alcohol) (PVA) by a PVA–boric acid method, and spherical beads of uniform size were produced. Biooxidation of ferrous iron by immobilized cells was investigated in repeated batch culture and continuous operation in a laboratory scale packed-bed bioreactor. During repeated batch culture, the cell-immobilized gels were stable and showed high constant iron-oxidizing activity. In continuous operation in a packed-bed bioreactor, biooxidation of ferrous iron fits a plug-flow reaction model well. A maximum Fe²⁺ oxidation rate of 1.89 g l⁻¹ h⁻¹ was achieved at the dilution rate of 0.38 h⁻¹ or higher, while no obvious precipitate was detected in the bioreactor.     

Batch and continuous fermentation of succinic acid from wood hydrolysate by Mannheimia succiniciproducens MBEL55E

Batch and continuous cultures of Mannheimia succiniciproducens MBEL55E were carried out in a complex medium containing a NaOH-treated wood hydrolysate for the production of succinic acid. The wood hydrolysate based medium was treated with NaOH before sterilization to reduce the formation of inhibitory compounds. M. succiniciproducens MBEL55E utilized xylose as well as glucose in the wood hydrolysate based medium as a carbon source for the succinic acid production. In batch cultures, the final succinic acid concentration of 11.73 g l⁻¹ was obtained from the pre-treated wood hydrolysate based medium, resulting in a succinic acid yield of 56% and a succinic acid productivity of 1.17 g l⁻¹ h⁻¹, while the corresponding continuous cultures gave the succinic acid yield and productivity of 55% and 3.19 g l⁻¹ h⁻¹, respectively. These results suggest that succinic acid can be produced economically and efficiently by the fermentation of M. succiniciproducens MBEL55E from an inexpensive biomass-based wood hydrolysate.     

Enhancement of growth and gymnodimine production by the marine dinoflagellate, Karenia selliformis

Because of its novel bioactive properties the production of gymnodimine for use as a pharmaceutical precursor has aroused interest. The dinoflagellate, Karenia selliformis produces gymnodimine when grown in bulk culture using GP + selenium medium but the growth rates (μ) and levels of gymnodimine are low (μ, 0.05 days⁻¹; gymnodimine 250 μg L⁻¹ max). We describe the effects of organic acid additions (acetate, glycolate, alanine and glutamate additions and combinations of these) in enhancing growth and gymnodimine production in axenic cultures. The most effective organic acid combinations in decreasing order were: glycolate/alanine > acetate > glycolate. Glycolate/alanine optimised gymnodimine production by prolonging growth (maximum cell yield, 1.76 × 10⁵ cells mL⁻¹; gymnodimine, 1260 μg L⁻¹; growth rate (μ), 0.2 days⁻¹) compared to the control (growth maximum cell yield, 7.8 × 10⁴ cells mL⁻¹; gymnodimine, 780 μg L⁻¹; μ, 0.17 days⁻¹). Acetate enhanced gymnodimine by stimulating growth rate (μ, 0.23 days⁻¹) and the large concentration of gymnodimine per cell (16 pg cell⁻¹ cf. 9.8 pg cell⁻¹ for the control) suggests a role for this compound in gymnodimine biosynthesis. Amending culture media with Mn²⁺ additions resulted in slightly decreased growth in control cultures and increased the gymnodimine while in glycolate/alanine cultures growth was stimulated but gymnodimine production decreased. The results suggest that the organic acid can enhance gymnodimine production by either enhancing growth maximum or the biosynthetic pathway.     

Continuous production of lactic acid from whey permeate by Lactobacillus helveticus in two chemostats in series

The effect of dilution rate on the production of lactic acid from whey permeate by Lactobacillus helveticus has been investigated. In the first chemostat of a two-stage system, total conversion (98.1%) and maximum lactic acid concentration (43.7 g l⁻¹) were obtained at a dilution rate (D_Itot) of 0.06 h⁻¹. Maximum volumetric productivities of lactic acid (8.27 g l⁻¹ h⁻¹) and biomass (1.90 g l⁻¹ h⁻¹) occurred at D_Itot of 0.40 h⁻¹. The fraction of -lactate in the product was found to increase with dilution rate and reached a maximum of 66% at the same dilution rate. The maximum specific growth rate (μ_max) on this medium was 0.7 h⁻¹. A Y_ATP (max) value of 22.4 g dry weight (mol ATP)⁻¹ and a maintenance coefficient of 8.0 mmol ATP (g dry weight h)⁻¹ were determined. The second stage, in series with the first, confirmed these results and further showed that the total residence time could be reduced by 50%, compared with a single chemostat for the same nearly complete level of substrate conversion.     

Continuous production of green cells of Haematococcus pluvialis: Modeling of the irradiance effect

This paper presents a model for the continuous production of green cells of the microalga Haematococcus pluvialis, in both indoor and outdoor conditions. To develop this model, the influence of irradiance and dilution rate on the performance of continuous cultures of H. pluvialis was studied in the laboratory but simulating outdoor conditions. Characterization of the cultures included biomass productivity, fluorescence of chlorophylls, pigment content, elemental composition of the biomass, cell density, cell size, homogeneity and nitrate consumption rate. Results showed that the optimal dilution rate was 0.04 h⁻¹, and that higher external irradiance resulted in higher biomass productivity in all cases, with a maximum value of 0.58 g L⁻¹day⁻¹. Continuous cultures were stable for more than 3 months, in spite of photoinhibition at noon, producing homogeneous biomass with a stable biochemical composition and cell morphology at each steady state. Astaxanthin accumulation was not observed in spite of the high levels of irradiance essayed, and cells remained in the flagellated-palmeloids green form whatever the culture conditions. High dilution rates produced small cells of 22 μm diameter, with a high nitrogen content of up to 10.0% d.wt. The average irradiance within the reactor was the main factor determining the behaviour of the cultures, although the external irradiance impinging on the reactor surface also influenced the results, indicating the existence of photoinhibition. The influence of both external and average irradiance on the growth of H. pluvialis was modelized. The accuracy of the model obtained was verified on a 0.22 m³ outdoor tubular photobioreactor operated in both discontinuous and continuous mode, obtaining a maximum biomass productivity of 0.68 g L⁻¹day⁻¹. The model reproduced the experimental data of biomass concentration and productivity, cell size and nitrate consumption, providing to be a powerful tool for optimizing the design and operation of outdoor photobioreactors for the production of green cells of H. pluvialis.     

Ethanol production from cheese whey permeate by Kluyveromyces marxianus UFV-3: A flux analysis of oxido-reductive metabolism as a function of lactose concentration and oxygen levels

In order to investigate the effect of lactose concentration and oxygen level on the growth and metabolism of Kluyveromyces marxianus UFV-3 in cheese whey permeate, batch cultures were conducted under aerobic, hypoxic, and anoxic conditions, with lactose at initial concentration ranging from 1 to 240 g L⁻¹. The increase in lactose concentration increased ethanol yield and ethanol volumetric productivity, and has reduced cell yield. When lactose concentration was equal or above 50 g L⁻¹ and the oxygen levels were low, the ethanol yield was close to its theoretical value. Maximum ethanol concentrations attained in this study were 76 and 80 g L⁻¹ in hipoxia and anoxia, respectively. The lactose consumption rate in anoxia was greater than in aerobiosis and hipoxia. However, under anoxia, the lactose consumption rate of K. marxianus followed a saturation kinetics, which was not observed in hypoxia and aerobiosis. All oxygen levels investigated, showed a tendency for saturation of the ethanol production rate above 65 g L⁻¹ lactose. Ethanol production rate was also higher on anoxia.     

Continuous ethanol production and evaluation of yeast cell lysis and viability loss under very high gravity medium conditions

A combined bioreactor system, composed of a stirred tank and a three-stage tubular bioreactor in series and with a total working volume of 3260 ml, was established. Continuous ethanol production was carried out using Saccharomyces cerevisiae and a very high gravity (VHG) medium containing 280 g l⁻¹ glucose. An average ethanol concentration of 124.6 g l⁻¹ or 15.8% (v) was produced when the bioreactor system was operated at a dilution rate of 0.012 h⁻¹. The yield of ethanol to glucose consumed was calculated to be 0.484 or 94.7% of its theoretical value of 0.511 when ethanol entrapped in the exhaust gas was incorporated. Meanwhile, quasi-steady states and non-steady oscillations were observed for residual glucose, ethanol and biomass concentrations for all of these bioreactors during their operations. Models that can be used to predict yeast cell lysis and viability loss were developed.     

Comparison of cyclohexanone monooxygenase as an isolated enzyme and whole cell biocatalyst for the enantioselective oxidation of 1,3-dithiane

Both whole cells of recombinant Escherichia coli TOP10, overexpressing cyclohexanone monooxygenase (CHMO) and isolated cyclohexanone monooxygenase, were used to carry out the enantioselective oxidation of 1,3-dithiane (1) to (R)-1,3-dithiane-1-oxide (2). The two biocatalysts were evaluated under various experimental conditions (e.g., shaken flask or bioreactor; non-bound or resin-adsorbed substrate; different substrate concentrations) in terms of volumetric productivity and enantioselectivity. While productivity was similar in the two cases (up to 0.58 g L⁻¹ h⁻¹), the optical purity of the product was much higher with the isolated enzyme (up to 98% e.e.) than with the whole cell biocatalyst (up to 85% e.e.).     

Allelopathic effects of Ulva lactuca on selected species of harmful bloom-forming microalgae in laboratory cultures

Allelopathic effects of the green macroalgae Ulva lactuca on the growth of three species of red tide microalgae, Heterosigma akashiwo, Alexandrium tamarense, and Skeletonema costatum were tested in laboratory co-cultures precluding the nutrient and light limitation and the effect of high pH. The growth of all three species of microalgae was significantly (p < 0.01) inhibited by fresh U. lactuca. In nutrient replete semicontinuous co-cultures with U. lactuca, H. akashiwo was completely dead in 12 days, and the growth of A. tamarense and S. costatum was reduced by 48 and 46%, respectively by U. lactuca within 12 days. The U. lactuca culture filtrate exhibited a significant (p < 0.05) inhibitory effect on the microalgae in the first 1 or 2 days, but growth resumed in the following days, and S. costatum growth was slightly (p > 0.05) promoted from day 3. The results suggested that the allelopathic compounds are quickly degradable and a long-term inhibition might need the continuous addition of compounds originated from macroalgae. Dried U. lactuca also exhibited inhibitory effects on the microalgae, and the normalized mean growth rates of microalgae decreased with the biomass of dried U. lactuca. The dependent relationships were y = −2.1208x² + 1.0159x + 0.9752 for H. akashiwo, y = 0.7133x² − 3.5813x + 1.1665 for A. tamarense, and y = −0.2114x² − 1.063x + 1.0873 for S. costatum, respectively. The potential feasibility of utilization of dried U. lactuca against red tide microalgae was 2.0 g dry wt L⁻¹. The present study shows that U. lactuca exhibits negative allelopathic effects on harmful bloom-forming microalgae.     

Effect of oxygen supply on cell growth and saponin production in bioreactor cultures of Panax ginseng

The effects of oxygen supply within the range 20.8–50% (using pure oxygen and air), on cell cultures of Panax ginseng were investigated in a balloon-type bubble bioreactor (5 L capacity, containing 4 L Murashige and Skoog medium, supplemented with 7.0 mg L⁻¹ indolebutyric acid, 0.5 mg L⁻¹ kinetin and 30 g L⁻¹ sucrose). A 40% oxygen supply was found to be optimal for the production of both cell mass and saponin yielding values of 12.8 g (DW) L⁻¹, 4.5 mg (g DW)⁻¹ on day 25, respectively. Low (20.8%, 30%) and high (50%) oxygen concentration supplies were unfavorable to cell growth and saponin accumulation. The results indicate that oxygen supplementation to bioreactor-based ginseng cultures was beneficial for biomass accumulation and saponin production.     

Effects of feed sugar concentration on continuous ethanol fermentation of cheese whey powder solution (CWP)

Cheese whey powder (CWP) solution with different CWP or sugar concentrations was fermented to ethanol in a continuous fermenter using pure culture of Kluyveromyces marxianus (DSMZ 7239). Sugar concentration of the feed CWP solution varied between 55 and 200 g l⁻¹ while the hydraulic residence time (HRT) was kept constant at 54 h. Ethanol formation, sugar utilization and biomass formation were investigated as functions of the feed sugar concentration. Percent sugar utilization and biomass concentrations decreased and the effluent sugar concentration increased with increasing feed sugar concentrations especially for the feed sugar contents above 100 g l⁻¹. Ethanol concentration and productivity (DP) increased with increasing feed sugar up to 100 g l⁻¹ and then decreased with further increases in the feed sugar content. The highest ethanol concentration (3.7%, v v⁻¹) and productivity (0.54 gE l⁻¹ h⁻¹) were obtained with the feed sugar content of 100 g l⁻¹ or 125 g l⁻¹. The ethanol yield coefficient (Y_P/S) was also maximum (0.49 gE gS⁻¹) when the feed sugar was between 100 and 125 g l⁻¹. The growth yield coefficient (Y_X/S) decreased steadily from 0.123 to 0.063 gX gS⁻¹ when the feed sugar increased from 55 to 200 g l⁻¹ due to adverse effects of high sugar contents on yeast growth. The optimal feed sugar concentration maximizing the ethanol productivity and sugar utilization was between 100 and 125 g l⁻¹ under the specified experimental conditions.     

Electrochemical quartz crystal impedance study on the overoxidation of polypyrrole-carbon nanotubes composite film for amperometric detection of dopamine

The electrochemical quartz crystal impedance (EQCI) method was used to study the overoxidation of polypyrrole (PPy)–multiwalled carbon nanotubes (MWCNT) nanocomposite film in neutral and alkaline solutions. The values of molar mass per electron transferred (M/n) obtained during the overoxidation of PPy in 0.10 mol L⁻¹ Na₂SO₄ and 0.20 mol L⁻¹ NaOH aqueous solutions were estimated to be ca. 17 and 22 g mol⁻¹, respectively, suggesting the nucleophilic attack of solution OH⁻ to the pyrrole units during the overoxidation, and the possible partial formation of carboxylic groups after the overoxidation in the NaOH solution. Also, the overoxidized PPy–MWCNT composite film prepared in the NaOH solution showed a notably larger affinity to dopamine (DA) dissolved in a neutral phosphate buffer than that prepared in the Na₂SO₄ solution. The modification of the overoxidized nanocomposite film improved substantially the sensitivity for DA assay in a neutral phosphate buffer, as compared with the modification of overoxidized PPy or MWCNT alone. At a −6 kHz (201-nm thickness) nanocomposite film prepared in a polymerization bath containing 1.0 mg mL⁻¹ MWCNT and overoxidized in 0.20 mol L⁻¹ aqueous NaOH, the peak current response from differential pulse voltammetric assay of DA was linear with DA concentration from 4.0 × 10⁻⁸ to 1.4 × 10⁻⁶ mol L⁻¹, with a lower limit of detection of 1.7 nmol L⁻¹, good anti-interferent ability, as well as good stability and reproducibility.     

Effect of feeding tree leaves as supplements on the nutrient digestion and rumen fermentation pattern in sheep grazing on semi-arid range of India – I

A study was carried out to determine the effect of feeding different tree leaves as supplements on nutrient digestion, rumen fermentation and blood parameters of sheep grazing on a semi-arid rangeland. Thirty adult Malpura rams of uniform body weight (39.0 ± 0.75) were divided into five groups of six each. They were grazed as a single flock from 08.00 to 17.00 h on a semi-arid rangeland. After the end of the grazing period, the first group (G1), which was not provided with any supplementation, served as the control. The second group (G2) was supplemented with 200 g of a concentrate mixture per head per day, whereas the third, fourth and fifth groups (G3–G5) were provided with approximately 200 g DM d⁻¹ of freshly cut foliage from Prosopis cineraria, Acacia nilotica and Albezia lebbek. The foliage from P. cineraria contained 133.4 g kg⁻¹ DM condensed tannin (CT) with protein precipitating capacity (PPC) of 66 g kg⁻¹ DM, whereas A. nilotica contained 18.9 g kg⁻¹ DM hydrolysable tannin (HT) with PPC of 11.5 g kg⁻¹ DM. However, A. lebbek did not contain any tannin. The protein contents were 119, 139 and 194 g kg⁻¹ DM, respectively. The DMI (g d⁻¹) was 688, 916, 1024, 1003, 999 in G1, G2, G3, G4 and G5, respectively. Digestible crude protein (DCP) and metabolizable energy (ME) intakes in supplemented groups G2–G5 were higher (P < 0.05) than in the control (G1). Supplementation improved the DM digestibility in all groups, whereas CP digestibility was lower (P < 0.05) in G3 compared to G2, G4 and G5. Rumen fermentation study conducted 6 h after supplementation revealed that total N, ammonia N, and total VFA levels were lower (P < 0.05) in G3 compared to the other supplemented groups. Although the haemoglobin (Hb) levels were similar among groups, blood urea N (BUN) was lowest in G3 compared to the other groups. The initial body weights were similar among groups (mean 39 kg). After 60 days of experimental feeding, all groups maintained their body weight, except the control group (G1), which lost body weight. It was observed, that supplementation with tree leaves containing CT like P. cineraria helps in better rumen fermentation pattern by preventing excessive loss of nitrogen. It was concluded that maximum nutritional benefits of tree leaves could be harvested, if used as supplement rather than as a sole feed.     

Biomass production and carbon dioxide fixation by Aphanothece microscopica Nägeli in a bubble column photobioreactor

The objective of the present study was to evaluate the growth kinetics of Aphanothece microscopica Nägeli under different conditions of temperature, light intensity and CO₂ concentration. The growth kinetics of the microorganism and carbon biofixation were evaluated using a central composite design, considering five different temperature levels (21.5, 25, 30, 35 and 38.5 °C), light intensities (0.96, 3, 6, 9 and 11 klux) and carbon dioxide concentrations (3, 15, 25, 50 and 62%). The results obtained showed the effects of temperature, light intensity and CO₂ concentration (p < 0.05) on the photosynthetic metabolism of the microorganism. Response surface methodology was adequate for process optimisation, providing a carbon fixation rate to the order of 109.2 mg L⁻¹ h⁻¹ under conditions of 11 klux, 35 °C and 15% carbon dioxide, representing an increase of 58.1% as compared to the conditions tested initially.     

The response of an emergent sedge Bolboschoenus medianus to salinity and nutrients

The potential for nutrient load (30, 100 and 350 g N m⁻² per year) to alter plant performance under saline conditions (control, 4.5, 9 and 13 dS m⁻¹) was examined in the sedge Bolboschoenus medianus. Relative growth rates (RGR) across nutrient loadings ranged from 30.2 to 41.8 mg g⁻¹ per day in controls and were reduced to 20.9–28.5 mg g⁻¹ per day by salinities of 13 dS m⁻¹. Whilst higher nutrient loads generally increased RGR, the response was smaller at higher salinities. Responses to salinity and nutrient load were specific. Nutrient load increased the RGR via increases in the leaf area ratio (LAR). The LAR ranged from 1.9 to 2.1 m² kg⁻¹ across salinity treatments at 30 g N m⁻² per year, and increased to 2.5–2.8 m² kg⁻¹ at 350 g N m⁻² per year. Salinity reduced the RGR via a reduction in the net assimilation rate (NAR). The NAR in control plants ranged from 14.7 to 16 g m⁻² per day across nutrient loadings and decreased to 11–12 g m⁻² per day at 13 dS m⁻¹. Carbon isotope discrimination of leaves decreased by 2–3‰ in response to 13 dS m⁻¹ at the lower nutrient loadings. A prominent response of B. medianus to salinity was a change in biomass allocation from culms to tubers. In contrast, the response to nutrient load was characterised by a shift in biomass allocation from roots to leaves.     

Determination of kinetic constants of hybrid textile wastewater treatment system

The present study is related to treatment of textile wastewater in microaerophilic–aerobic hybrid reactor. The study showed the effectiveness of biological treatment of wastewater involving appropriate microorganism and suitable reactors. COD and color were reduced to 82–94%, and 99% respectively for textile wastewater. The reactor was operated at highest loading of 16.4 g COD g l⁻¹ d⁻¹ and obtained 80% COD and 72% color removal. Biokinetic models were applied to data obtained from experimental studies in continuously operated hybrid reactor. Treatment efficiencies of the reactor were investigated at different hydraulic retention times (2.3–9.1 d) and organic loading rates (2.6–16.4 g COD l⁻¹ d⁻¹). Second-order and a Stover–Kincannon models were best fitted to the hybrid column reactor. The second-order substrate removal rate constant (k_2(S)) was found as 41.44 d⁻¹ for hybrid reactor. Applying the modified Stover–Kincannon model to the hybrid reactor, the maximum removal rate constant (U_max) and saturation value constant (K_B) were found to be 212 g l⁻¹ d⁻¹ and 22.89 g l⁻¹ d⁻¹, respectively.