Zinc uptake by Streptomyces rimosus biomass using a packed‐bed column

The ability of Streptomyces rimosus biomass to bind zinc ions in batch mode was shown recently. The aim of this study was to determine the zinc uptake capacity by Streptomyces rimosus biomass in continuous mode. Bacterial biomass was able to bind more Zn(II) after pretreatment with sodium hydroxide (1 mol dm⁻³) than without treatment. The maximum adsorption capacity and the adsorption capacity at the saturation point calculated by means of both the exchange zone model and the Thomas model were practically identical of about 2.9 mg_Zn(II) g⁻¹_biomass. This result was lower than the batch adsorption capacity of Streptomyces rimosus, indicating that the packed‐bed is not the most appropriate process to exploit the bacterial biomass adsorption capacity. The effect of zinc concentration in the range of 10 to 200 mg_Zn(II) dm⁻³ on the biosorption capacity of the packed‐bed was not significant. Biomass regeneration with 0.1 mol dm⁻³ HCl gave a 90% recovery of the adsorbed Zn(II). © 1999 Society of Chemical Industry     

Use of a genetic algorithm in the development of a synthetic growth medium for Arthrobacter simplex with high hydrocortisone Δ1-dehydrogenase activity

The production process for Arthrobacter simplex high specific hydrocortisone Δ¹-dehydrogenase activity and biomass yield (full experimental plan: 1·5 × 10¹⁴ experiments). The specific hydrocortisone Δ¹-dehydrogenase activity was improved by a vector of 4·5 to 1800 U g^?1. With the optimized medium composition in a stirred tank reactor for batch production of A. simplex, a specific hydrocortisone Δ¹-dehydrogenase activity of 2000–3000 U g^?1 dry biomass was achieved depending on harvest time (previously reported data: 18–37 U g^?1).     

Adsorption of cadmium and zinc from aqueous solution on natural and activated bentonite

The adsorption of cadmium and zinc ions on natural bentonite heat-treated at 110°C or at 200°C and on bentonite acid-treated with H₂SO₄ (concentrations: 0·5 mol dm^?3 and 2·5 mol dm^?3), from aqueous solution at 30°C has been studied. The adsorption isotherms corresponding to cadmium and zinc may be classified respectively as H and L types of the Giles classification which suggests the samples have respectively a high and a medium affinity for cadmium and zinc ions. The experimental data points have been fitted to the Langmuir equation in order to calcualte the adsorption capacities (X_m) and the apparent equilibrium constants (K_a) of the samples; X_m and K_a values range respectively for 4·11 mg g^?1 and 1·90 dm³ g^?1 for the sample acid-treated with 2·5 mol dm^?3 H₂SO₄ [(B)-A(2·5)] up to 16·50 mg g^?1 and 30·67 dm³ g^?1 for the natural sample heat-treated at 200°C [B-N-200], for the adsorption process of cadmium, and from 2·39 mg g^?1 and 0·07 dm³ g^?1, also for B-A(2·5), up to 4·54 mg g^?1 and 0·45 dm³ g^?1 [B-N-200], for the adsorption process of zinc. X_m and K_a values for the heat-treated natural samples were higher than those corresponding to the acid-treated ones. The removal efficiency (R) has also been calculated for every sample; R values ranging respectively from 65·9% and 8·2% [B-A(2·5)] up to 100% and 19·9% [B-N-200], for adsorption of cadmium and zinc.     

Effects of light wavelength and intensity on the production of ethanol by Saccharomyces cerevisiae in batch cultures

BACKGROUND: Photoreceptors have been identified in Saccharomyces cerevisae, however, the influence of light on the performance of ethanol fermentation of S. cerevisiae is not yet clear. The aims of this study are to elucidate the influence of light wavelength and intensity on the growth and ethanol production of S. cerevisiae and to describe a novel two‐stage LED light process to optimize ethanol fermentation. RESULTS: Experimental results indicated that maximum biomass concentration X_max of the batch under red LED light increased monotonically with light intensity, and the optimal specific product yield Y_p/x was 13.2 g g^?1 at 600 lux. Maximum ethanol concentration P_max of the batch under blue LED light increased monotonically with light intensity, and the optimal Y_p/x was 18.4 g g^?1 at 900 lux. A novel two‐stage LED light process achieved maximum P_max, of 98.7 g dm^?3 resulting in 36% improvement compared with that of the batch in the dark. CONCLUSION: The light wavelength and its intensity significantly affected cell growth and ethanol formation of S. cerevisiae. Red LED light (630 nm) stimulated cell growth but slightly inhibited ethanol formation. In contrast, blue LED light (470 nm) significantly inhibited cell growth but stimulated ethanol formation. A novel two‐stage LED light process has been successfully demonstrated to optimize ethanol fermentation of S. cerevisiae. Copyright © 2009 Society of Chemical Industry     

Partial nitrification of sludge reject water using suspended and granular biomass

BACKGROUND: Partial nitrification–Anammox is a combined promising advanced biological process for the removal of nitrogen from wastewater, which allows important savings in energy consumption, sludge production, and organic carbon. Granular biomass appears to be an interesting alternative to conventional activated sludge, mainly because of its better settling properties. This study deals with the experimental results of a comparison between a conventional and a granular sequencing batch reactor (SBR) for the partial nitrification of reject water. RESULTS: After some days of operation, 30 days in the conventional SBR (system A) and 100 days in the granular SBR (system B), partial nitrification was achieved. Granular sludge showed much better settling properties than suspended biomass, with values of sludge volumetric index (SVI₁₀) of 130 mL g^?1 in system A and 38 mL g^?1 in system B. Consequently, the solids concentration within the granular reactor was three times higher than for the conventional system while the concentration of solids in the effluent was 10 times higher in the conventional SBR. Morphology, microstructure and microbial populations in both systems were also studied. CONCLUSION: A partial nitrification process was successfully achieved in both systems, obtaining an effluent with a NO₂^?‐N/NH₄⁺‐N ratio near 1, suitable for a following Anammox process. Granular biomass, mostly formed by round particles, showed better settling properties, leading to better sludge–effluent separation as well as higher biomass retention in the reactor. The granulation process does not affect bacterial populations, since they were the same in both systems. Copyright © 2011 Society of Chemical Industry     

Intermediate accumulation and efficiency of anaerobic digestion treatment of surfactant (alcohol sulfate)‐rich wastewater at increasing surfactant/biomass ratios

Textile (eg cotton) finishing industry wastewater is characterised by high concentrations of surfactants (up to 2 g dm^?3) and of readily biodegradable biopolymers (COD 5–15 g dm^?3). The anionic surfactant decyl sulfate (DS) was chosen as model surfactant and soluble starch (size) as model compound for the readily biodegradable fraction of the wastewater. Twenty‐two batch experiments with increasing DS/biomass ratio (and starch/biomass ratio) were started simultaneously. Biomass concentrations ranged from 50 to 15 000 mg dm^?3. Minor inhibition effects were found for the surfactant degradation itself at all DS/biomass ratios (maximum biodegradation rate 7.7 mg_DS g_biomass^?1 h^?1). The starch hydrolysis started without a lag‐phase at DS/biomass ratios of up to 0.15 g_DS g_biomass^?1. The lag‐phase was prolonged to about 100 h at a very high DS/biomass ratio (3 g_DS g_biomass^?1). The relative importance of the accumulated intermediates was dependent on the DS/biomass ratio. Above 0.3 g_DS g_biomass^?1 10% of the substrate organic carbon accumulated as ethanol, but no ethanol accumulation was observed at low DS/biomass ratios. Moderate DS/biomass ratios caused a considerable delay of the methanogenesis; high DS/biomass ratios prevented the methanogenesis almost completely. © 2002 Society of Chemical Industry     

Development of a mathematical model for Bacillus circulans growth and alkaline protease production kinetics

BACKGROUND: An unstructured mathematical model was developed to understand information on the relationship between Bacillus circulans growth and metabolism‐related protease production (using logistic and Luedeking–Piret equations respectively) in a batch reactor with respect to glucose consumption and fermentation time. The objective was to develop an indispensable tool for the optimisation, control, design and analysis of alkaline protease production. RESULTS: Biomass growth and enzyme production titres changed with a change in substrate concentration. Modelling analysis of biomass and enzyme production titres at different substrate concentrations revealed significant accuracy in terms of statistical consistency and robustness with respect to fermentation kinetic profiles. CONCLUSION: With the B. circulans strain used, an economic protease yield (2837 × 10³ U g^?1) with respect to biomass and glucose ratio was achieved at low substrate concentration (10 g L^?1). The developed model could be effectively utilised for designing, controlling and up‐scaling the protease production process in high‐density fermentation in selected bioreactors with statistical consistency. Copyright © 2008 Society of Chemical Industry     

Batch and continuous decolorisation of bleached kraft effluents by a white-rot fungus

The white-rot fungus Coriolus versicolor, used in the form of mycelial pellets, provided an effective means to decolorise lignin-containing kraft E₁-stage effluent from wood treatment processes. The mycelial pellets adsorbed the chromophores of the liquor and oxidised them in the presence of glucose. For an original liquor containing 7000 colour units (CU), the mean colour removal in batch experiments was estimated to be 300 CU g^?1 mycelium h^?1. The adsorption process and the oxidation process (following glucose addition) generally operated best at between pH 4 and 5, and at temperatures of 25 to 30°C, with a ratio of glucose to mycelium of 0.36, for a 24 h experiment. Magnesium ions accelerated the oxidation process. Decolorisation was then tested in a continuous reactor. The rate of loss of activity of the pellets was 1% per day and no mechanical damage to the pellets was observed in the reactor. With a liquor of 5600 CU a 50% decolorisation was attained in 15 to 30 h using 4.64 g dm^?3 mycelium. This represents a rate of chromophore consumption of 30 CU g^?1 mycelium h^?1.     

Effects of experimental variables on phosphate adsorption on bentonite

The adsorption process of phosphate ions on a bentonite from Almería (East-Andalucía, Spain) was studied at 30°C over a range of experimental conditions such as saline (0.1 M KCl) or non-saline medium, natural or calcium homoionic bentonite and different pH values. In order to calculate the adsorption capacities (X_m) of the samples, the experimental data points were fitted to the Langmuir equation. X_m values ranged from 0.42 μg P g^?1 for the natural sample in non-saline medium to 0.74 μg P g^?1 for the same sample in saline medium, the X_m value corresponding to the calcium homoionic bentonite sample being intermediate. At different pH conditions, X_m increased from 0.28 μg P g^?1 at a pH of 1.3 to 1.53 μg P g^?1 at a pH of 4.4, and then decreased to 0.42 μg P g^?1 at a pH of 8.7.     

Biosorption of Zn(II) by orange waste in batch and packed‐bed systems

BACKGROUND: This research provides new insights into the biosorption of zinc on a waste product from the orange juice industry. Optimal operating conditions maximizing percentage zinc removal were determined in batch and fixed‐bed systems. Biomass was characterized by FTIR spectroscopy and by major cation content in order to better understand the biosorpion mechanism. Zn‐loaded orange waste was proposed to be used as an alternative fuel in cement kilns. RESULTS: Sorption capacity was strongly affected by biosorbent dose and solution pH, and was not strongly sensitive to particle size under the experimental conditions studied. Equilibrium data were successfully described by a Langmuir model and sorption kinetic data were adequately modelled with the pseudo‐second‐order and Elovich rate equation. The biomass was found to possess high sorption capacity (q_max = 0.664 mmol g^?1) and biosorption equilibrium was established in less than 3 h. Experimental breakthrough curves were adequately fitted to the Thomas model and the dose–response model, obtaining sorption capacities in continuous assays higher than those found in batch mode. Characterization of the biomass suggested the possible contribution of carboxyl and hydroxyl groups of biomass in Zn²⁺ biosorption and it also highlighted the important role of light metal ions in a possible ion‐exchange mechanism. CONCLUSIONS: Orange waste could be used as an effective and low‐cost alternative biosorbent material for zinc removal from aqueous solution. Copyright © 2010 Society of Chemical Industry     

Mathematical modelling of the alcoholic fermentation of glucose by Zymomonas mobilis mobilis

The kinetics of alcoholic fermentation of a strain of Zymomonas mobilis, isolated from sugarcane juice, has been studied with the objective of determining the constansts of a non-structured mathematical model that represents the fermentation process. Assays in batch and in continuous culture have been carried out with different initial concentrations of glucose. The final concentrations of glucose, ethanol and biomass were determined. The following kinetic parameters were obtained: μ_max, 0·5 h^?1; K_s, 4·64 g dm^?3; P_max, 106 g dm^?3; Y_x/s, 0·0265 g g^?1; m, 1·4 g g^?1 h^?1; α, 17·38 g g^?1; β, 0·69 g g^?1 h^?1.     

Investigation of zinc(II) adsorption on Cladophora crispata in a two‐staged reactor

In this study, the adsorption of zinc(II) ions on Cladophora crispata, a green alga, was studied with respect to initial pH, temperature, initial metal ion and biomass concentration in order to determine the optimum adsorption conditions. Optimum initial pH values for zinc(II) ions were found to be 5.0 at optimum temperature, 25 °C. The initial adsorption rates increased with increasing initial zinc(II) ion concentration up to 100 mgdm⁻³. The Freundlich and Langmuir adsorption isotherms were developed at various initial pH and temperature values. Then, the adsorption of zinc(II) ions to C crispata was investigated in a two‐staged mixed batch reactor. The residual metal ion concentrations (C_eq) at equilibrium at each stage for a given quantity of dried algae (X_o)/volume of solution containing heavy metal ion (V_o) ratio were calculated by using Freundlich and Langmuir isotherm constants. It was observed that the experimental biosorption equilibrium data for zinc(II) ions are in good agreement with those calculated using both Freundlich and Langmuir models. The adsorbed zinc(II) ion concentration increased with increasing X_o/V_o ratios while the adsorbed metal quantities per unit mass of dried algae decreased. © 2000 Society of Chemical Industry     

High efficiency bioethanol production from OPEFB using pilot pretreatment reactor

BACKGROUND: Current ethanol production processes using crops such as corn and sugar cane are well established. However, the utilization of cheaper biomasses such as lignocellulose could make bioethanol more competitive with fossil fuels while avoiding the ethical concerns associated with using potential food resources. RESULTS: Oil palm empty fruit bunches (OPEFB), a lignocellulosic biomass, was pretreated using NaOH to produce bioethanol. The pretreatment and enzymatic hydrolysis conditions were evaluated by response surface methodology (RSM). The optimal conditions were found to be 127.64 °C, 22.08 min, and 2.89 mol L^?1 for temperature, reaction time, and NaOH concentration, respectively. Regarding enzymatic digestibility, 50 FPU g^?1 cellulose of cellulase was selected as the test concentration, resulting in a total glucose conversion rate (TGCR) of 86.37% using the Changhae Ethanol Multi Explosion (CHEMEX) facility. Fermentation of pretreated OPEFB using Saccharomyces cerevisiae resulted in an ethanol concentration of 48.54 g L^?1 at 20% (w/v) pretreated biomass loading, along with simultaneous saccharification and fermentation (SSF) processes. Overall, 410.48 g of ethanol were produced from 3 kg of raw OPEFB in a single run, using the CHEMEX_50 L reactor. CONCLUSION: The results presented here constitute a significant contribution to the production of bioethanol from OPEFB. Copyright © 2011 Society of Chemical Industry     

Microfiltration of Streptomyces rimosus: Cell Harvesting Process Studies

ABSTRACT

Process studies were carried out to investigate the feasibility of using tangential crossflow microfiltration to harvest antibiotic-producing cells such as Streptomyces rimosus from a whole fermentation broth. The microorganism was grown in a repeated batch fermentation up to the point of secondary mycelium formation in order to simulate broth age and mycelial morphology present in the terramycin production process. Cell separation was carried out in a Millipore Pellicon system equipped with a Durapore 0.45 μm membrane cassette and operated in a batch concentration mode. Permeate fluxes for untreated fermentation broth were measured and compared with those for broth that was pretreated by acidification—a typical process step used to improve antibiotic recovery. Acidification from pH 7 to 4 prior to filtration changed the cell morphology and significantly reduced the inlet feed pressure required to pump the broth. In addition, pretreatment enabled higher crossflow rates and higher steady-state fluxes to be obtained at lower transmembrane pressures. Permeate fluxes for the pH-treated fermentation broth increased with operating temperature but were independent of further changes in pH     

In‐line mixing for production of citric acid by Candida lipolytica grown on n‐paraffins

This study reports on the effects of internal fermenter and external in‐line agitation and fed‐batch mode of operation on citric acid production from Candida lipolytica using n‐paraffin as the carbon source. An optimum range of fermenter agitation speeds in the range 800–1000 rpm corresponding to Reynolds numbers of 50433–62947 (based on initial batch conditions) seemed to give the best balance between substrate utilization for biomass growth and citric acid production. Proof of concept evidence is presented that indicates that an external in‐line agitator could be used in place of high speed internal agitation to increase citric acid production. However, more work is required to optimize the external agitator concept. Application of multiple fed‐batch feedings can be used to extend the batch fermentation and increase final citric acid concentrations and product yield. Experiments were conducted implementing a three‐cycle fed‐batch process which increased overall citric acid yields to 0.8–1.0 g citric acid g^?1 n‐paraffin, approximately 200% improvement from those found in the normal batch process. The three‐cycle fed‐batch mode of operation also increased the final citric acid concentration to 42 g dm^?3 from about 6 g dm^?3 for normal batch operation. Increased citric acid concentrations in three‐cycle fed‐batch mode was achieved at longer fermentation times. Copyright © 2004 Society of Chemical Industry     

Adsorptive removal of anionic and non‐ionic surfactants from aqueous phase using Posidonia oceanica (L.) marine biomass

BACKGROUND: In this study, the capability of low‐cost, renewable and abundant marine biomass Posidonia oceanica (L.) for adsorptive removal of anionic and non‐ionic surfactants from aqueous solutions have been carried out in batch mode. Several experimental key parameters were investigated including exposure time, pH, temperature and initial surfactant concentration. RESULTS: It was found that the highest surfactant adsorption capacities reached at 30 °C were determined as 2.77 mg g^?1 for anionic NaDBS and as 1.81 mg g^?1 for non‐ionic TX‐100, both at pH 2. The biosorption process was revealed as a thermo‐dependent phenomenon. Equilibrium data were well described by the Langmuir isotherm model, suggesting therefore a homogeneous sorption surface with active sites of similar affinities. The thermodynamic constants of the adsorption process (i.e. ΔG°, ΔH° and ΔS°) were respectively evaluated as ? 8.28 kJ mol^?1, 48.07 kJ mol^?1 and ? 42.38 J mol^?1 K^?1 for NaDBS and ? 9.67 kJ mol^?1, 95.13 kJ mol^?1 and ? 174.09 J mol^?1 K^?1 for TX‐100. CONCLUSION: Based on this research, valorization of highly available Posidonia oceanica biomass, as biological adsorbent to remove anionic and non‐ionic surfactants, seems to be a promising technique, since the sorption systems studied were found to be favourable, endothermic and spontaneous. Copyright © 2007 Society of Chemical Industry     

Performance evaluation of batch and unsteady state fed‐batch reactor operations for the production of a marine microbial surfactant

BACKGROUND: Biosurfactants are microbially derived surface‐active and amphipathic molecules produced by various microorganisms. These versatile biomolecules can find potential applications in food, cosmetics, petroleum recovery and biopharmaceutical industries. However, their commercial use is impeded by low yields and productivities in fermentation processes. Thus, an attempt was made to enhance product yield and process productivity by designing a fed‐batch mode reactor strategy. RESULTS: Biosurfactant (BS) production by a marine bacterium was performed in batch and fed‐batch modes of reactor operation in a 3.7 L fermenter. BS concentration of 4.61 ± 0.07 g L^?1 was achieved in batch mode after 22 h with minimum power input of 33.87 × 10³ W, resulting in maximum mixing efficiency. The volumetric oxygen flow rate (K_La) of the marine culture was about 0.08 s^?1. BS production was growth‐associated, as evident from fitting growth kinetics data into the Luedeking‐Piret model. An unsteady state fed batch (USFB) strategy was employed to enhance BS production. Glucose feeding was done at different flow rates ranging from 3.7 mL min^?1 (USFB‐I) to 10 mL min^?1 (USFB‐II). USFB‐I strategy resulted in a maximum biosurfactant yield of 6.2 g l^?1 with an increment of 35% of batch data. The kinetic parameters of USFB‐I were better than those from batch and USFB‐II. CONCLUSION: Comparative performance evaluation of batch and semi‐continuous reactor operations was accomplished. USFB‐I operation improved biosurfactant production by about 35% over batch mode. USFB‐I strategy was more kinetically favorable than batch and USFB‐II. © 2012 Society of Chemical Industry     

Cultivation of spirulina maxima in an annular photochemical reactor

An 8-L annular photochemical reactor has been designed and built for the cultivation of micro- or semi-microalgae at the laboratory scale. It may be operated in batch or continuous mode and is controlled for pH, temperature, gas mixture ratio (CO₂ and air), flow rate, light intensity and also illumination type (daylight or plant growth light) and mode (continuous or intermittent). It behaves as a perfect mixed reactor for all concentrations of algal cells. The reactor was used for the cultivation of the blue-green alga Spirulina maxima in a synthetic medium in both batch and continuous operations. At the dilution rate of 0.24 day^?1, the optimal productivity was 0.91 g/L-day for biomass or 0.55 g/L-day for protein. This is equivalent to 14.5 g/m²-day for biomass or 8.7 g/m²-day for protein. The optimal productivity as well as the chemical composition of the algal biomass were comparable to results obtained from pilot plant studies and reported in the current literature.     

Simulation of a membrane bioreactor for regeneration of degreasing systems

The dynamic behaviour of membrane bioreactors (MBRs) with negligible biomass growth due to the presence of toxic substances was modelled to simulate a pilot plant test in an industrial degreasing unit. Modelling was done by introducing a substrate biodegradation rate into a material balance equation of an MBR. This was followed by a discrimination procedure between the simulated and measured values, from which best‐fit specific substrate uptake rates (q_sp) were determined at different air supply rates. The results showed clear improvement of q_sp with increased air supply, indicating a possible increase in the active cell population in the reactor due to reduced toxicity. The highest specific substrate uptake rate (q_sp = 0.08 g_substrate g_biomass^?1 d^?1) determined was assumed equal to the maintenance coefficient (q_m) for the biodegradation of the substrate under the test conditions. The understanding of the dynamics provided a reference in subsequent regeneration system improvement. Copyright © 2006 Society of Chemical Industry     

Influence of Aerobic Pretreatment with Penicillium decumbens on the Anaerobic Digestion of Beet Molasses Alcoholic Fermentation Wastewater in Suspended and Immobilized Cell Bioreactors

A comparative study was carried out on the anaerobic digestion of untreated and previously-fermented (with Penicillium decumbens) beet molasses. Four continuous stirred tank reactors were used for the study, two with freely suspended biomass, and the other with biomass supported on saponite. The reactors operated satisfactorily between hydraulic retention times (HRT) of 53·3–10·6 days and 15·4–3·1 days for untreated and previously-fermented molasses respectively. The anaerobic digestion processes of untreated and pretreated molasses were found to follow first-order kinetics for biomass loading rates in the range of 0–0·55 and 0–0·75 g chemical oxygen demand (COD) g⁻¹ volatile suspended solids (VSS) day⁻¹ respectively. The experimental data [namely unitary conversion or efficiency (X), HRT, biomass concentration (M) and incoming substrate concentration (S₀)] conformed to an equation of the form: X/HRT = KM(1-X)–(KMS_R/S₀), from which the kinetic constant, K, was calculated. The kinetic constants were influenced by the pretreatment carried out and were 1·7 and 2·5 times higher for pretreated molasses than for untreated molasses in the reactors with suspended and immobilized biomass respectively. This was significant at a 95% confidence level. The specific rate of substrate uptake for cell maintenance (m) decreased by a factor of approximately 2 for the previously fermented molasses in relation to the observed values for the untreated molasses. This may be attributable to the fact that higher phenolic compound concentrations inhibit and interfere with the activity of anaerobic bacteria. © 1997 SCI.