Packed Column Bioreactor Research Articles

Production of dried Beauveria bassiana conidia in packed-column bioreactor using agro-industrial palm oil residues

Agro-industrial waste byproducts are commonly inexpensive organic nutritional sources for production of filamentous fungi, and selection of an optimal bioreactor is a key factor for attaining satisfactory biomass yield and quality. The insect-pathogenic fungus Beauveria bassiana (Hypocreales: Cordycipitaceae) has been extensively mass produced by solid-state fermentation using precooked cereal grains. Here, we propose low-cost palm oil residues as the main substrate using a cylindrical packed-column aerobic bioreactor prototype designed for conidial production of B. bassiana. Fermentation treatments using B. bassiana strain CG1229 assessed the impact of temperature, air flow, substrate moisture content, and ratio between palm fiber (PF) and palm kernel cake (PKC) on conidial yield and desiccation tolerance. Results showed significant enhanced productivity (2 ×1010 conidia g−1 dry matter) and reduced fermentation time (from 168 h to 120 h) by this method compared with the conventional tray bioreactor. Optimal substrate conditions were 60% initial moisture and 30% PF + 70% PKC content, fermentation at 26 °C with aeration rate ≥ 0.2 L min−1. Air drying conidia inside the column yielded > 95% germination. Maximum spore production was achieved in 120 h. Our findings demonstrate the feasibility of using a packed-column bioreactor for mass production of B. bassiana conidia using low-cost agricultural residues, which contributes to a sustainable production method of this biopesticide in Brazil.

Production of Citric Acid by Aspergillus niger Cultivated in Olive Mill Wastewater Using a Two-Stage Packed Column Bioreactor

For building a sustainable fermentation process, it is essential to reduce dependence on natural resources and lower the amount of pollution that is created. The reuse of agro-industrial wastewater after possible treatment leads to the achievement of these goals concurrently. This study investigates the production of citric acid and the cellulase enzyme by A. niger cultivated in olive mill wastewater (OMW) using a loofa sponge-packed column bioreactor. The process was conducted under batch conditions using a single-stage packed bioreactor and under continuous operation using two-stage packed-column bioreactors. Citric acid and cellulase enzyme production were enhanced when the culture was supplied with cellulose. Employing loofa sponge slices for cell entrapment/immobilization improved the efficiency of the process. The maximum citric acid concentration achieved was 16 g/L with a yield (YCit.A/BOD) of 38.5% and a productivity of 2.5 g/L/day. When the process parameters were translated into continuous operation employing two loofa sponge-packed column bioreactors, citric acid production was improved significantly to 25 g/L in a steady-state period of 5 days at a production rate of 3.6 g/L/day and an allover yield (YCit.A/BOD) of 57.5%. Cellulases and reducing sugars were continuously supplied to the second-stage bioreactor by the first-stage bioreactor, which in turn enhanced fungal growth and citric acid production.

Forced aeration promotes high production and productivity of infective conidia from Metarhizium robertsii in solid-state fermentation

Metarhizium genus is an important biological control agent. Most industrial conidia production processes are based on the use of plastic bags or containers containing ∼1 kg of substrate. Static bioreactors, such as packed columns, trays, and plastic bags, are used for different scale conidia production. However, the effect of aeration mechanism on conidia production and quality has not been evaluated. Therefore, the productivity and quality of conidia produced in three types of bioreactors were evaluated. M. robertsii strain Xoch 8.1 was used to determine the effect of temperature and airflow rate on conidia production and quality. The productivity of viable conidia in the packed column bioreactor was up to 1.8 and 1.5 times higher than that obtained with tray and bag bioreactors, respectively. Conidial infectivity was similar for the three types of bioreactors. Forced convection aeration in the packed columns resulted in higher levels of conidia production and productivity without affecting their quality. This study shows that forced aeration in tubular bioreactor allows the highest conidia production and productivity; additionally, the forced aeration allows the on-line monitoring of the production of CO2 during the fermentation process, as a tool to associate this measurement to conidiation patterns.

Solution pH and Jarosite Management during Ferrous Iron Biooxidation in a Novel Packed-Column Bioreactor

Jarosite formation is undesirable in bioleaching processes as it depletes the needed ferric reagent for the oxidation of most sulfide minerals. Although it creates kinetic barriers thereby retarding the leach rates of most minerals, jarosite serves as support for the attachment of bioleaching microbes, facilitating biooxidation rate. Microbial ferrous-oxidation by mesophilic microbe was studied in a recently reported novel packed-column bioreactor with a view to investigate the potential of using solution pH to manage jarosite accumulation in the bioreactor in addition to establishing a base case data for the bioreactor. Experiments were conducted in the bioreactor packed with glass balls (15mm diameter) at constant temperature of 38.6 °C, residence time of 18 hours, airflow rate of 20 mLs-1and pH values of 1.3, 1.5 and 1.7. The results showed that the amount of jarosite accumulation is proportional to the solution pH, and to the duration of operation of the bioreactor. Jarosite precipitation concentrations of 4.95, 5.89 and 7.08 gL-1were obtained after 10 days of continuous operation at solution pH values of 1.3, 1.5 and 1.7 respectively, while after 15 days the precipitations concentrations increased to 5.50, 7.90, 9.98 gL-1respectively. The results also showed that 33% and 52% precipitate reduction could be achieved by gradual decrease in the bioreactor solution pH to 1.5 and 1.3 after being continuously operated for 10 days at pH 1.7 respectively after an addition of 5 days. A maximum ferrous oxidation rate (), 6.85 mmol.L-1.h-1and the affinity kinetic constants (,), of 0.001 and 0.006 for Hansford and Monod models respectively. Although a directly relationship exist between jarosite formation and pH, the results of this study may be relevant in bioleach heaps or at least in column bioreactors to manage/control jarosite accumulation thereby improving the leach kinetics of mineral sulfides.

Investigation of ferrous-iron biooxidation kinetics by Leptospirillum ferriphilum in a novel packed-column bioreactor: Effects of temperature and jarosite accumulation

The kinetics of microbial ferrous-iron by Leptospirillum ferriphilum was studied at substrate loading rate of 3–90mmolL−1h−1 in a novel packed column bioreactor. The study was conducted with a view to providing an understanding of the reaction kinetics in a flow-through system which may be assumed to mimic bioheap solution flow, rather than the more typical batch reactors. The bioreactor was maintained at pH of 1.45±0.05 and constant air flow rate of 15mLs−1. The Boon and Hansford, and the Monod models accurately described the experimental data. The effect of temperature on the kinetic parameters was investigated at 25, 30 and 35°C. The maximum oxidation rate, rFe2+max=15.10mmolL−1h−1, was highest at 35°C. The activation energy, Ea=20.97kJmol−1, of ferrous-iron biooxidation in the novel bioreactor is indicative of a system that is limited by both biochemical and diffusion factors. The result also showed about 38.80% increase in the maximum microbial ferrous-iron oxidation,rFe2+max, due to accumulation of jarosite. However, the decreasing values of substrate affinity constant, KFe2+, and the apparent affinity constant, K′Fe2+ revealed that the microbial affinity for ferrous biooxidation increases with increase in jarosite formation. This study reveals that jarosite maybe beneficial to bioleach heaps if it is carefully managed.

Model-Based Analysis of a Phenol Bio-Oxidation Process by Adhered and Suspended Candida tropicalis

Phenol is an important commodity for the chemical industry, used for many processes and deemed to be a major pollutant due its xenobiotic nature and high toxicity. For the purpose of phenol bioremediation a biotechnological set up consisting of a continuous packed column bioreactor with Candida tropicalis adhered onto activated carbon beads has been previously described. In this work, we show how the integration of available experimental data of such a biotechnological set up into a mathematical model, can lead both to a better comprehension of the underlying physiological mechanisms operating in the cell culture, and to the identification of the system parameters optimum performance. The model so constructed describes the dynamics of phenol uptake and growth rates by the adhered and suspended biomass; the lethality rates; the adhered biomass removal into suspension or adherence onto carbon beads rates and the phenol and biomass (adhered and suspended) concentrations. It also serves to identify different physiological states for the adhered and the suspended biomass; its predictions being verified by comparing with experimental observations. Based on the model description, different optimization strategies are proposed, some of which have been experimentally tested, encompassing changes in bioreactor operation conditions, process development and strain development.

Leaching of a zinc ore and concentrate using the Geocoat™ technology

In this study, the Geocoat™ technology was used for the extraction of zinc from a mineral concentrate obtained from the Kooshk mine (Yazd, Iran) by a culture dominated by the mesophilic bacterium Acidithiobacillus ferrooxidans in a packed column bioreactor. A low grade sphalerite ore was used as support for the concentrate coating. During the 100 days of leaching pH, Fe 3+, Fe total, microbial population density and zinc extraction were measured. The final zinc extraction from concentrate and low grade support was 97% and 78%, respectively, and it was found that leaching from the support does not proceed significantly before leaching from the coating is completed.

Fermentation of cheese whey powder solution to ethanol in a packed‐column bioreactor: effects of feed sugar concentration

AbstractBACKGROUND: Cheese whey powder (CWP) is a concentrated source of lactose and other essential nutrients for ethanol fermentation. CWP solution containing different concentrations of total sugar was fermented to ethanol in an up‐flow packed‐column bioreactor (PCBR) at a constant hydraulic residence time (HRT) of 50 h. Total sugar concentration in the feed was varied between 50 and 200 g L−1 and a pure culture of Kluyveromyces marxianus was used for ethanol fermentation of lactose. Variations of ethanol and sugar concentrations with the height of the column and with the feed sugar concentration were determined.RESULTS: Ethanol concentration increased and total sugar decreased with the column height for all feed sugar contents. The highest effluent ethanol concentration (22.5 g L−1) and ethanol formation rate were obtained with feed sugar content of 100 g L−1. Percentage sugar utilization decreased with increasing feed sugar content above 100 g L−1 yielding lower ethanol contents in the effluent. The highest ethanol yield coefficient (0.52 gE g−1S) was obtained with a feed sugar content of 50 g L−1. Biomass concentration also decreased with column height, yielding low ethanol formation in the upper section of the column.CONCLUSION: The packed column bioreactor was found to be effective for ethanol fermentation from CWP solution. The optimum feed sugar content maximizing the effluent ethanol and the specific rate of ethanol formation was found to be 100 g L−1. High sugar content above 100 g L−1 resulted in low ethanol productivities due to high maintenance requirements. Copyright © 2008 Society of Chemical Industry

Ethanol production from cheese whey powder solution in a packed column bioreactor at different hydraulic residence times

Cheese whey powder (CWP) solution containing 50 g L −1 total sugar was fermented to ethanol in a continuously operated packed column bioreactor (PCBR) using olive pits as support particles for cell attachment. Pure culture of Kluyveromyces marxianus (DSMZ 7239) was used in the PCBR for ethanol formation from lactose content of CWP solution. Sugar utilization and ethanol formation were investigated as function of the hydraulic residence time (HRT) between 17.6 and 64.4 h. Sugar concentration decreased with increasing ethanol concentration along the height of the column. Percent sugar utilization increased while effluent sugar concentration was decreasing with HRT between 17.6 and 50 h. Similarly, effluent ethanol concentration increased while ethanol productivity was decreasing with increasing HRT up to 50 h. Further increases in HRT above 50 h resulted in decreases in effluent ethanol concentration. The ethanol yield coefficient also increased with increasing HRT and reached the highest level of 0.54 gE g −1S at an HRT of 50 h. Due to cell settling to the bottom of the column, high fermentation rates were obtained in the lower section of the system. Therefore, the system can be operated with a height of 36 cm from the inlet to obtain high ethanol contents in the effluent with an HRT of 18 h.

Scale up studies for the production of biosurfactant in packed column bioreactor

Biosurfactants capable of emulsifying pesticides have great potential to assist in microbial degradation of the pesticides. Solid State Fermentation (SSF) due to several advantages, is one of the efficient ways of producing these surfactants and seldom receives attention for commercial exploitation. In this study, a packed column bioreactor with wheat bran as the raw material and Bacillus subtilis has been used to produce a biosurfactant specific to disperse Fenthion, an organophosphrous pesticide. The emulsifier activity (EA) and surface tension from the packed column bioreactor were compared with flask fermentation experiments, which served as control. Airflow rate in the packed column bioreactor was varied from 10–20 l/min. Maximum EA and minimum surface tension occurred at airflow rate of 20 l/min. Peak EA in the control was 1.2 at 29 h while it was 1.9 in the bioreactor. The least surface tension of 24 dynes/cm was noticed at 54 h in the bioreactor, which was 33% better than the control at the same time period. The results indicate that the packed column bioreactor can become a more acceptable solid state fermentation system for commercial exploitation of Fenthion specific biosurfactant production.

Immobilization of Brevibacterium Cells for the production of l-glutamic acid

Studies were performed to elucidate the optimal conditions (gel concentration, bead size, initial biomass, storage period) for immobilization of growing cells of Brevibacterium sp. (DSM 20411) in alginate and agar gels and to evaluate the immobilized biocatalyst in batch mode, and continuous mode in a packedcolumn bioreactor, for l-glutamic acid production. The entrapped cells were also cultivated for fwenty five days in five repeated batches (each batch lasted for five days). Maximum l-glutamic acid production in batch and repeated-batch modes was 7.4 and 8.7 mglml, respectively, with alginate beads, and 11.8 and 13.3mg/ml, respectively, with agar beads. Under optimized conditions (flow rate, initial cell loading), l-glutamate productivity was maintained within a range 10–11 mg/ml for two weeks, in continuous mode, in a packed column bioreactor with agarimmobilized cells.

Interaction of transport resistances with biochemical reaction in packed-bed solid-state fermentors: Effect of temperature gradients

In solid-state fermentation, the interaction of transport phenomena with biochemical reactions has a considerable effect on the productivity of the bioreactor. Previous work on solid-state fermentation in tray fermentors in our laboratory indicated that heat transfer resistance results in steep temperature gradients within the solid substrate bed, which in turn adversely affect the biochemical reaction and enzyme activity. This problem of heat accumulation during the course of fermentation has been alleviated to a considerable extent using a packed-column bioreactor with forced aeration in the present work. Experimental studies were conducted in a packed-column bioreactor utilizing wheat bran as substrate and the fungus Aspergillus niger CFTRI 1105 for the production of the enzyme amyloglucosidase. The enzyme activities were estimated and temperatures were recorded at different bed heights, for different air flow rates during the course of fermentation. The results indicated that the temperature gradients caused by heat transfer resistances were reduced considerably with corresponding increases in enzyme activity.

Gas concentration and temperature gradients in a packed bed solid-state fermentor

In solid-state fermentation (SSF), interaction of heat and mass transfer with biochemical reaction (growth associated enzyme production) affects the bioreactor performance. This interaction was earlier observed to cause temperature and gaseous concentration gradients which reduced the effective bed height of the bioreactor. Since forced aeration is known to alleviate this problem, a packed column bioreactor with forced aeration was employed in the present study. Using wheat bran and Aspergillus niger CFTRI 1105, experiments were conducted for the production of the enzyme amyloglucosidase at various air flow rates. Temperatures and gas concentrations were recorded and enzyme activities estimated at different bed heights during the course of SSF. Gas concentration and temperature gradients decreased with increasing air flow rate. The packed column allowed the use of larger bed heights and yielded higher enzyme activities (6,260 Units/gDMB) than trays (345 Units/gDMB). Enzyme activity was affected more by temperature than concentration gradients, and increased with air flow rates.

Bioconversion of gallic acid into pyrogallol by immobilized Citrobacter freundii TB3

Abstract A laboratory isolate of Citrobacter freundii immobilized in κ-carrageenan was used for the bioconversion of gallic acid into pyrogallol. In batch fermentation, 20% (w/v) bead concentration produced maximum pyrogallol (5.53 g/ l ) from 10 g/ l of gallic acid. In repeated batch fermentation, the pyrogallol concentration increased until the third cycle (6.8 g/ l ) and remained steady thereafter. Continuous fermentation was performed using a packed column bioreactor. The maximum production of 7.3 g/ l (98.5% conversion) was obtained at the flow rate of 0.5 ml/min.