Showing papers in "Bioprocess Engineering in 1987"

Viscous media in tower bioreactors: Hydrodynamic characteristics and mass transfer properties

Abstract: Studies in tower reactors with viscous liquids on flow regime, effective shear rate, liquid mixing, gas holdup and gas/ liquid mass transfer (k La) are reviewed. Additional new data are reported for solutions of glycerol, CMC, PAA, and xanthan in bubble columns with diameters of 0.06, 0.14 and 0.30 m diameter. The wide variation of the flow behaviour index (1 to 0.18) allows to evaluate the effective shear rate due to the gas flow. New dimensionless correlations are developed based on the own and literature data, applied to predict k La in fermentation broths, and compared to other reactor types.

In-situ recovery of butanol during fermentation

Abstract: End product inhibition can be reduced by the in situ removal of inhibitory fermentation products as they form. Extractive fermentation, in which an immiscible organic solvent is added to the fermentor in order to extract inhibitory products, was applied to the acetone-butanol fermentation. Six solvents or solvent mixtures were tested in batch extractive fermentations: kerosene, 30 wt% tetradecanol in kerosene, 50 wt% dodecanol in kerosene, oleyl alcohol, 50 wt% oleyl alcohol in a decane fraction and 50 wt% oleyl alcohol in benzyl benzoate. The best results were obtained with oleyl alcohol or a mixture of oleyl alcohol and benzyl benzoate. In normal batch fermentation of Clostridium acetobutylicum, glucose consumption is limited to about 80 kg/m3 due to the accumulation of butanol in the broth. In extractive fermentation using oleyl alcohol or a mixture of oleyl alcohol and benzyl benzoate, over 100 kg/m3 of glucose can be fermented. Removal of butanol from the broth as it formed also increased the rate of butanol production. Maximum volumetric butanol productivity was increased by as much as 60% in extractive fermentation compared to batch fermentation. Butanol productivities obtained in extractive fermentation compare favorably with other in situ product removal fermentations.

Propionic acid fermentation: improvement of performances by coupling continuous fermentation and ultrafiltration

Abstract: The present paper presents a study of propionic acid production from whey by using Propionibacterium acidipropionici in batch and continuous fermentation with cell recycle. The experimental investigation is carried through with a biomass concentration (DW) of 112kg/m3. The highest propionic acid productivity is 2.14 kg/(m3 h). Biomass concentration is 9 times as high, propionic acid productivity 6 times as high as compared to batch results.

Axial dispersion in plate-pulsed columns

Abstract: The residence time distribution (RTD) of the phase under continuous flow and dispersed flow was measured in a plate-pulsed column under countercurrent liquid-liquid flow, and modelled using (i) the axial dispersion model and (ii) the noninteger ideal stage cascade model. The axial mixing in the continuous phase was found to be significantly higher than in the dispersed phase. The model parameters were related to the operating conditions and system variables.

Kinetics of inhibition in propionic acid fermentation

Abstract: The inhibitory effect of propionic acid P and biomass concentration X is studied in batch and continuous fermentations with cell recycle.

Mixing performance of air-lift fermenters against working volume and draft tube dimensions

Abstract: Mixing characteristics of a laboratory scale internal loop air-lift fermenter has been investigated. The effects of different draft tube dimensions and positions as well as varying levels of liquid height over the draft tube, on mixing time were determined. The results indicate the existance of an optimum liquid height and thus liquid volume with respect to mixing performance especially for the taller draft tubes.

Fermentation coupled with microfiltration: kinetics of ethanol fermentation with cell recycle

Abstract: Cell recycle by microfiltration was used in yeast alcoholic fermentation in continuous operation. Toxins were proved to be washed by increasing dilution rate. — Specific ethanol production rate followed an exponential inhibition equation, which is function of both biomass concentration and dilution rate. — Productivity is shown to be 40 times greater than in conventional continuous operation.

Fundamental aspects of waste sewage sludge treatment: microbial solids biodegradation in an aerobic thermophilic semi-continuous system

Abstract: The solubilization and biodegradation of whole microbial cells by an aerobic thermophilic microbial population was investigated over a 72 h period. Various parameters were followed including total suspended solids reduction, changes in the dissolved organic carbon, protein and carbohydrate concentrations, and carboxylic acid production and utilisation. From the rates of removal of the various fractions a simple model for the biodegradation processes is proposed and verified with respect to acetic acid production and utilization, and total suspended solids removal. The process is initiated by enzymic degradation of the substrate microbe cell walls followed by growth on the released soluble substrates at low dissolved oxygen concentration with concommitant carboxylic acid production. Subsequent utilization of the unbranched, lower molecular weight carboxylic acids allows additional energy supply following exhaustion of the easily utilisable soluble substrate from microbial cell hydrolysis.

A database system for fermentation processes

Abstract: Data base management is needed in the whole industries, particularly in the fermentation industry, whose jobs are tedious yet require carefulness. The most important problem in the database system is not how to collect many informations, but how to handle the meaningful ones.

Development of anaerobic filters for treatment of high strength agro-industrial wastewaters

Abstract: The suitability and advantages of anaerobic filters for the treatment of various agro-industrial wastewaters are discussed. Recent developments in reactor design and typical operating parameters and performance data are given for reactors operated in the up- and downflow mode. The distribution of the most important process parameters throughout the reactor height is discussed and methods for process optimization are presented.

A biological system for studies on mixing in bioreactors

Abstract: A method for studying bioreactor inhomogeneity is suggested. Oxygen depletion in an E. coli cultivation leads to mixed acid fermentation with hydrogen gas production. Using a palladium metal-oxide semiconductor (Pd-MOS) hydrogen sensor on line in the effluent gas, it is shown that in a batch culture of 1 m3 hydrogen gas was evolved even before the dissolved oxygen tension (DOT) as measured by the probe reached zero. This suggests an appreciable degree of inhomogeneity with respect to DOT. Using measurements performed off line, it was observed that the lag time for hydrogen to appear became greater if the cells had been subjected to oxygen depletion. Lack of oxygen also resulted in a lowered hydrogen evolution capacity of the cells.

Biopolymer particulate turnover in biological waste treatment systems: a review

Abstract: Microorganisms — the major component in most biological waste treatment processes and a number of industrial fermentations — are not able to directly assimilate biopolymeric particulate material. Such organic particulates must first be solubilized into soluble polymers or monomers before they can diffuse through the capsular slime layer surrounding most bacteria, then transported across the cell membrane, to be used as either a carbon, energy or other essential nutrient source. Throughout these events, new cells are synthesized, which are themselves biopolymer particulates. The turnover of biopolymer particulates in biological treatment systems has not been examined with respect to its impact on system performance and culture physiology. The aim of this paper is to review the observations of particulate turnover in various biological treatment systems and to identify those fundamental mechanisms which govern microbial conversion of biopolymer particulates.

Separation of proteins by ion-exchange chromatography using gradient elution

Abstract: Chromatographic separation of proteins by the gradient elution method using DEAE Toyopearl 650® was carried through. The concentration gradient was effected by changing the ionic strength of NaCl in the carrier buffer solution. Bovine serum albumin and hemoglobin were used as model proteins for separation. The experimental chromatogram was compared with theoretical results of Yamamoto et al. [1, 2]. Adsorption equilibria of the proteins onto the carrier were measured and expressed by a function of the ionic strength. The retention volume and peak width of the resulting chromatogram can be calculated from the equilibrium data using the Yamamoto theory. The calculated results agreed well with the experimental data.

Growth of E. coli in a stirred tank and in an air lift tower reactor with an outer loop

Abstract: E. coli ATCC 11105 was cultivated in a 10-1 stirred tank reactor and in a 60-1 tower loop reactor in batch and continuous operation. By on-line measurements of O2 and CO2 concentrations in the outlet gas, pH, temperature, cell mass concentration X as well as dissolved O2 concentration along the tower in the broth, gas holdup, broth recirculation rate through the loop and by offline measurements of substrate concentration DOC and cell mass concentration along the tower, the maximum specific growth rate μ m , yield coefficients Y X/S. Y X/DOC and $$Y_{{\text{X/O}}_{\text{2}} }$$ were evaluated in stirred tank and tower loop in batch and continuous cultures with and without motionless mixers in the tower and at different broth circulation rates through the loop. To control the accuracy of the measurements the C balance was calculated and 95% of the C content was covered. The biological parameters determined depend on the mode of operation as well as on the reactor used. Furthermore, they depend on the recirculation rate of the broth and built-ins in the tower. The unstructured cell and reactor models are unable to explain these differences. Obviously, structured cell and reactor models are needed. The cell mass concentration can be determined on line by NADH fluorescence in balanced growth, if the model parameters are determined under the same operational conditions in the same reactor.

Development and efficiency of a new generation of bioreactors

Abstract: The development and investigation of high-efficiency bioreactors is one of the primary problems bioprocess engineers have to solve. With increasing efficiency of the bioreactor the downstream processes will be much simplified, energy and costs will be substantially reduced.

Modelling a solid-state fluidized bed fermenter for Ethanol production with S. cerevisiae

Abstract: A model is proposed to describe the performance of a new type of fermenter for ethanol production, the fluidized bed gas-solid fermenter, with respect to scaling-up effects. Based on the fact that in the fluid bed the substrate is not supplied continuously to each particle, two scale-up parameters are derived, circulation time τ and specific substrate supply Δm G,P , which are shown to influence reactor efficiency significantly. The validity of the model is checked by comparing the calculated yield coefficients for ethanol, cell mass and carbon dioxide to the results of fermentation experiments performed under aerobic conditions in a laboratory-scale reactor and a semi-technical fermenter.

Model aided design of repeated fed-batch penicillin fermentation

Abstract: Structured models of antibiotic fermentation that quantify maturation and aging of product forming biomass are fitted to experimental data. Conditions of superiority of repeated fed batch cultivation are characterized on the basis of a performance criterion that includes penicillin productivity and costs of operation. Emphasis is placed on the relevance of such research to the model aided design of optimal cyclic operation.

Survival and activity of Klebsiella pneumoniae at super-optimal temperatures

Abstract: The effect of temperature on a population of Klebsiella pneumoniae was examined together with the imposition of mild starvation conditions at temperatures of 35°, 41°, 49°, 55° and 60 °C Results for changes in biomass, protein and metabolic activity are presented in terms of gross population changes and show that these parameters decline with increasing temperature Increases in the amount of dissolved organic carbon, together with a decrease in the number of cells present with increasing temperature, suggest that death and lysis processes are occurring Regrowth in the bioreactor occurred after returning the temperature to 35 °C and starting a flow of carbon and other nutrients This was probably due to reinoculation from head space wall growth drainage rather than reversion of heat-stressed microbes The consequences of this for thermophilic sludge treatment processes are discussed The concept of endogenous metabolism is questioned with respect to it being a realistic description of the survival process

Simulation and optimization of fed-batch culture for ethanol production from molasses

Abstract: Two simulation methods for ethanol production from molasses by a flocculating yeast, Saccharomyces cerevisiae AM12, were investigated and molasses feeding was optimized. The first method was based on a deterministic model with fixed kinetic parameters and the second was based on regression analysis. The amount of ethanol produced in a fed-batch culture with multiple additions of molasses was simulated by both of these two methods. Simulated results of a fed-batch culture were compared with those of a simple batch culture by a model of regression analysis. The intermittent addition of molasses gave better production than a single addition at the beginning; more frequent addition may further improve production. The experimental results suggested the same. The effect of the amount of the added molasses on ethanol production was investigated by simulation. Repeated batch culture with and without intermittent addition of molasses in each batch was also done.

Penicillin acylase production by E. coli

Abstract: Enzyme production with E. coli ATCC 11105, in a complex medium using phenylacetic acid as inducer is carried out in a stirred-tank reactor of 10 dm3 and an airlift tower-loop reactor of 60 dm3 with outer loop at a temperature of 27 °C. The optimum inducer concentration was 0.8 kg/m3, which was kept constant by fed-batch operation. The optimum of the relative dissolved O2-concentration with regard to saturation is below 10% in a stirred-tank reactor and at 35% in a tower-loop reactor. It was kept constant by parameter-adaptive control of the aeration rate. In a stirred-tank enzyme productivity is slightly higher than in a tower-loop reactor, and much higher than in a bubble column reactor.

Process kinetic analysis of pleuromulin fermentation

Abstract: The industrial production of pleuromulin, an example for the production of secondary metabolites, has been carried out of the corporation Biochemie Kundl/Austria. The results of the experiments, especially the process kinetics are analyzed following the principles of the integrating strategy, which has been developed by the authors. Experiments on technical and laboratory scale were carefully designed and evaluated in order to allow an adequate insight in to this complex bioprocess. Typical plots are presented to illustrate the general macroscopic behaviour which serve as a reliable basis for process quantification. Mathematic modelling of this bioprocess will be presented in a following paper.

Intraparticle mass-transfer resistance and apparent time stability of immobilized yeast alcohol dehydrogenase

Abstract: The stability and, consequently, the lifetime of immobilized enzymes (IME) are important factors in practical applications of IME, especially so far as design and operation of the enzyme reactors are concerned. In this paper a model is presented which describes the effect of intraparticle diffusion on time stability behaviour of IME, and which has been verified experimentally by the two-substrate enzymic reaction. As a model reaction the ethanol oxidation catalysed by immobilized yeast alcohol dehydrogenase was chosen. The reaction was performed in the batch-recycle reactor at 303 K and pH-value 8.9, under the conditions of high ethanol concentration and low coenzyme (NAD+) concentration, so that NAD+ was the limiting substrate. The values of the apparent and intrinsic deactivation constant as well as the apparent relative lifetime of the enzyme were calculated.