Degradation of quinoline by immobilized Comamonas acidovorans in a three-phase airlift reactor

Quinolie degradation by Comamonas acidovorans was studied in a continuously operated three-phase airlift reactor. Porous glass beads were applied as support matrix for cell imobilization by colonization. Under steady-state conditions (S approximately 0), cell attachment was poor at low dilution rates but imporved considerably with increasing dilution rate. Conversion of quinoline was investigated below and above the washout for suspended culture (D(crit) = mu(max) = 0.42 h(-1)). With immobilized cells the reactor could be operated at D > mu(max), and complete conversion of quinoline was achieved as long as the specific quinoline feed rate D*S(0)/X did not exceed the maximum specific degradation rate (r(S, max)). The biofilm thickness was about 100 mum, and its efficiency was about 54% compared to suspended organisms. If quinoline overloads were supplied to the reactor, quinoline, as overloads were supplied to the reactor, quinoline, as well as its pathway intermediates, appeared in the reactor and conversion was low. Hence, the immobilized microorganisms remained viable and active. They could survive quinoline overloads. If the quinoline feed rate was reduced agains, complete conversion was reestablished. (c) 1995 John Wiley & Sons, Inc.     

一株耐高盐热带假丝酵母菌降解苯酚的研究

从含酚废水处理池污泥中驯化分离得到一株能以苯酚为唯一碳源的菌株FD-1。经18SrDNA和ITS序列的BLAST比对及系统发育分析,鉴定FD-1为热带假丝酵母(Candida tropicalis)的近缘种。FD-1对苯酚的降解能力较强,能够完全降解浓度为1 000mg·L-1的苯酚溶液。初步确定了FD-1在降解苯酚溶液时的最适温度为30~35℃,pH为6.0~7.0,并且通过探讨加入无机盐、培养基原料以及改变接种量三个因素对苯酚降解的影响,其耐受盐的浓度可达5%,对实践中应用微生物降解含酚废水具有积极的意义。     

Formation of nitrifying biofilms on small suspended particles in airlift reactors

For a stable and reliable operation of a BAS-reactor a high, active biomass concentration is required with mainly biofilm-covered carriers. The effect of reactor conditions on the formation of nitrifying biofilms in BAS-reactors was investigated in this article. A start-up strategy to obtain predominantly biofilm-covered carriers, based on the balancing of detachment and a biomass production per carrier surface area, proved tp be very successful. The amount of biomass and the fraction of covered carrier were high and development of nitrification activity was fast, leading to a volumetric conversion of 5 kg(N) . m(-3) . d(-1) at a hydraulic retention time of 1h. A 1-week, continuous inoculation with suspended purely nitrifying microorganisms resulted in a swift start-up compared with batch addition of a small number of biofilms with some nitrification activity. The development of nitrifying biofilms was very similar to the formation of heterotrophic biofilms. In contrast to heterotrophic bio-films, the diameter of nitrifying biofilms increased during start-up. The detachment rate from nitrifying biofilms decreased with lower concentrations of bare carrier, in a fashion comparable with heterotrophic biofilms, but the nitrifying biofilms were much more robust and resistant. Standard diffusion theory combined with reaction kinetics are capable of predicting the activity and conversion of biofilms on small suspended particles. (c) 1995 John Wiley & Sons Inc.     

Two-phase culture for enhanced alkaloid synthesis and release in a new airlift reactor by Catharanthus roseus

A new airlift reactor was used to culture Catharanthus roseus cells, in which the draft tube was made up of polyurethane foam and acted as the immobilizing matrix. The reactor was connected in series to an adsorbent column with a neutral polymeric resin which absorbs these alkaloids. The synthesis of alkaloid was stimulated by adding the resin column and the total content of alkaloid secreted by cells reached 380 mg/L, which was 4.5 times of that in the control experiment. Meanwhile, most of the intracellular alkaloid produced by Catharanthus roseus was secreted into the medium.     

Economic comparison of enzymatic reactors and advanced oxidation processes applied to the degradation of phenol as a model compound

Abstract

Some micropollutants present in wastewaters are barely removed in sewage treatment plants. In many cases a post-treatment process based on separation and/or oxidation has to be applied. The aim of this study was the technical and economic comparison of enzymatic technologies with other advanced oxidation processes (AOPs) for the degradation of phenol. Batch and continuous enzymatic reactors, using free and immobilized manganese peroxidase (MnP, EC 1.11.1.13), were considered. Continuous degradation of phenol in an enzymatic membrane reactor was shown to be the fastest process and degradation in a continuous reactor with immobilized enzyme involved the lowest consumption of enzyme. However, the immobilization process increased the enzyme cost 100-fold. A continuous enzymatic membrane reactor gave high degradation efficiency and may be a viable technology for phenol removal when compared with other AOPs from both technical and economic points of view.     

Dynamics of biofilm detachment in biofilm airlift suspension reactors

The dynamic change in the overall detachment rate of spherical biofilms in a biofilm airlift suspension reactor was measured after a downshift of the substrate loading rate to zero while all other conditions remained constant. In contrast to the expectations, the overall detachment rate decreased rapidly to a nearly stable level. Correlations available from literature were not able to describe this phenomenon. Concepts were formulated which can describe the observations from this study. Research under dynamic conditions and careful monitoring of the biofilm surface area and biofilm morphology are necessary to elucidate and discriminate biofilm detachment mechanisms. (c) 1995 John Wiley & Sons, Inc.     

苯酚高效降解菌的筛选和降解特性的研究

从天津市煤气厂的活性污泥中筛选、分离得到一株高效苯酚降解菌。经BIOLOG细菌自动鉴定系统及16SrDNA鉴定,该菌株为粪产碱杆菌(Alcaligenesfaecalis)。苯酚降解实验证实,该菌能在76h内完全降解1600mg·L-1的苯酚,并且随着苯酚浓度的增加,底物抑制作用增强,细胞得率下降。     

Formation and growth of heterotrophic aerobic biofilms on small suspended particles in airlift reactors

In this article, the conditions for aerobic biofilm formation on suspended particles, the dynamics of biofilm formation, and the biomass production during the start-up of a Biofilm Airlift Suspension reactor (BAS reactor) have been studied. The dynamics of biofilm formation during start up in the biofilm airlift suspension reactor follows three consecutive stages: bare carrier, microcolonies or patchy biofilms on the carrier, and biofilms completely covering the carrier. The effect of hydraulic retention time and of substrate loading rate on the formation of biofilms were investigated. To obtain in a BAS reactor a high biomass concentration and predominantly continuous biofilms, which completely surround the carrier, the hydraulic retention time must be shorter than the inverse of the maximum growth rate of the suspended bacteria. At longer hydraulic retention times, a low amount of attached biomass can be present on the carrier material as patchy biofilms. During the start-up at short hydraulic retention times the bare carrier concentration decreases, the amount of biomass per biofilm particle remains constant, and biomass increase in the reactor is due to increasing numbers of biofilm particles. The substrate surface loading rate has effect only on the amount of biomass on the biofilm particle. A higher surface load leads to a thicker biofilm.A strong nonlinear increase of the concentration of attached biomass in time was observed. This can be explained by a decreased abrasion of the biofilm particles due to the decreasing concentration of bare carriers. The detachment rate per biofilm area during the start-up is independent of the substrate loading rate, but depends strongly upon the bare carrier concentration.The Pirt-maintenance concept is applicable to BAS reactors. Surplus biomass production is diminished at high biomass concentrations. The average maximal yield of biomass on substrate during the experiments presented in this article was 0.44 +/- 0.08 C-mol/C-mol, the maintenance value 0.019 +/- 0.012 C-mol/(C-mol h). The lowest actual biomass yield measured in this study was 0.15 C-mol/C-mol. (c) 1994 John Wiley & Sons, Inc.     

Kinetics of methanogenic degradation of phenol by activated-carbon-supported and granular biomass

A continuous-feed recycle bioreactor was used to study the kinetics of methanogenic degradation of phenol at 35 degrees C by bacteria supported on a bed of granular activated carbon (GAC). At dilution rates well above the growth rate of the culture, the cells not only populated the GAC, but also formed a layer of granular biomass. This layer was stabilized by the presence of the GAC, and accounted for over half of the phenol-degrading activity in the bioreactor. The specific phenol degradation rates for GAC-attached biomass, suspended biomass, and granular biomass were all in the range 0.15 to 0.22 mg phenol/mg volatile solids per day as measured under pseudo-steady-state conditions. (c) 1992 John Wiley & Sons, Inc.     

Oxygen transfer modeling and simulations for an industrial continuous airlift fermentor

This article deals with the modeling of the oxygen transfer in an industrial airlift fermentor used for lactic yeast production on whey substrates. The purpose of this study was to improve the understanding of the interactions among the various parameters that govern the oxygen transfer phenomena in this type of fermentor. The reliability of the proposed model is demonstrated. The results of the investigations have been put into practice on the industrial scale and have contributed to monitor better the fermentation process. The model was also used to develop new ways of industrial fermentor design.     

Isolation and Characterization of High-Strength Phenol-Degrading Novel Bacterium of the Pantoea Genus

A new indigenous soil bacterium Pantoea strain NII-153 utilizing phenol as a sole carbon source was isolated and characterized. Phylogenetic analysis suggested its classification to the Enterobacteriaceae family, with 95.0% gene sequence similarity to Pantoea ananatis ATCC 33244. Biodegradation rates of phenol by NII-153 were found to be more effective at 64 h with initial concentration of 600 mg L^{? 1} of phenol and this is the first report of such activity in Pantoea species. Strain NII-153 has showed high tolerance to phenol concentration (900 mg L^{? 1}). Therefore, strain NII-153 could be used for biotreatment of high-strength phenol-containing industrial effluents and for bioremediation of phenol-contaminated soils.     

Biotransformation kinetics of Pseudomonas putida for cometabolism of phenol and 4-chlorophenol in the presence of sodium glutamate

A kinetic model to describe the degradation of phenol and cometabolictransformation of 4-chlorophenol (4-cp) in the presence of sodium glutamate(SG) has been developed and validated experimentally. The integrated modelaccounts for cell growth, toxicity of 4-cp, cross-inhibitions among the threesubstrates, and the different roles of the specific growth substrate (phenol)and the conventional carbon source (SG) in the cometabolism of 4-cp. In thisternary substrate system, the overall phenol degradation and 4-cp transformation rates are greatly enhanced by the addition of SG since SG is able to attenuate the toxicity of 4-cp and therefore increase the cell growth rate. Model analysis indicates that the maximum specific degradation rate of phenol (0.819 mg (mg.h)^-1) is lowered by SG by up to 46% whereas the specific transformation rate of 4-cp is notdirectly affected by the presence of SG. The competitive inhibition coefficient of 4-cp to phenol degradation (K_i,cp) and that of phenol to 4-cp transformation (K_i,ph) were determined to be 6.49 mg l^-1 and 0.193 mg l^-1, respectively, indicatingthat phenol imposes much larger competitive inhibition to 4-cp transformation than the converse. The model developed can simultaneously predict phenol degradation and 4-cp transformation, and is useful for dealing with cometabolism involving multiple substrates.     

Selective recycle of viable animal cells by coupling of airlift reactor and cell settler

A new system for the perfusion culture of animal cells in suspension is described. It consists of an airlift loop reactor and a settling tank for cell retention. Insufficient nutrient and oxygen supply of the cells in the settling tank was prevented by cooling the cell suspension before entering the settler. As a result, the catabolic activity of the cells in the settler was reversibly reduced. Furthermore, the density gradient induced by cooling caused a liquid motion through the settler. Thus, it was not necessary to pump medium containing shear, sensitive cells. With this simple system, it was possible to prduce 2 to 5 g of antibodies in a 5.4-L reactor in continuous runs of 400 to 600 h. The productivity was increased by a factor of 17 and the cell density was 4 times higher in comparison with the corresponding batch system. The cell retention system was found to have the property of separating viable and nonviable cells. With the increasing perfusion rate, dead cells and debris were preferably washed out. For perfusion rates up to 1.3 d(-1), the retention efficiency of the settler was nearly 100% for viable cells; hence, this system may show advantages at the industrial scale.     

Characterization of a pilot plant airlift tower loop bioreactor: II. Evaluation of global mixing properties of the gas phase during yeast cultivation

Saccharomyces cerevisiae was cultivated in a 4-m(3) pilot plant airlift tower loop reactor with a draft tube in batch and continuous operations and for comparison in a laboratory airlift tower loop reactor of 0.08 m(3) volume. The reactors were characterized during and after the cultivation by measuring the distributions of the residence times of the gas phase with pseudostochastic tracer signals and mass spectrometer and by evaluating the mixing in the liquid phase with a pulse-shaped volatile tracer signal and mass spectrometer as a detector. The mean residence times and the intensities of the axial mixing in the riser and downcomer, the circulation times of the gas phase, and the fraction of the recirculated gas phase were evaluated and compared.