Recycle Membrane Reactor Research Articles

Green ammonia production via recycle membrane reactor: Experiment and process simulation

With the increasing demand for ammonia (NH3) and the environmental benefits, green and sustainable NH3 production has been urgently developed and is expected to replace the traditional Haber-Bosch (HB) process with high energy consumption and COx emission. In this work, a recycle membrane reactor (RMR) process where a catalytic reactor relates to a membrane separator in series and the retentate stream is recycled to the reactor was designed and executed to produce NH3, in which a Ru (10 wt%)/Cs/MgO catalyst and two membranes with different permeation properties and NH3 selectivity were used. By independently controlling the temperature of the reactor and membrane separator, the synthesized NH3 was selectively extracted from feed side to permeate side by Aquivion/ceramic composite and sulfonated (3-mercaptopropyl)trimethoxysilane membranes. Impressively, NH3 mole fraction was greatly increased from 0.01 of equilibrium state to 0.1–0.45 in permeate stream, which is ascribed to the permeation properties and NH3 selectivity of membrane at different temperatures. Moreover, a one-dimensional, isothermal, and plug-flow model was proposed to simulate RMR, which can be successfully applied to deeply understand the mechanism of RMR. Furthermore, a green NH3 production process based on RMR was simulated to give rationalized suggestions for the NH3 synthesis under mild conditions.

Genetically engineered Escherichia coli FBR5: Part I. Comparison of high cell density bioreactors for enhanced ethanol production from xylose

Five reactor systems (free cell batch, free cell continuous, entrapped cell immobilized, adsorbed cell packed bed, and cell recycle membrane reactors) were compared for ethanol production from xylose using Escherichia coli FBR5. In the free cell batch and free cell continuous reactors (continuous stirred tank reactor-CSTR) productivities of 0.84 gL(-1) h(-1) and 1.77 gL(-1) h(-1) were achieved, respectively. A cell recycle membrane reactor resulted in the highest productivity of 55.56 gL(-1) h(-1), which is an increase of 66-fold (e.g., 6614%) over the batch reactor. Calcium alginate gel CSTR resulted in a productivity of 2.04 gL(-1) h(-1) whereas adsorbed cell packed bed reactor resulted in a productivity of 4.39 gL(-1) h(-1). In the five reactor systems, ethanol concentrations ranged from 18.9 to 40.30 gL(-1) with metabolic yields from 0.44 to 0.51.

A Comparative Study on the Production of Galacto-oligosaccharide from Whey Permeate in Recycle Membrane Reactor and in Enzymatic Batch Reactor

The present study primarily is an attempt to establish a technique on the disposal scheme for the wastewater coming out as an effluent from milk industries with proper environmental guides and regulations. Apart from the wastewater treatment methodology development, the present work mainly focuses on the attainment of high value product, such as the production of galactosyl-oligosaccharide (GOS) in batch reactor and as well as in recycle membrane reactor after hydrolyzing recovered lactose from the whey stream with β-galactosidase enzyme originated, from Bacillus circulans. Around 77−78% purity of this GOS was achieved with three-step membrane separation techniques: the first one was the ultrafiltration followed by diafiltration equipped nanofiltration. In recycle membrane reactor, GOS production was found to be 33% higher than that in the batch reactor, and monosaccharide concentration was 78% lower with 23% remaining enzyme activity after 18,000 s of reaction time.

Increasing the efficiency of the enzymatic hydrolysis of potato starch in a membrane reactor

The aim of the work was to define the physicochemical parameters of a reaction system that alter the effectiveness of a continuous recycle membrane reactor during potato starch hydrolysis. The enzymatic hydrolysis of starch in an ultrafiltration reaction system proceeded with a continuous decrease in the permeate flux, accompanied by an increase in dry substance content in both the permeate and retentate fractions. The decrease in the permeate flux was caused by an increase in feed viscosity. If a prehydrolysis process was conducted, it was possible to enzymatically hydrolyse potato starch in solutions with concentrations up to 20%. A quasi-steady state of starch enzymatic hydrolysis was reached in the ultrafiltration reaction system by alternately supplementing it with starch solution and water.

The influence of types of dual modified starches on the enzymatic hydrolysis in the continuous recycle membrane reactor

The aim of work was to study the influence of the degree of substitution of acetylated oxidized starch (E-1451) on the process of enzymatic hydrolysis in a continuous recycle membrane reactor (CRMR). Three kinds of E-1451 starch preparations with different degrees of carboxyl group substitution (0.04, 0.11 and 0.5%) and with different degrees of acetylation: 0.5% and 2.5% (3%) were examined. The waxy corn modified starch was also investigated. Hydrolyses were performed in the CRMR equipped with an ultrafiltration module containing a ceramic membrane of tubular configuration. The membranes used were characterised by the following parameters: a length of 0.3 m, external diameter of 10 mm, three channels and a molecular weight cut-off of 50, 15 or 8 kDa. During the process the UF module was working in three variants: with a membrane of 15 kDa or a set of two membranes: 50/15 kDa and 15/8 kDa. The hydrolysis process was performed over a period of 150 min at a temperature of 60°C, at the transmembrane pressure of 0.5 MPa and with a 0.3 ml of enzyme preparation BAN 480 L per 1 kg of dry starch. It was stated that the efficiency of the separation process as well as the effectiveness of hydrolysis process was affected by the type of modification and the degree of substitution of starch.

Continuous recycle membrane reactor for enzymatic hydrolysis of dual modified potato starch

The chemically modified starches, and their hydrolysates were developed with broad application in the food, paper and textile industries because of their capacities for emulsifying various colloidal emulsions. One of the methods of making starch hydrolysates is conducting an enzymatic reaction in a continuous recycle membrane reactor (CRMR). The introduction of the membrane reactor makes it possible to conduct the enzymatic hydrolysis process more economically by reusage of enzymes to increase the reaction yield, shorten the reaction time and reduce costs. The aim of the present research was selection of optimal work conditions for enzymatic hydrolysis of dual modified potato starch in a CRMR with an outer ultrafiltration (UF) module (CRMR). Two different variants of courses of the hydrolysis process were investigated. Materials for investigations were dual modified potato starches (by oxidation and acetylation), with the various content of acetyl groups. BAN 480 L, which contains amylase of bacterial origin, was used as an enzymatic preparation. The measure of hydrolysis productivity was a change of dry substance (DS) in the filtrate fraction, while the measure of its efficiency was the obtained degree equivalent (DE) of hydrolyzed derivative.

Physicochemical properties of cross-linked and acetylated starches and products of their hydrolysis in continuous recycle membrane reactor

The aim of the present work was to study the physicochemical properties of doubly modified, by cross-linking and acetylating, starches as well as the products of their enzymatic hydrolysis. A two step procedure of hydrolysis, including the batch and membrane reactors, were investigated. The second step of enzymatic processes were carried out in a continuous recycle membrane reactor (CRMR). Three kinds of commercial starches – two preparations of acetylated distarch adipate E1422 of different degrees of cross-linking, as well as one preparation of acetylated distarch phosphate E1414 were examined. It was found that the degree of substitution of acetyl groups in the macromolecules of starch did not influence the effectiveness of hydrolysis. However, the degree of cross-linking with adipate groups slightly decreased the efficiency of processing in the CRMR. Additionally, the relationship between the type of hydrocolloid and its adsorption activity in the air/water and oil/water systems was considered. All obtained derivatives revealed adsorption properties and reduced the surface/interface tension in the air/water and oil/water systems. The efficiency and effectiveness of adsorption of the investigated hydrocolloids were affected by the type of modification as well as the degree of substitution of acetyl groups in the macromolecules of starch. Particle size distributions formed in aqueous solutions for all investigated hydrolyses were determined and compared with results obtained for commercial products.

Salt stress effects on the central and carnitine metabolisms of Escherichia coli

The aim was to understand how interaction of the central carbon and the secondary carnitine metabolisms is affected under salt stress and its effect on the production of L-carnitine by Escherichia coli. The biotransformation of crotonobetaine into L-carnitine by resting cells of E. coli O44 K74 was improved by salt stress, a yield of nearly twofold that for the control being obtained with 0.5 M NaCl. Crotonobetaine and the L-carnitine formed acted as an osmoprotectant during cell growth and biotransformation in the presence of NaCl. The enzyme activities involved in the biotransformation process (crotonobetaine hydration reaction and crotonobetaine reduction reaction), in the synthesis of acetyl-CoA/acetate (pyruvate dehydrogenase, acetyl-CoA synthetase [ACS] and ATP/acetate phosphotransferase) and in the distribution of metabolites for the tricarboxylic acid cycle (isocitrate dehydrogenase [ICDH]) and glyoxylate shunt (isocitrate lyase [ICL]) were followed in batch with resting cells both in the presence and absence of NaCl and in perturbation experiments performed on growing cells in a high density cell recycle membrane reactor. Further, the levels of carnitine, crotonobetaine, gamma-butyrobetaine and ATP and the NADH/NAD(+) ratio were measured in order to know how the metabolic state was modified and coenzyme pools redistributed as a result of NaCl's effect on the energy content of the cell. The results provided the first experimental evidence of the important role played by salt stress during resting and growing cell biotransformation (0.5 M NaCl increased the L-carnitine production in nearly 85%), and the need for high levels of ATP to maintain metabolite transport and biotransformation. Moreover, the main metabolic pathways and carbon flow operating during cell biotransformation was that controlled by the ICDH/ICL ratio, which decreased from 8.0 to 2.5, and the phosphotransferase/ACS ratio, which increased from 2.1 to 5.2, after a NaCl pulse fivefold the steady-state level. Resting E. coli cells were seen to be made up of heterogeneous populations consisting of several types of subpopulation (intact, depolarized, and permeabilized cells) differing in viability and metabolic activity as biotransformation run-time and the NaCl concentration increased. The results are discussed in relation with the general stress response of E. coli, which alters the NADH/NAD(+) ratio, ATP content, and central carbon enzyme activities.

An attempt to application of continuous recycle membrane reactor for hydrolysis of oxidised derivatives of potato starch

Oxidised starches E 1404 are the most popular food grade modified starches but the process of their enzymatic hydrolysis was not investigated, and the functionality of the products of this processing is unknown. The aim of the work was to study the possibility of the application of continuous recycle membrane reactor (CRMR) for the hydrolysis of oxidised starches as well as the estimation of the surface properties of the obtained products. It was found that the application of CRMR for the enzymatic hydrolysis of oxidised starches allowed products to be obtained which reveal surface activity. The effectiveness of the membrane process is strongly influenced by the rheological properties of the raw material, which determines fouling phenomena in reaction system. The presence of carboxyl groups in starch macromolecules did not inhibit their enzymatic hydrolysis. The surface properties of enzymatic hydrolysis products do not depend on the degree of oxidation of the investigated starches. Substantial differences of the surface activity for the permeate and retentate fractions were observed.

The effect of enzyme concentration and space time on the performance of a continuous recycle membrane reactor for one-step starch hydrolysis

In spite of minor limitations due to membrane fouling and catalyst inactivation, one-step hydrolysis of starch with termamyl enzyme in a continuous recycle membrane reactor appears to be a promising way to produce high DE sugar syrups. In addition to the main advantage over batch process to correctly integrating reaction and separation, this type of system opens up to process engineer tunable performance in terms of conversion, capacity and productivity. In this paper the effects of enzyme concentration and space time have been examined. As a whole it appears that by increasing these two parameters the conversion is improved; but the capacity and productivity are reduced leading to higher processing costs. Optimisation of enzyme concentration and space time needs that economic criteria are very carefully taken into account.

Why on Earth Can People Need Continuous Recycle Membrane Reactors for Starch Hydrolysis?

Classically enzymatic hydrolysis of starch is conducted in batch reactor in a two-step process including liquefaction and saccharification. This paper presents some ideas to simplify this process and decrease its cost. Because today, either saccharifying enzymes able to attack native starch or strong liquefying catalysts leading to sufficient low-molecular weight hydrolysates may be easily found on the market, one can imagine to develop a one-step process just involving a unique species of enzymes. The process can also be improved by operating in a continuous way and reusing enzymes. Among the various reactors, the continuous recycle membrane reactor, briefly CRMR, seems to be the most attractive since it allows to perform hydrolysis while separating at the same time syrups from enzymes and non-hydrolyzed starch. (Resume d'auteur)

Extractive ethanol production in a membrane cell recycle bioreactor

Ethanol production kinetics of free Saccharomyces cerevisiae cells was compared in a continuous reactor and a cell recycle membrane reactor, with and without solvent extraction. In the continuous culture the in-situ extraction using dibutyl phthalate increased glucose conversion from 45% to 91%, the cell concentration from 10.2 g l −1 to 23.6 g l −1 and the ethanol productivity from 8.2 g l −1 h −1 to 20 g l −1 h −1 when a 270 g l −1 glucose solution was fed to the reactor at a dilution rate of 0.16 h −1. In the membrane cell recycle culture with the solvent extraction the ethanol productivity increased to 45 g l −1 h −1 and 70% of the ethanol produced was extracted to the solvent stream. The mathematical modeling of the extractive bioconversion predicted ethanol concentration and productivity of the system reasonably well.