Development of an integrated process for the production of high-purity γ-aminobutyric acid from fermentation broth

γ-Aminobutyric acid (GABA), a natural non-protein amino acid, plays an irreplaceable role in regulating the life activities of organisms. Nowadays, the separation and purification of food-grade GABA from fermentation broth is still a great challenge. This research utilized monosodium glutamate as a substrate for the production of high-purity GABA via an integrated process incorporating fermentation, purification, and crystallization. Firstly, 147 g·L^-1 GABA with a yield of 99.8% was achieved through fed-batch fermentation by Lactobacillus brevis CE701. Secondly, three integrated purification methods by ethanol precipitation were compared, and crude GABA with a purity of 89.85% was obtained by the optimized method. Thirdly, GABA crystals with a purity of 98.69% and a yield of 60% were further obtained through a designed crystallization process. Furthermore, the GABA industrial production process model was established by Superproper Designer V10 software, and material balance and economic analysis were carried out. Ethanol used in the process was recovered with a recovery of 98.79% through Aspen simulated extractive distillation. Then the fixed investment (equipment purchase and installation costs) for an annual production of 80 t GABA will be about 833000 USD; the total annual production cost (raw material cost and utility cost) will be about 641000 USD. The annual sale of GABA may be at the range of 2400000-4000000 USD and the payback period will be about 1-2 year. This integrated process provides a potential way for the industrial-scale production of food-grade GABA.     

Statistical optimization of fermentation conditions for the improved production of poly-β-hydroxybutyrate from Bacillus subtilis

Poly-β-hydroxybutyrate (PHB) has been an effective biodegradable plastic obtained by microbial fermentation. Batch fermentation of Bacillus subtilis features an attractive system for the production of PHB. Identification of appropriate media components and cultivation conditions are extremely important for the optimal production of biomass and/or PHB production. Statistical media design was utilized for the optimization of different fermentation variables (glucose, peptone, sodium chloride, K₂HPO₄, KH₂PO₄, ammonium sulfate, ammonium chloride, sodium sulfate, temperature, inoculum size, and pH). The optimized media predicted the optimal dry cell weight of 7.54?g?L^?1 and PHB production of 77.2?mg?L^?1 at 1?g?L^?1 of peptone, 1.46?g?L^?1 sodium sulfate, and pH 6.8 in 24?h. Glucose utilization, batch growth, and PHB production kinetics of B. subtilis were determined experimentally. The effect of substrate inhibition on specific growth rate was also determined experimentally for B. subtilis. The values of kinetic and substrate inhibition parameters obtained from this study shall be utilized to develop a mathematical model for PHB production for further improving the production of PHB.     

Application of the “fusion” approach for the production of highly efficient biocatalysts based on recombinant strains of the fungus Penicillium verruculosum for the conversion of cellulose-containing biomass

Hydrolysis of cellulose-containing biomass mediated by biocatalysts (enzyme preparations, EP) is one of the most advanced and environmentally friendly methods of obtaining a range of useful substances. A new approach to creating recombinant EPs with predefined properties, which consists in applying fusion constructs for the cloning of genes encoding target enzymes, was used in the present study. A number of EPs with different properties was derived from a strain of the fungus Penicillium verruculosum using fusion constructs; these preparations are of interest primarily as additives enhancing the hydrolytic capacity of the basic cellulolytic complex from P. verruculosum. Use of the new EPs in combination with the basic EP from P. verruculosum resulted in an increase of the biocatalytic (hydrolytic) efficiency of the latter towards cellulose-containing raw materials of plant origin. Addition of 20% of the new EP to the basic EP without changing the total EP dose in the reaction mixture resulted in a significant (up to 70%) increase of the efficiency of hydrolysis of cellulose-containing substrates (ground aspen wood and shredded deresined pine wood).     

Process integration aspects for the production of fine chemicals illustrated with the biotransformation of γ-butyrobetaine into l-carnitine

l-carnitine is a fine chemical with pharmaceutical, nutritional and animal food applications. Thus, the product purification forms an essential part of the production process. Consequently, process optimization of biotransformation and downstream processing should be done in an integral way. There are several options for the process design of the biotransformation, e.g. chemostat with cell recycling, one-stage or multistage, fed-batch. Blackman kinetics for the product formation of the biotransformation of γ-butyrobetaine into l-carnitine provided adequate modelling of the bioprocess in order to define the optimal process design with respect to productivity, downstream processing and cost. With respect to these criteria, the fed-batch biotransformation of γ-butyrobetaine into l-carnitine appeared to be superior over several modes of operation of the continuous process with cell recycling. A lower productivity of the fed-batch process was compensated by a disproportionally cheaper downstream processing or a lower investment cost.Furthermore, process integration considerations determined the choice of raw materials for the biotransformation, such as carbon and nitrogen sources, resulting in optimized or even a reduced number of unit operations of the downstream processing.     

An integrated system of a microreactor with a Taylor–Couette reactor for 2,2′-dibenzothiazole disulfide synthesis

An integrated microreaction system of a microreactor with a Taylor–Couette reactor (TCR) for continuous synthesis of 2,2′-dibenzothiazole disulfide has been developed, so as to improve the process efficiency and the stability with solid product generation compared with the current batch process. The homogeneous oxidation with hydrogen peroxide catalyzed by phosphotungstic acid was applied. In the microreaction system, two feedstocks can be rapidly mixed through the microreactor; stable particle flow ability and high conversion can be achieved through the TCR, due to the flow characteristics of high shear stress and limited back-mixing. Under the conditions of stable operation, the conversion can reach over 90%. The purity of the product is over 99%. The space–time yield can reach 160 g L⁻¹ h⁻¹, which is much higher than that in the batch reactor. The microreaction system is stable for long-term running, which provides an effective design strategy for continuous flow processes with solid generation.     

Numerical solution of viscous flow past a solid sphere with the control volume formulation

The control volume formulation with the QUICK finite difference scheme is used to solveincompressible liquid flow past a solid sphere in terms of stream function and vorticity.Several tech-nical points are addressed on improving the accuracy and efficiency of numerical simulation of similarproblems of fluid flow.In particular,the importance of suitable specification of the distortion func-tion to enforcing the far field boundarv conditions is emphasized.     

Development and introduction of a highly efficient catalyst for the butane–butylene fraction oligomerization process for the production of a high-octane automobile gasoline compound

The main stages in developing a technology for the production of high-silica ZSM-5 zeolite-based catalyst for the butane–butylene fraction (BBF) oligomerization process are described. The application of a new zeolite surface modification procedure allows the attainment of higher selectivity and target product yields (compared to familiar analogs) and the synthesis of more branched (and thus more high-octane) oligomers at lower pressures. The introduction of promoting metal Ga raises the target gasoline fraction yield by 0.9%, compared to the unpromoted catalyst. Comparative pilot tests of industrial (BAK-70U) and the developed (Ga-ZSM-5/Al₂O₃) BBF oligomerization catalysts are performed under the following conditions: pressure, 1.5 MPa; initial working temperature, 300°C; feedstock hourly space velocity (FHSV), 1.5 mL BBF/(mL cat h). It is shown that using modified ZSM-5 based catalyst results in a gasoline fraction yield 7% higher than with BAK-70U. The higher quality of the oligomerizate obtained on Ga-ZSM-5/Al₂O₃ is observed throughout the period of tests (191 h): MON is 2 points higher, and the concentration of gums is 50% lower. The results from these studies and tests are used for the development and industrial implementation of a technology for the production of the KOB-1 zeolite oligomerization catalyst: 2.5 t of industrial catalyst has been produced by September of 2016 at the industrial facilities of ZAO Redkino Catalyst Plant. The next important stage in the implementation of the Gazprom Netf innovative development strategy in oil refining is a pilot run of the new oligomerization catalyst in the combined industrial MTBE–oligomerizate production plant of Gazprom Neft Moscow Oil Refinery. The introduction of the KOB-1 catalyst at the Gazprom Neft Oil Refinery will be an important step in improving the efficiency of technologies for the production of high-margin products, especially compounds of commercial automobile gasoline.     

Design and control of reactive distillation–recovery distillation flowsheet with a decanter for synthesis of N-propyl propionate

Reactive distillation (RD) for the synthesis of n-propyl propionate (ProPro) is operated with an excess of the reactant n-propyl alcohol (ProOH). It is simulated as a two-column system which can be easily controlled compared with a single reactive column which is operated neat, because the recovery column acts conceptually as a composition analyzer. The optimal steady-state design of the two-column system with the minimal total annual cost (TAC) is screened first. Then, an effective control scheme is established to handle feed disturbances. Only tray temperatures are required in the dynamic control two-column process. The product purity is held close to the set value 99.5 mol% and large deviation is prevented.     

Detonation combustion of a hydrogen–oxygen mixture in a plane–radial combustor with exhaustion toward the center

Regimes of continuous spin detonation in a plane–radial combustor with an external diameter of 80 mm with peripheral injection of a hydrogen–oxygen mixture in the range of specific flow rates of the mixture 3.6–37.9 kg/(s ·m²) are obtained for the first time. Depending on the diameter of the exit orifice in the combustor (40, 30, or 20 mm), specific flow rate of the mixture, its composition, and counterpressure, one to seven transverse detonation waves with a frequency from 6 to 60 kHz are observed. It is found that the number of detonation waves increases, while their intensity decreases owing to reduction of the exit orifice diameter or to an increase in the counterpressure. The flow structure in the region of detonation waves is analyzed. The domain of detonation regimes in the coordinates of the fuel-to-air equivalence ratio and specific flow rate of the mixture is constructed. A physicomathematical model of continuous spin detonation in a plane–radial combustor is formulated. For parameters of hydrogen and oxygen injection into the combustor identical to experimental conditions, the present simulations predict similar parameters of detonation waves, in particular, the number of waves over the combustor circumference and the wave velocity.     

Characteristics of non-platinum cathode catalysts for a hydrogen–oxygen fuel cell with proton- and anion-conducting electrolytes

Cathode catalysts for a hydrogen–oxygen fuel cell (FC) with proton-conducting (acidic) and anion-conducting (alkaline) electrolytes are synthesized via the pyrolysis of nitrogen-containing iron and cobalt complexes on the surfaces of highly disperse carbon materials. The catalysts are characterized by X-ray photoelectron spectroscopy (XPS) and tested under model conditions on a thin-layer disk electrode and as a part of a membrane electrode assembly of hydrogen–oxygen FCs. The properties of the CoFe/C system formed via the pyrolysis of macroheterocyclic cobalt and iron compounds on carbon materials (XC-72 soot and multiwall nanotubes (MNTs)) are described for the first time. According to XPS data, the surface of the CoFe/C catalytic systems is enriched with carbon (95.5 at %) and contains nitrogen (2 at %), oxygen (2 at %), and metals (0.5 at %). According to the results from electrochemical measurements under model conditions, the CoFe/MNT catalytic systems approaches 60% Pt/C (HiSPEC9100) commercial platinum catalyst according to their activity in the oxygen reduction reaction in an alkaline medium (0.5 M KOH). The half-wave potentials are 0.85 and 0.88 V for CoFe/MNT and 60% Pt/C (HiSPEC9100) catalysts, respectively. The maximum specific powers of hydrogen–oxygen FCs with anion-conducting electrolytes are 210 mW/cm² (60% Pt/C (HiSPEC9100) based cathode) and 180 mW/cm² (CoFe/MNT based cathode). The characteristics of a membrane electrode assembly with a non-platinum cathode correspond to the best analogs described in the literature. The results of this work show the prospects for further studies on scaling this technology for the synthesis of the proposed non-platinum cathode catalysts and optimizing the architecture of the membrane electrode assembly of FCs based on them.     

3D-TEM investigation of the nanostructure of a δ-Al2O3 catalyst support decorated with Pd nanoparticles

The electron tomography technique applied in a quantitative way allowed us to characterize a heterogeneous catalyst made of Pd nanoparticles deposited on a δ-Al(2)O(3) lamellar support. In the first step, high resolution tomographic experiments carried out on several typical areas of support have confirmed the hypothesis of formation of δ-Al(2)O(3) proposed in the literature by the coalescence of lateral facets of the γ-Al(2)O(3) precursor. A bimodal porosity was also observed in the arrangement of δ-Al(2)O(3) platelets. In the second step, the Pd nanoparticles were found preferentially anchored on the lateral facets of δ-Al(2)O(3) platelets or on the defects situated on their basal planes. From a general point of view, we have demonstrated once again that the electron tomography technique implemented with nanometre resolution provides unique insight into the structure, morphology and spatial arrangement of components in a complex 3D nanostructure.     

An efficient reduction route for the production of Pd–Pt nanoparticles anchored on graphene nanosheets for use as durable oxygen reduction electrocatalysts

Pt and Pd–Pt nanoparticles were anchored on reduced graphene oxide (RGO) with the aid of poly(diallyldimethylammonium chloride) (PDDA), where Pt and Pd ions were first attached to PDDA-functionalized graphene oxide sheets and the encased metal ions and graphene oxide were then reduced simultaneously by ethylene glycol. As supported by transmission electron microscopy, metal nanoparticles, of small particle size even at a high metal loading, were chemically attached to PDDA–RGO. X-ray diffraction indicates that the as-prepared Pd–Pt nanoparticles have a single-phase fcc structure and are principally alloys of Pd and Pt. Among the RGO-supported Pt and Pd–Pt catalysts, Pt nanoparticles anchored on PDDA–RGO exhibit the highest activity for the oxygen reduction reaction (ORR), and the ORR activity of the Pd–Pt alloy electrocatalysts increases with Pt content. All the catalysts demonstrate an enhanced ORR durability when PDDA is present; strongly suggesting that PDDA plays a crucial role in the dispersion and stabilization of the metal nanoparticles on RGO. The ORR activities of the Pd–Pt catalysts remain enhanced even after accelerated durability testing. The formation of a Pt-rich shell, as confirmed by X-ray photoelectron spectroscopy and CO stripping voltammetry, may account for the increased activity.     

Development of a green integrated process for biodiesel esters production: Use of fermented macaúba cake as biocatalyst for macaúba acid oil transesterification

In this study, a new green integrated process for biodiesel ester production was developed, consisting of the enzymatic transesterification of acid oil from macaúba palm tree (Acrocomia aculeata) catalyzed by dry fermented solid (DFS) with lipase activity, which was obtained from solid-state fermentation (SSF) of macaúba cake. Analysis of statistical experimental designs showed that nitrogen supplementation of macaúba cake improved production of lipases displaying esterification capacity by Rhizomucor miehei. The conditions chosen to produce R. miehei DFS were cake supplementation with 2 wt% urea, 60 wt% of initial moisture during 48 h of fermentation at 40°C. DFS showed, by zymography assays, at least one enzyme that was different from those that are present in the commercial lipase of R. miehei. Furthermore, DFS was used in transesterification reactions between macaúba acid oil and alcohol (methanol or ethanol), and the ester content obtained was 92%. This is the first time that this integrated process using low-cost biocatalysts and a low-value oil derived from the processing of the same fruit was used for biodiesel ester production, reducing costs and logistic constraints, and optimizing the raw material utilization.     

Thermally stable alumina–gallia aerogel as a catalyst for NO reduction with C3H6 in the presence of excess oxygen

In order to improve thermal stability, an alumina–gallia aerogel was prepared and the catalyst performance for NO reduction with C₃H₆ was compared with that of an alumina–gallia xerogel. Basically, both were prepared by a sol–gel method with supercritical drying for the former, while with oven drying for the latter. Upon heating at 800, 900, and 1000°C, the aerogel exhibited higher NO conversion than the xerogel at reaction temperature <400°C, while NO conversion was lower on the former than on the latter at >500°C. At 450°C, NO conversion was almost the same for these two catalysts. A marked difference was observed upon heating them at 1100°C: the aerogel still maintained quite a high activity, while the xerogel greatly lost it. After heating the aerogel at 1100°C, -phase alumina remained untransformed with its surface area of 80 m²/g, while the xerogel was completely transformed to -alumina with its surface area of 6 m²/g. The high activity remaining on the aerogel heated at 1100°C was ascribed to its large surface area.     

Use of dry yeast cells as a cheap nitrogen source for lactic acid production by thermophilic Bacillus coagulans WCP10-4? ?

Dry yeast cells (DYC) were used as a cheap nitrogen source to replace expensive yeast extract (YE) for L-lactic acid production by thermophilic Bacillus coagulans. Cassava starch (200 g·L⁻¹) was converted to L-lactic acid by simultaneous saccharification and fermentation using Bacillus coagulans WCP10-4 at 50 °C in the presence of 20 g·L⁻¹ of DYC, giving 148.1 g·L⁻¹ of L-lactic acid at 27 h with a productivity of 5.5 g·L⁻¹·h⁻¹ and a yield of 92%. In contrast, 154.4 g·L⁻¹ of lactic acid was produced at 24 h with a productivity of 6.4 g·L⁻¹·h⁻¹ and a yield of 96% when equal amount of YE was used under the same conditions. Use of pre-autolyzed DYC at 50 °C for overnight slightly improved the lactic acid titer (154.5 g·L⁻¹) and productivity (7.7 g·L⁻¹·h⁻¹) but gave the same yield (96%).     

Functionalized metal–organic frameworks with strong acidity and hydrophobicity as an efficient catalyst for the production of 5-hydroxymethylfurfural

In the dehydration of fructose to 5-hydroxymethyl furfural(HMF), in situ produced water weakens the acid strength of the catalyst and causes the rehydration of HMF, causing unsatisfactory catalytic activity and selectivity. In this work, a class of benzenesulfonic acid-grafted metal–organic frameworks with strong acidity and hydrophobicity is obtained by the direct sulfonation method using 4-chlorobenzenesulfonic acid as sulfonating agent. The resultant MOFs have a specific surface area of greater than 250 m~2·g~(-1), acid density above 1.0 mmol·g~(-1), and water contact angle up to 129°. The hydrophobic MOF-Ph SO_3 H exhibits both higher catalytic activity and selectivity than MOF-SO_3 H in the HMF synthesis due to its better hydrophobicity and olephilicity. Moreover, the catalyst has a high recycled stability. At last, fructose is completely converted, and 98.0% yield of HMF is obtained under 120 °C in a DMSO solvent system. The successful preparation of the hydrophobic acidic MOF provides a novel hydrophobic catalyst for the synthesis of HMF.     

Investigation of Mixtures of a Co-Based Catalyst and a Cu-Based Catalyst for the Fischer–Tropsch Synthesis with Bio-Syngas: The Importance of Indigenous Water

A series of different mechanical mixtures of a narrow-pore Co/γ-Al₂O₃ catalyst and a Cu-based WGS-catalyst has been investigated in the low-temperature Fischer–Tropsch synthesis (483 K, 20 bar) with a model bio-syngas (H₂/CO = 1.0) in a fixed-bed reactor. The higher the fraction of WGS-catalyst in the mixture, the lower is the Co-catalyst-time yield to hydrocarbons. This is ascribed to a strong positive kinetic effect of water on the Fischer–Tropsch rate of the Co-catalyst, showing the importance of the indigenously produced water, especially in fixed-bed reactors where the partial pressure of water is zero at the reactor inlet. A preliminary kinetic modeling suggests that the reaction order in P $ _{{{\text{H}}_{ 2} {\text{O}}}} $ is 0.3 for the Co/γ-Al₂O₃ catalyst in the range of the studied reactor-average partial pressures of water (i.e., 0.04–1.2 bar).     

Direct computation of the performance of sequential procedures based on a sequence of t-statistics,with application to a confidence interval for μ/σ in a normal population

Formulas are derived for the direct computation — as opposed to simulation or approximation — of sequential procedures that are based on a sequence of t-statistics. This is applied to the numerical computation of the performance of a one-sided confidence interval for γ = μ/σ in a normal population, when the probability of covering the true value γ as well as the probability of covering the false value γ ? d, for given d > 0,is specified.