scholarly journals The Immobilization of Lipases on Porous Support by Adsorption and Hydrophobic Interaction Method

Catalysts ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 744
Author(s):  
Nur Fathiah Mokhtar ◽  
Raja Noor Zaliha Raja Abd. Rahman ◽  
Noor Dina Muhd Noor ◽  
Fairolniza Mohd Shariff ◽  
Mohd Shukuri Mohamad Ali
Keyword(s):  
Ph Value ◽  
Continuous Process ◽  
Immobilized Enzymes ◽  
Industrial Applications ◽  
Adsorption Method ◽  
Porous Support ◽  
Microbial Lipases ◽  
The Stability ◽  
The Cost ◽  
Hydrophobic Supports

Four major enzymes commonly used in the market are lipases, proteases, amylases, and cellulases. For instance, in both academic and industrial levels, microbial lipases have been well studied for industrial and biotechnological applications compared to others. Immobilization is done to minimize the cost. The improvement of enzyme properties enables the reusability of enzymes and facilitates enzymes used in a continuous process. Immobilized enzymes are enzymes physically confined in a particularly defined region with retention to their catalytic activities. Immobilized enzymes can be used repeatedly compared to free enzymes, which are unable to catalyze reactions continuously in the system. Immobilization also provides a higher pH value and thermal stability for enzymes toward synthesis. The main parameter influencing the immobilization is the support used to immobilize the enzyme. The support should have a large surface area, high rigidity, suitable shape and particle size, reusability, and resistance to microbial attachment, which will enhance the stability of the enzyme. The diffusion of the substrate in the carrier is more favorable on hydrophobic supports instead of hydrophilic supports. The methods used for enzyme immobilization also play a crucial role in immobilization performance. The combination of immobilization methods will increase the binding force between enzymes and the support, thus reducing the leakage of the enzymes from the support. The adsorption of lipase on a hydrophobic support causes the interfacial activation of lipase during immobilization. The adsorption method also causes less or no change in enzyme conformation, especially on the active site of the enzyme. Thus, this method is the most used in the immobilization process for industrial applications.

Designing an optimal controller for rectangular natural circulation loops

2003 ◽  
Vol 217 (3) ◽  
pp. 171-180 ◽  
Author(s):  
L Cammarata ◽  
A Fichera ◽  
A Pagano
Keyword(s):  
Natural Circulation ◽  
Industrial Applications ◽  
Dynamical Behaviour ◽  
Heat Fluxes ◽  
Optimal Controller ◽  
Control Law ◽  
High Heating Rate ◽  
The Stability ◽  
The Cost ◽  
Flow Reversals

Controlling the dynamics of natural circulation loops represents a major task for the widespread use of this kind of system in safe industrial applications. This paper aims to design an innovative model-based optimal controller for the suppression of unstable oscillations and flow reversals, which affect the dynamical behaviour of a closed-loop thermosyphon at high heating rate. The key idea is to define a multivariable control law aiming to minimize an objective function taking into account both the stability of the system and the cost of control. The design of the proposed controller has been based on a model approximating to the first three modes of the dynamics of rectangular circulation loops with imposed heat fluxes at the boundaries. The capability of the proposed controller in suppressing undesired dynamics has been experimentally demonstrated.

Sugar hydrolysis and colour formation in processing

2020 ◽  
pp. 540-548
Author(s):  
Jan Maarten de Bruijn
Keyword(s):  
Ph Value ◽  
Cost Effective ◽  
Production Costs ◽  
Ph Values ◽  
Technological Impact ◽  
The Stability ◽  
The Cost ◽  
Required Quality ◽  
White Sugar ◽  
Sugar Hydrolysis

The stability of the sucrose molecule throughout processing is of the utmost importance, because in principle any sugar loss will increase the production costs per tonne of the obtained white sugar. Colour in processing is an important technological parameter too, since only an adequate colour control in processing allows the cost-effective production of white sugar crystals of the required quality. For process control of both sugar hydrolysis and colour formation it is necessary to understand the effect of pH value, temperature and retention time on these phenomena. This paper will describe the possible causes of sugar hydrolysis and colour, as well as how to control pH values and temperature in processing in order to limit the technological impact of both reactions in which invert sugar plays a central role.

Influence of temperature and pH value on deposition rate and corrosion resistance of Ni–Zn–P alloy coating

2019 ◽  
Vol 33 (01n03) ◽  
pp. 1940013
Author(s):  
Yongfeng Li ◽  
Chengguo Fu ◽  
Lili Liu ◽  
Mingchao Liang ◽  
Yaming Liu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Deposition Rate ◽  
Ph Value ◽  
Chemical Properties ◽  
Alloy Coating ◽  
Industrial Applications ◽  
Complexing Agent ◽  
Solution Ph ◽  
Plating Bath ◽  
The Stability

The Ni–Zn–P alloy coating has excellent physical and chemical properties that have been exploited for various industrial applications. Using sodium citrate as a complexing agent and lactic acid as a stabilizer, the effects of temperature and pH on the deposition rate and corrosion resistance of electroless plated Ni–Zn–P coating were studied. The results indicated that, when the temperature was 85[Formula: see text]C, a good deposition rate was obtained with stable plating solution. pH value of 9.0 is preferred for the coating process by considering the stability of plating bath and deposition rate. The Ni–Zn–P alloy coating deposited with plating temperature of 85[Formula: see text]C and bath pH of 9.0 has good quality, and a uniform and smooth surface texture without porosity.

scholarly journals Black Hole Algorithm for Sustainable Design of Counterfort Retaining Walls

2020 ◽  
Vol 12 (7) ◽  
pp. 2767 ◽  
Author(s):  
Víctor Yepes ◽  
José V. Martí ◽  
José García
Keyword(s):  
Black Hole ◽  
Sustainable Design ◽  
Retaining Walls ◽  
The Other ◽  
Trade Off ◽  
Construction Company ◽  
Geometric Variables ◽  
The Stability ◽  
The Cost ◽  
Black Hole Algorithm

The optimization of the cost and CO 2 emissions in earth-retaining walls is of relevance, since these structures are often used in civil engineering. The optimization of costs is essential for the competitiveness of the construction company, and the optimization of emissions is relevant in the environmental impact of construction. To address the optimization, black hole metaheuristics were used, along with a discretization mechanism based on min–max normalization. The stability of the algorithm was evaluated with respect to the solutions obtained; the steel and concrete values obtained in both optimizations were analyzed. Additionally, the geometric variables of the structure were compared. Finally, the results obtained were compared with another algorithm that solved the problem. The results show that there is a trade-off between the use of steel and concrete. The solutions that minimize CO 2 emissions prefer the use of concrete instead of those that optimize the cost. On the other hand, when comparing the geometric variables, it is seen that most remain similar in both optimizations except for the distance between buttresses. When comparing with another algorithm, the results show a good performance in optimization using the black hole algorithm.

scholarly journals Solubility Data of Potential Salts in the MgO-CaO-SO2-H2O-O2 System for Process Modeling

Processes ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 50
Author(s):  
Barbara D. Weiß ◽  
Michael Harasek
Keyword(s):  
Process Modeling ◽  
Ph Value ◽  
Process Models ◽  
Solubility Data ◽  
Solid Base ◽  
International Union ◽  
The Stability ◽  
Experimental Values ◽  
So2 Absorption ◽  
Reliable Basis

This review studies unwanted precipitation reactions, which can occur in SO2 absorption processes using a magnesium hydroxide slurry. Solubility data of potential salts in the MgO-CaO-SO2-H2O system are evaluated. The reviewed data can serve as a reliable basis for process modeling of this system used to support the optimization of the SO2 absorption process. This study includes the solubility data of MgSO3, MgSO4, Mg(OH)2, CaSO3, CaSO4, and Ca(OH)2 as potential salts. The solubility is strongly dependent on the state of the precipitated salts. Therefore, this review includes studies on the stability of different forms of the salts under different conditions. The solubility data in water over temperature serve as a base for modeling the precipitation in such system. Furthermore, influencing factors such as pH value, SO2 content and the co-existence of other salts are included and available data on such dependencies are reviewed. Literature data evaluated by the International Union of Pure and Applied Chemistry (IUPAC) are revisited and additional and newer studies are supplemented to obtain a solid base of accurate experimental values. For temperatures higher than 100 °C the available data are scarce. For a temperature range from 0 to 100 °C, the reviewed investigations and data provide a good base to evaluate and adapt process models for processes in order to map precipitations issues accurately.

scholarly journals The stability of pH value in the waters of Jiaozhou Bay

2021 ◽  
Vol 829 (1) ◽  
pp. 012021
Author(s):  
Dongfang Yang ◽  
Danfeng Yang ◽  
Haixia Li ◽  
Dong Lin ◽  
Qi Wang
Keyword(s):  
Ph Value ◽  
Jiaozhou Bay ◽  
The Stability

Studies on the Coordination Reaction of VO2+ and Tannic Acid in the Tannin Extract Desulfurization

2012 ◽  
Vol 239-240 ◽  
pp. 1573-1576
Author(s):  
Zhu Qing Gao ◽  
Xiao Dong Cai ◽  
Kai Cheng Ling
Keyword(s):  
Stability Constants ◽  
Tannic Acid ◽  
Ph Value ◽  
Protonation Constants ◽  
Conditional Stability ◽  
Tannin Extract ◽  
Acid Effect ◽  
Different Temperatures ◽  
The Stability ◽  
Apparent Stability

At different temperatures, the protonation constants of tannic acid and the complex apparent stability constants between tannic acid and VO2+ were determined by using pH potentimetric method. The results showed that the protonation constants and the complex apparent stability constants slightly decreased with the raising temperature. In accordance with the pH value in the tannin extract technology, the conditional stability constants of the complex were calculated on the basis of the acid effect of tannic acid and the hydrolysis effect of VO2+. It was found that pH greatly affected the stability constants of the complex , so pH must be strictly controlled in the tannin extract technology.

scholarly journals Suboptimal Disturbance Observer Design Using All Stabilizing Q Filter for Precise Tracking Control

Mathematics ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1434 ◽  
Author(s):  
Wonhee Kim ◽  
Sangmin Suh
Keyword(s):  
Design Method ◽  
Industrial Applications ◽  
Point Of View ◽  
Observer Design ◽  
Linear Matrix ◽  
External Disturbances ◽  
Closed Loop Systems ◽  
Control Target ◽  
The Stability ◽  
Unified Index

For several decades, disturbance observers (DOs) have been widely utilized to enhance tracking performance by reducing external disturbances in different industrial applications. However, although a DO is a verified control structure, a conventional DO does not guarantee stability. This paper proposes a stability-guaranteed design method, while maintaining the DO structure. The proposed design method uses a linear matrix inequality (LMI)-based H∞ control because the LMI-based control guarantees the stability of closed loop systems. However, applying the DO design to the LMI framework is not trivial because there are two control targets, whereas the standard LMI stabilizes a single control target. In this study, the problem is first resolved by building a single fictitious model because the two models are serial and can be considered as a single model from the Q-filter point of view. Using the proposed design framework, all-stabilizing Q filters are calculated. In addition, for the stability and robustness of the DO, two metrics are proposed to quantify the stability and robustness and combined into a single unified index to satisfy both metrics. Based on an application example, it is verified that the proposed method is effective, with a performance improvement of 10.8%.

scholarly journals Longevity of Raw and Lyophilized Crude Urease Extracts

2021 ◽  
Vol 2 (2) ◽  
pp. 325-334
Author(s):  
Neda Javadi ◽  
Hamed Khodadadi Tirkolaei ◽  
Nasser Hamdan ◽  
Edward Kavazanjian
Keyword(s):  
Crude Extract ◽  
Room Temperature ◽  
Low Cost ◽  
Extraction Process ◽  
Crude Extracts ◽  
Simple Extraction ◽  
Commercial Applications ◽  
Stable Source ◽  
The Stability ◽  
The Cost

The stability (longevity of activity) of three crude urease extracts was evaluated in a laboratory study as part of an effort to reduce the cost of urease for applications that do not require high purity enzyme. A low-cost, stable source of urease will greatly facilitate engineering applications of urease such as biocementation of soil. Inexpensive crude extracts of urease have been shown to be effective at hydrolyzing urea for carbonate precipitation. However, some studies have suggested that the activity of a crude extract may decrease with time, limiting the potential for its mass production for commercial applications. The stability of crude urease extracts shown to be effective for biocementation was studied. The crude extracts were obtained from jack beans via a simple extraction process, stored at room temperature and at 4 ℃, and periodically tested to evaluate their stability. To facilitate storage and transportation of the extracted enzyme, the longevity of the enzyme following freeze drying (lyophilization) to reduce the crude extract to a powder and subsequent re-hydration into an aqueous solution was evaluated. In an attempt to improve the shelf life of the lyophilized extract, dextran and sucrose were added during lyophilization. The stability of purified commercial urease following rehydration was also investigated. Results of the laboratory tests showed that the lyophilized crude extract maintained its activity during storage more effectively than either the crude extract solution or the rehydrated commercial urease. While incorporating 2% dextran (w/v) prior to lyophilization of the crude extract increased the overall enzymatic activity, it did not enhance the stability of the urease during storage.

scholarly journals Competing Conventions with Costly Information Acquisition

Games ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 53
Author(s):  
Roberto Rozzi
Keyword(s):  
Information Acquisition ◽  
Evolutionary Model ◽  
Equilibrium Selection ◽  
The Other ◽  
Group Interactions ◽  
Social Coordination ◽  
Long Run ◽  
Stochastic Stability Analysis ◽  
The Stability ◽  
The Cost

We consider an evolutionary model of social coordination in a 2 × 2 game where two groups of players prefer to coordinate on different actions. Players can pay a cost to learn their opponent’s group: if they pay it, they can condition their actions concerning the groups. We assess the stability of outcomes in the long run using stochastic stability analysis. We find that three elements matter for the equilibrium selection: the group size, the strength of preferences, and the information’s cost. If the cost is too high, players never learn the group of their opponents in the long run. If one group is stronger in preferences for its favorite action than the other, or its size is sufficiently large compared to the other group, every player plays that group’s favorite action. If both groups are strong enough in preferences, or if none of the groups’ sizes is large enough, players play their favorite actions and miscoordinate in inter-group interactions. Lower levels of the cost favor coordination. Indeed, when the cost is low, in inside-group interactions, players always coordinate on their favorite action, while in inter-group interactions, they coordinate on the favorite action of the group that is stronger in preferences or large enough.

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