Stabilization of recombinant d-Lactate dehydrogenase enzyme with trehalose: Response surface methodology and molecular dynamics simulation study

The effects of dextran in residual impurity on trehalose crystallization and formula in food preservation

The residual dextran impurities in the upstream process significantly impact the crystallization of starch-based functional sugar and the related food properties. This study intends to reveal the mechanism of dextran's influence on trehalose crystallization, and build a relationship among the dextran in syrup and the physicochemical and functional properties of trehalose. Instead of incorporating into the crystal lattice, dextran changes the assembly rate of trehalose molecules on crystal surface. The different sensitivity and adsorption capacity of the crystal surface to the chain length of dextran determines the growth rate of crystal surfaces, resulting in different crystal morphology. The bulk trehalose crystals, which were obtained from syrups with short chain dextran, have excellent powder properties, including best flowability (35◦), highest crystal strength (2.7 N), lowest caking rate (62.22 %), and the most uniform mixing with other sweeteners (sucrose/xylitol) in food formulations, achieving more stable starch preservation.

Exploring the impact of taurine on the biochemical properties of urate oxidase: response surface methodology and molecular dynamics simulation

This paper investigates the impact of taurine as an additive on the structural and functional stability of urate oxidase. First, the effect of the processing parameters for the stabilization of Urate Oxidase (UOX) using taurine was examined using the response surface methodology (RSM) and the central composite design (CCD) model. Also, the study examines thermodynamic and kinetic parameters as well as structural changes of urate oxidase with and without taurine. Fluorescence intensity changes indicated static quenching during taurine binding. The obtained result indicates that taurine has the ability to preserve the native structural conformation of UOX. Furthermore, molecular dynamics simulation is conducted in order to get insights into the alterations in the structure of urate oxidase in the absence and presence of taurine under optimal conditions. The molecular dynamics simulation section investigated the formation of hydrogen bonds (H-bonds) between different components as well as analysis of root mean square deviation (RMSD), root mean square fluctuations (RMSF) and secondary structure. Lower Cα-RMSD and RMSF values indicate greater stabilization of the taurine-treated UOX structure compared to the free enzyme. The results of molecular docking indicate that the binding of taurine to the UOX enzyme through hydrophobic interactions is associated with a negative value for the Gibbs free energy.

Comprehensive evaluation of recombinant lactate dehydrogenase production from inclusion bodies

A broad application spectrum ranging from clinical diagnostics to biosensors in a variety of sectors, makes the enzyme Lactate dehydrogenase (LDH) highly interesting for recombinant protein production. Expression of recombinant LDH is currently mainly carried out in uncontrolled shake-flask cultivations leading to protein that is mostly produced in its soluble form, however in rather low yields. Inclusion body (IB) processes have gathered a lot of attention due to several benefits like increased space-time yields and high purity of the target product. Thus, to investigate the suitability of this processing strategy for ldhL1 production, a fed-batch fermentation steering the production of IBs rather than soluble product formation was developed. It was shown that the space-time-yield of the fermentation could be increased almost 3-fold by increasing qs to 0.25 g g-1 h-1 which corresponds to 21% of qs,max, and keeping the temperature at 37°C after induction. Solubilization and refolding unit operations were developed to regain full bioactivity of the ldhL1. The systematic approach in screening for solubilization and refolding conditions revealed buffer compositions and processing strategies that ultimately resulted in 50% product recovery in the refolding step, revealing major optimization potential in the downstream processing chain. The recovered ldhL1 showed an optimal activity at pH 5.5 and 30∘C with a high catalytic activity and KM values of 0.46 mM and 0.18 mM for pyruvate and NADH, respectively. These features, show that the here produced LDH is a valuable source for various commercial applications, especially considering low pH-environments.

Electrochemical enzyme-based blood uric acid biosensor: new insight into the enzyme immobilization on the surface of electrode via poly-histidine tag

In a new approach, we considered the special affinity between Ni and poly-histidine tags of recombinant urate oxidase to utilize Ni-MOF for immobilizing the enzyme. In this study, a carbon paste electrode (CPE) was modified by histidine-tailed urate oxidase (H-UOX) and nickel-metal-organic framework (Ni-MOF) to construct H-UOX/Ni-MOF/CPE, which is a rapid, sensitive, and simple electrochemical biosensor for UA detection. The use of carboxy-terminal histidine-tailed urate oxidase in the construction of the electrode allows the urate oxidase enzyme to be positioned correctly in the electrode. This, in turn, enhances the efficiency of the biosensor. Characterization was carried out by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and field emission scanning electron microscopy (FE-SEM). At optimum conditions, the biosensor provided a short response time, linear response within 0.3-10 µM and 10-140 µM for UA with a detection limit of 0.084 µM, repeatability of 3.06%, and reproducibility of 4.9%. Furthermore, the biosensor revealed acceptable stability and selectivity of UA detection in the presence of the commonly coexisted ascorbic acid, dopamine, L-cysteine, urea, and glucose. The detection potential was at 0.4 V vs. Ag/AgCl.

Application of magnetic field (MF) as an effective method to improve the activity of immobilized Candida antarctica lipase B (CALB)

The process of immobilized enzyme and the change mechanism of enzyme in magnetic field.

ATP Can Efficiently Stabilize Protein through a Unique Mechanism

Recent experiments suggested that ATP can effectively stabilize protein structure and inhibit protein aggregation when its concentration is less than 10 mM, which is significantly lower than cosolvent concentrations required in conventional mechanisms. The ultrahigh efficiency of ATP suggests a unique mechanism that is fundamentally different from previous models of cosolvents. In this work, we used molecular dynamics simulation and experiments to study the interactions of ATPs with three proteins: lysozyme, ubiquitin, and malate dehydrogenase. ATP tends to bind to the surface regions with high flexibility and high degree of hydration. These regions are also vulnerable to thermal perturbations. The bound ATPs further assemble into ATP clusters mediated by Mg2+ and Na+ ions. More interestingly, in Mg2+-free ATP solution, Na+ at higher concentration (150 mM under physiological conditions) can similarly mediate the formation of the ATP cluster on protein. The ATP cluster can effectively reduce the fluctuations of the vulnerable region and thus stabilize the protein against thermal perturbations. Both ATP binding and the considerable improvement of thermal stability of ATP-bound protein were verified by experiments.