Kinetic and thermodynamic parameters of immobilized glucoamylase on different mesoporous silica for starch hydrolysis: A comparative study

The application of conventional or magnetic materials to support immobilization of amylolytic enzymes for batch and continuous operation of starch hydrolysis processes

In the production of ethanol, starches are converted into reducing sugars by liquefaction and saccharification processes, which mainly use soluble amylases. These processes are considered wasteful operations as operations to recover the enzymes are not practical economically so immobilizations of amylases to perform both processes appear to be a promising way to obtain more stable and reusable enzymes, to lower costs of enzymatic conversions, and to reduce enzymes degradation/contamination. Although many reviews on enzyme immobilizations are found, they only discuss immobilizations of α-amylase immobilizations on nanoparticles, but other amylases and support types are not well informed or poorly stated. As the knowledge of the developed supports for most amylase immobilizations being used in starch hydrolysis is important, a review describing about their preparations, characteristics, and applications is herewith presented. Based on the results, two major groups were discovered in the last 20 years, which include conventional and magnetic-based supports. Furthermore, several strategies for preparation and immobilization processes, which are more advanced than the previous generation, were also revealed. Although most of the starch hydrolysis processes were conducted in batches, opportunities to develop continuous reactors are offered. However, the continuous operations are difficult to be employed by magnetic-based amylases.

Expanding the Applicability of an Innovative Laccase TTI in Intelligent Packaging by Adding an Enzyme Inhibitor to Change Its Coloration Kinetics

Enzymatic time–temperature indicators (TTIs) usually suffer from instability and inefficiency in practical use as food quality indicator during storage. The aim of this study was to address the aforementioned problem by immobilizing laccase on electrospun chitosan fibers to increase the stability and minimize the usage of laccase. The addition of NaN₃, as and enzyme inhibitor, was intended to extend this laccase TTI coloration rate and activation energy (Ea) range, so as to expand the application range of TTIs for evaluating changes in the quality of foods during storage. A two-component time–temperature indicator was prepared by immobilizing laccase on electrospun chitosan fibers as a TTI film, and by using guaiacol solution as a coloration substrate. The color difference of the innovative laccase TTI was discovered to be <3, and visually indistinguishable when OD₅₀₀ reached 3.2; the response reaction time was regarded as the TTI’s coloration endpoint. Enzyme immobilization and the addition of NaN₃ increased coloration Km and reduced coloration Vmax. The coloration Vmax decreased to 64% when 0.1 mM NaN₃ was added to the TTI, which exhibited noncompetitive inhibition and a slower coloration rate. Coloration hysteresis appeared in the TTI with NaN₃, particularly at low temperatures. For TTI coloration, the Ea increased to 29.92–66.39 kJ/mol when 15–25 μg/cm² of laccase was immobilized, and the endpoint increased to 11.0–199.5 h when 0–0.10 mM NaN₃ was added. These modifications expanded the applicability of laccase TTIs in intelligent food packaging.

Thermodynamics, kinetics and optimization of catalytic behavior of polyacrylamide-entrapped carboxymethyl cellulase (CMCase) for prospective industrial use

In the current study, kinetic and thermodynamic parameters of free and polyacrylamide-immobilized CMCase were analyzed. The maximum immobilization yield of 34 ± 1.7% was achieved at 11% acrylamide. The enthalpy of activation (ΔH) of free and immobilized enzyme was found to be 13.61 and 0.29 kJ mol^-1, respectively. Irreversible inactivation energy of free and immobilized CMCase was 96.43 and 99.01 kJ mol^-1, respectively. Similarly, the enthalpy of deactivation (ΔH_d) values for free and immobilized enzyme were found to be in the range of 93.51-93.76 kJ mol^-1 and 96.08-96.33 kJ mol^-1, respectively. Michaelis-Menten constant (K_m) increased from 1.267 ± 0.06 to 1.5891 ± 0.07 mg ml^-1 and the maximum reaction rate (V_max) value decreased (8319.47 ± 416 to 5643.34 ± 282 U ml^-1 min^-1) after immobilization. Due to wide pH and temperature stability profile with sufficient reusing efficiency up to three successive cycles, the immobilized CMCase might be useful for various industrial processes.

Immobilization of polyphenol oxidase on chitosan/organic rectorite composites for phenolic compounds removal

Chitosan/organic rectorite (CTS/OREC) composites were prepared and characterized by Fourier transform infrared spectrometry and X-ray diffraction. Polyphenol oxidase (PPO) was immobilized on CTS/OREC by physical adsorption (APPO) and covalent binding (CPPO). Taguchi method was applied in the optimization of immobilization conditions resulting in the highest enzyme activity of 16.37 × 10³ and 8.92 × 10³U/g for APPO and CPPO, respectively. APPO enzyme activity was higher than that of CPPO, while CPPO showed the higher enzyme loading capacity than that of APPO. The removal percentage of phenolic compound, including phenol (PH), 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP), by immobilized PPO was also explored. The results indicated that APPO was more efficient in phenolic compounds removal than CPPO. APPO contributed to a quick removal in the first hour, and the removal percentage of PH, 4-CP and 2,4-DCP could reach 69.3 ± 4.2%, 89.8 ± 2.5% and 93.8 ± 1.7% within 2 h, respectively. The order of removal percentage of phenolic compounds for both immobilized PPO was 2,4-DCP > 4-CP > PH. After 10 consecutive operations, the removal percentage of 2,4-DCP reached 73.2 ± 2.6% and 60.3 ± 1.5% for APPO and CPPO, respectively. The results introduced a novel support for PPO immobilization, and the immobilized PPO had great potential in wastewater treatment.

Immobilization of enzymes on nanoinorganic support materials: An update

Despite the widespread use in various industries, enzyme's instability and non-reusability limit their applications which can be overcome by immobilization. The nature of the enzyme's support material and method of immobilization affect activity, stability, and kinetics properties of enzymes. Here, we report a comparative study of the effects of inorganic support materials on immobilized enzymes. Accordingly, immobilization of enzymes on nanoinorganic support materials significantly improved thermal and pH stability. Furthermore, immobilizations of enzymes on the materials mainly increased K_m values while decreased the V_max values of enzymes. Immobilized enzymes on nanoinorganic support materials showed the increase in ΔG value, and decrease in both ΔH and ΔS values. In contrast to weak physical adsorption immobilization, covalently-bound and multipoint-attached immobilized enzymes do not release from the support surface to contaminate the product and thus the cost is decreased while the product quality is increased. Nevertheless, nanomaterials can enter the environment and increase health and environmental risks and should be used cautiously. Altogether, it can be predicated that hybrid support materials, directed immobilization methods, site-directed mutagenesis, recombinant fusion protein technology, green nanomaterials and trailor-made supports will be used increasingly to produce more efficient immobilized industrial enzymes in near future.

Advances in Recombinant Lipases: Production, Engineering, Immobilization and Application in the Pharmaceutical Industry

Lipases are one of the most used enzymes in the pharmaceutical industry due to their efficiency in organic syntheses, mainly in the production of enantiopure drugs. From an industrial viewpoint, the selection of an efficient expression system and host for recombinant lipase production is highly important. The most used hosts are Escherichia coli and Komagataella phaffii (previously known as Pichia pastoris) and less often reported Bacillus and Aspergillus strains. The use of efficient expression systems to overproduce homologous or heterologous lipases often require the use of strong promoters and the co-expression of chaperones. Protein engineering techniques, including rational design and directed evolution, are the most reported strategies for improving lipase characteristics. Additionally, lipases can be immobilized in different supports that enable improved properties and enzyme reuse. Here, we review approaches for strain and protein engineering, immobilization and the application of lipases in the pharmaceutical industry.

The effect of arsenic on soil intracellular and potential extracellular β-glucosidase differentiated by chloroform fumigation

Arsenic (As) contamination of soil is a global issue of serious ecological and human health concern. For better use of soil enzymes as biological indicators of As pollution, the response of soil β-glucosidase in different pools of soil (total, intracellular and potential extracellular) to As(V) stress was investigated. Chloroform fumigation method was employed to distinguish the intracellular and potential extracellular β-glucosidase in three soils. The intracellular and potential extracellular β-glucosidase accounted about 79% and 21% of the total β-glucosidase activity in the tested soils. Moreover, it was found that the response of these three enzyme pools to As(V) pollution was different. Under the stress of 400 mg kg^-1 As(V), the β-glucosidase activities decreased by 69%, 79%, and 28% for the total, intracellular and potential extracellular pools, respectively. The calculated median ecological dose (ED₅₀) showed the highest value for potential extracellular β-glucosidase (19.55-27.63 mg kg^-1 for total, 18.49-27.42 mg kg^-1 for intracellular, and 32.27-52.69 mg kg^-1 for potential extracellular β-glucosidase). As(V) exhibited an uncompetitive inhibition for total and intracellular β-glucosidase and non-competitive inhibition for potential extracellular enzyme. The inhibition constant (K_iu) is biggest for potential extracellular β-glucosidase among the three enzyme pools (0.61-0.79 mmol L^-1 for total, 0.34-0.36 mmol L^-1 for intracellular, and 4.01-23.90 mmol L^-1 for potential extracellular β-glucosidase). Thus, compared to potential extracellular β-glucosidase, the total and intracellular β-glucosidases are more suitable for their use as sensitive indicators of As(V) pollution.

Saccharification Kinetics at Optimised Conditions of Tapioca by Glucoamylase Immobilised on Mesostructured Cellular Foam Silica

As insoluble substrates such as tapioca can be used to make chemical compounds, saccharification of tapioca by glucoamylase immobilised on mesostructured cellular foam (MCF) silica using Box-Behnken Design of experiment was conducted to optimize this process so that the experimental results can be used to develop large-scale operations. The experiments gave dextrose equivalent (DE) values of 6.15–69.50% (w/w). Factors of pH and temperature affected the process highly. The suggested quadratic polynomial model is significant and considered acceptable (R2 = 99.78%). Justification of the model confirms its validity and adequacy where the predicted DE shows a good agreement with the experimental results. The kinetic constants (Vmax, KM) produced by the immobilised enzyme differed highly from the values yielded by free glucoamylase indicating reduction of substrate access to enzyme active sites had occurred.

The intensification of amyloglucosidase-based saccharification by ultrasound

The present report studied the role of ultrasound (US) energy in the amyloglucosidase-based starch hydrolysis using two complementary approaches: (i) in the activity of six commercially-available amyloglucosidases (using soluble starch as substrate), and (ii) in the hydrolysis of four pure starches from different botanical sources. This corresponds to the first systematic evaluation of the role of US in starch hydrolysis mediated by amyloglucosidase, being a consequence of our previous report that assessed the effect of US in the activity of alpha-amylase (LWT - Food Science and Technology 84 (2017) 674-685). Regarding amlyloglucosidases, three enzymes obtained from Aspergillus niger (AN1-AN3), and Spirizyme Achieve (SPA), Spirizyme Fuel (SPF) and Spirizyme Ultra (SPU) were submitted to a Box-Behnken experimental design in order to establish the optimum conditions for their maximum activity. In the presence of US, we found both inactivation and activation, ranging from -88% (AN3) to 699% (SPA). The US promoted the enzyme activity when combined with lower temperatures (40-60 °C), with a marked effect in Spirizyme enzymes. Based on the optimum conditions established by the experimental design, we also evaluated the role of US in the glucose yield resulting from the hydrolysis of pure starches (corn, rice, potato, wheat). In this case, US led to higher glucose yields in all conditions tested. The enhancement factors observed ranged from 1.2 (AN1, rice starch) to 65 (SPA, potato starch) times. We compared these findings with previous reports, which highlighted the role of US in intensifying amyloglucosidase-based saccharification in mild conditions, by simultaneously influencing both enzyme and substrate. Hence, US power has to be fine-tuned for each particular enzyme in order to maximize process intensification.

Bienzyme Magnetic Nanobiocatalyst with Fe3+-Tannic Acid Film for One-Pot Starch Hydrolysis

In this study, a novel co-immobilization biocatalyst for one-pot starch hydrolysis was prepared through shielding enzymes on the Fe₃O₄/SiO₂ core-shell nanospheres by a Fe³⁺-tannic acid (TA) film. In brief, α-amylase and glucoamylase were covalently immobilized on amino-modified Fe₃O₄/SiO₂ core-shell nanospheres using glutarldehyde as a linker. Then, a Fe³⁺-TA protective film was formed through the self-assembly of the Fe³⁺ and TA coordination complex (Fe³⁺-TA@Fe₃O₄/SiO₂-enzymes). The film acts a "coating" to prevent the enzyme from denaturation and detachment, thus significantly improving its structural and operational stability. Furthermore, the immobilization efficiency reached 90%, and the maximum activity recovery of α-amylase and glucoamylase was 87 and 85%, respectively. More importantly, the bienzyme magnetic nanobiocatalyst with Fe³⁺-TA film could be simply recovered by a magnet. The Fe³⁺-TA@Fe₃O₄/SiO₂-enzymes kept 55% of the original activity after reuse for 9 cycles, indicating outstanding reusability. However, the bienzyme magnetic nanobiocatalyst without Fe³⁺-TA film maintained 28% of the initial activity.

Regulation of the catalytic behavior of pullulanases chelated onto nickel (II)-modified magnetic nanoparticles

Chelating of pullulanases onto nickel (II)-modified magnetic nanoparticles results in one-step purification and immobilization of pullulanase, and facilitates the commercial application of pullulanase in industrial scale. To improve the catalytic behavior, especially the operational stability, of the nanocatalyst in consecutive batch reactions, we prepared various iminodiacetic acid-modified magnetic nanoparticles differed in surface polarity and spacer length, on which the His6-tagged pullulanases were chelated via nickel ions, and then studied the correlation between the MNPs surface property and the corresponding catalyst behavior. When pullulanases were chelated onto the surface-modified MNPs, the thermostability of all pullulanase derivatives were lower than that of free counterpart, being not relevant to the protein orientation guided by the locality of the His6-tag, but related to the MNPs basal surface polarity and the grafted spacer length. After chelating of pullulanases onto MNPs, there were changes observed in the pH-activity profile and the apparent Michaelis constant toward pullulan. The changing tendencies were mainly dependent on the His6-tagged pullulanase orientation, and the changing extents were tuned by the spacer length. The reusability of pullulanase immobilized by N-terminal His6-tag was higher than that of pullulanase immobilized by C-terminal His6-tag. Moreover, the reusability of the immobilized pullulanase tested increased till grafting polyether amine-400 as spacer-arm, therefore the N-terminal His6-tagged pullulanase chelating MNPs grafted polyether amine-400 gave the best reusability, which retained 60% of initial activity after 18 consecutive cycles with a total reaction time of 9h. Additionally, the correlation analysis of the catalyst behaviors indicated that the reusability was independent from other catalytic properties such as thermostability and substrate affinity. All the results revealed that the catalyst behavior can be mainly controlled by the His6-tagged pullulanase orientation than by the MNPs surface property which can tune the catalyst function.