Immobilization of pectinase on the glass bead using polyaldehyde kefiran as a new safe cross-linker and its effect on the activity and kinetic parameters

Synergistic hydrolysis of lignocellulosic biomass using co-immobilization of tri-enzymes on chitosan-magnetite nanoparticle beads

This paper presents the co-immobilization of three enzymes-laccase, cellulase, and xylanase-on chitosan-magnetite nanoparticle beads, with process parameters optimized using response surface methodology on glutaraldehyde-activated chitosan-magnetite beads. The optimization achieved an impressive immobilization yield of 95.25%. Following immobilization on chitosan-magnetite beads (CMBs), the kinetic properties (Km and Vmax), as well as the optimal pH and temperature, were significantly enhanced. The immobilized LCX demonstrated excellent reusability, maintaining 51% of its initial activity after five consecutive cycles, and could be easily recovered using an external magnet. Maximum digestibility of cellulose (% Dc), hemicellulose (% DH), and lignin (% DL) was observed when 10 g of pretreated wheat bran was treated with 20 LCX-loaded CMBs at 40 °C for 60 minutes. The digestibility values for cellulose, hemicellulose, and lignin were 42.10 ± 1.85%, 52.30 ± 2.05%, and 18.12 ± 0.96%, respectively, using immobilized LCX-CMBs-1.0 to 1.5 times higher than those obtained with free enzymes. Additionally, the yield of reducing sugars was 62.17% for immobilized LCX compared to 46.06% for free LCX. The immobilization on CMBs offers an easily removable and cost-effective solution for various industrial applications.

A highly sensitive, accurate, and stable method for measuring pectin depolymerase activity

Pectin depolymerase is widely utilized in various industrial sectors. However, the traditional methods for determining its enzymatic activity have limitations, such as cumbersome operations and a significant impact of enzyme solution dilution ratios on activity. The 3-methyl-2-benzothiazolinone hydrazone (MBTH) method can be employed to address these issues, but pectin precipitation and strong background commonly arise in this method. We have successfully overcome these challenges by employing a low-temperature and high-alkaline environment, and further optimized the reagent compositions and detection wavelength to improve the method. Consequently, enzyme hydrolysis follows a zero-order reaction within 60 min, which is helpful for the endpoint measurement of pectinase activity. The developed calibration curve for pectinase concentration and hydrolysis rate demonstrates linearity (R2 = 0.9945) within the range of 2.5-15.8 mU/mL of pectinase. This method exhibits high sensitivity, accuracy, and stability, making it suitable for routine determination of pectin depolymerase activity in research and applications.

Pros and Cons in Various Immobilization Techniques and Carriers for Enzymes

In recent years, enzyme immobilization technology has been developed, and studies on immobilized enzyme materials have become very prominent. With the immobilization technique, enzymes and compatible carrier materials are combined or enzyme crystals/aggregates are used in a carrier-free fashion, by physical, chemical, or biochemical methods. As a kind of biocatalyst, immobilized enzymes can catalyze certain chemical reactions with high selectivity and high efficiency under relatively mild reaction conditions and eliminate pollution to the environment. Considering the current status and applications of immobilized enzyme technology and materials emerging in the last 5 years, this mini-review introduces the advantages and disadvantages of various enzyme immobilization techniques with carriers as well as the pros and cons of different materials for immobilization. The future prospects of immobilization technology and carrier materials are outlined, aiming to provide a reference for further research and applications of sustainable technology.

Regulation of cell differentiation to promote pullulan synthesis in Aureobasidium pullulans NG

Pullulan is a polymer produced by Aureobasidium spp. The yield of pullulan production can be impacted by the cellular differentiation of Aureobasidium spp., which changes with alterations in the growth environment. To improve pullulan yield, identifying key factors that regulate cellular differentiation is crucial. In this study, the main form of pullulan synthesis in Aureobasidium pullulans NG was through swollen cells (SC). The results showed that citric acid (CA) can regulate the cellular differentiation of Aureobasidium pullulans NG by accumulating higher levels of CA in the cells to maintain growth in SC form and increase pullulan production. The addition of 1.0% CA to Aureobasidium pullulans NG for 96 h resulted in a significant increase in pullulan production, producing 18.32 g/l compared to the control group which produced 10.23 g/l. Our findings suggest that controlling cellular differentiation using CA is a promising approach for enhancing pullulan production in Aureobasidium pullulans. KEY POINTS: • The regulation of cell differentiation in Aureobasidium pullulans NG is demonstrated to be influenced by citric acid. • Intracellular citric acid levels in Aureobasidium pullulans NG have been shown to support the growth of swollen cells. • Citric acid has been found to increase pullulan production in Aureobasidium pullulans NG.

Directional immobilization of D-allulose 3-epimerase using SpyTag/SpyCatcher strategy as a robust biocatalyst for synthesizing D-allulose

D-Allulose, as low-calorie rare sugar, possessed several notable biological activities and was biosynthesized by D-allulose 3-epimerase (DAEase). Here, CcDAE from Clostridium cellulolyticum was successfully immobilization via covalent attachment (RI-CcDAE), and Resin-SpyCatcher/SpyTag-CcDAE modular (DI-CcDAE). Both immobilized CcDAEs exhibited higher thermal and pH stabilities than the free form, and they maintained 80.0 % of relative activity after 7 consecutive cycles and 25 days of storage. Predominantly, DI-CcDAE represented superior catalytic efficiency with a 2.4-fold increase of k_cat/K_m, compared with RI-CcDAE (0.75 s^-1 mM^-1 vs 0.31 s^-1 mM^-1). The RI-CcDAE and DI-CcDAE were then applied in mixed fruit Jiaosu to convert D-fructose into D-allulose, which exhibited the productivity of D-allulose 1.08 g/Lh^-1 and 1.57 g/Lh^-1, respectively. This research provided a promising directional immobilization strategy for DAEase, and robust biocatalyst for production of functional foodstuff containing D-allulose.

Covalent Immobilization of Chondrostereum purpureum Endopolygalacturonase on Ferromagnetic Nanoparticles: Catalytic Properties and Biotechnological Application

Pectinases are widely used in a variety of industrial processes. However, their application is limited by low catalytic processivity, reduced stability, high cost, and poor re-use compatibility. These drawbacks may be overcome by enzyme immobilization with ferromagnetic nanoparticles, which are easily recovered by a magnetic field. In this work, an endopolygalacturonase from Chondrostereum purpureum (EndoPGCp) expressed in Pichia pastoris was immobilized on glutaraldehyde-activated chitosan ferromagnetic nanoparticles (EndoPGCp-MNP) and used to supplement a commercial enzyme cocktail. No significant differences in biochemical and kinetic properties were observed between EndoPGCp-MNP and EndoPGCp, although the EndoPGCp-MNP showed slightly increased thermostability. Cocktail supplementation with EndoPGCp-MNP increased reducing sugar release from orange wastes by 1.8-fold and showed a synergistic effect as compared to the free enzyme. Furthermore, EndoPGCp-MNP retained 65% of the initial activity after 7 cycles of re-use. These properties suggest that EndoPGCp-MNP may find applications in the processing of pectin-rich agroindustrial residues.

Continuous Clarification of Barberry Juice with Pectinase Immobilised by Oxidized Polysaccharides

Research background

Barberry juice is a rich source of bioactive compounds and shows different health properties such as antioxidant and anticancer activities. Clarification, as the removal process of suspended material, is an important step in the production of fruit juice due to its significant effect on the appearance, flavour and commercialisation of juice. Pectinase is the most important enzyme applied in juice clarification that breaks down the pectin polymer structure and reduces the undesirable turbidity. Pectinase immobilisation is a way to overcome free enzyme drawbacks such as instability, high cost, the difficulty of recovery and recyclability. Also, continuous clarification process which is highly preferred in fruit juice industry is not possible without enzyme immobilisation.

Experimental approach

Pectinase enzymes were immobilised on the functionalised glass beads (glass bead with (3-aminopropyl)triethoxysilane) by glutaraldehyde, polyaldehyde derivatives of pullulan and kefiran and the barberry juice was clarified in the batch and continuous processes in a packed bed reactor (PBR). Also, the effect of clarification on the physicochemical and antioxidant properties of the barberry juice samples was evaluated.

Results and conclusions

The optimum conditions for clarification in the PBR were: flow rate 0.5 mL/min, temperature 50 °C and treatment time 63 min. Clarification led to a decrease in turbidity, pH, total soluble solid content, viscosity, total phenolic content and antioxidant activity of the juice samples. Also, this process increased the clarity, acidity, reducing sugar concentration and the lightness parameter of the barberry juice. The greatest effect of clarification on the studied properties of barberry juice was related to the pectinase immobilised by the polyaldehyde of kefiran in the continuous process and both new cross-linkers (polyaldehyde derivatives of pullulan and kefiran) immobilised the enzyme better than the common cross-linker (glutaraldehyde).

Novelty and scientific contribution

For the first time, barberry juice was clarified with pectinase immobilised by polyaldehyde derivatives of pullulan and kefiran and the obtained results showed that the pectinase immobilisation by these new cross-linkers was much more efficient than by the glutaraldehyde as a common cross-linker. These findings can be of use for an industrialised production of fruit juices.

Octenyl succinylation of kefiran: Preparation, characterization and functional properties

In this study, kefiran was esterified with octenyl succinic anhydride (OSA). The esterification reaction variables including pH (8.5), kefiran concentration (5% (w/w)), OSA concentration (12% (w/w)), temperature (~38 °C) and reaction time (~80 min) were found as optimum points to achieve the maximum degree of substitution (DS) (0.041 ± 0.002). Kefiran-OSA samples with DS of 0.021 (FDA suggested DS) and 0.041 (maximum DS) were prepared and compared with unmodified kefiran in all experiments. FTIR and ¹H NMR spectroscopies proved the grafting of OSA on kefiran structure. XRD analysis revealed that with increase in DS, the physical state of kefiran to be more amorphous. In addition, the esterification modification led to a decrease in the degradation temperature and an increase in the apparent viscosity based on the obtained data from thermal analysis and viscosity measurement. The results of the foaming and emulsifying properties confirmed the improvement in surface properties of the modified kefiran. The frequency sweep test illustrated that with an increase in DS, the viscoelastic behavior of the kefiran cryogels to be more viscous. It can finally be stated that the modification with OSA was a high potential strategy to extend the industrial applications of the kefiran.