Immobilization of His-tagged recombinant xylanase from Penicillium occitanis on nickel-chelate Eupergit C for increasing digestibility of poultry feed

Xylanase covalent binding onto amidated pectin beads: Optimization, thermal, operational and storage stability studies and application

Amidated pectin-polyethylene imine-glutaraldehyde (AP-PEI-GA) immobilizer was prepared. The ideal protocol that should be adopted during the immobilizer preparation was investigated via Box-Behnken design (BBD), and it comprised processing the AP beads with 3.4 % (w/w) PEI solution of pH 9.65 followed by 5.96 % (v/v) GA solution. The obtained AP-PEI-GA immobilizer was efficient, and it acquired 3.03 U.g^-1 of immobilized xylanase (im-xylanase) activity. The computed K_m and V_max values for AP-PEI-GA im-xylanase were 16.67 mg.ml^-1 and 20 g.ml^-1.min^-1, respectively. Through covalent coupling to AP-PEI-GA, Aspergillus niger xylanase thermodynamic properties T_1/2 and D-values were increased by 2.05, 3.08, and 1.35 at 40, 50, and 60 °C, respectively. ΔH_d and ΔG_d for AP-PEI-GA im-xylanase at 40, 50, and 60 °C were higher than those for free form emphasizing more resistance to thermal denaturation. Im-xylanase showed 100 % activity for 20 successive cycles and hydrolyzed different agro-industrial wastes into reducing sugar and xylooligosaccharides (XOS) with more efficiency on pea peel (PP). AP-PEI-GA im-xylanase, PP weight, and hydrolysis time that should be adopted to obtain the highest reducing sugar and XOS yield were optimized through central composite design (CCD). Extracted XOS showed prebiotic and anti-oxidant activities.

Mechano-chemical and biological energetics of immobilized enzymes onto functionalized polymers and their applications

Enzymes of commercial importance, such as lipase, amylase, laccase, phytase, carbonic anhydrase, pectinase, maltase, glucose oxidase etc., show multifunctional features and have been extensively used in several fields including fine chemicals, environmental, pharmaceutical, cosmetics, energy, food industry, agriculture and nutraceutical etc. The deployment of biocatalyst in harsh industrial conditions has some limitations, such as poor stability. These drawbacks can be overcome by immobilizing the enzyme in order to boost the operational stability, catalytic activity along with facilitating the reuse of biocatalyst. Nowadays, functionalized polymers and composites have gained increasing attention as an innovative material for immobilizing the industrially important enzyme. The different types of polymeric materials and composites are pectin, agarose, cellulose, nanofibers, gelatin, and chitosan. The functionalization of these materials enhances the loading capacity of the enzyme by providing more functional groups to the polymeric material and hence enhancing the enzyme immobilization efficiency. However, appropriate coordination among the functionalized polymeric materials and enzymes of interest plays an important role in producing emerging biocatalysts with improved properties. The optimal coordination at a biological, physical, and chemical level is requisite to develop an industrial biocatalyst. Bio-catalysis has become vital aspect in pharmaceutical and chemical industries for synthesis of value-added chemicals. The present review describes the current advances in enzyme immobilization on functionalized polymers and composites. Furthermore, the applications of immobilized enzymes in various sectors including bioremediation, biosensor and biodiesel are also discussed.

High specific immobilization of His-tagged recombinant Microbacterium esterase by Ni-NTA magnetic chitosan microspheres for efficient synthesis of key chiral intermediate of d-biotin

The novel Ni-NTA-functionalized magnetic chitosan microspheres (MCS-NTA-Ni) were prepared via amino functionalization of MCS with epichlorohydrin and ethylenediamine, followed by the introduction of the aldehyde groups and NTA in turn, and nickel (II) ions were chelated in the end. MCS-NTA-Ni contained numerous long-armed NTA-Ni surface groups, ensuring high enzyme loading and providing more space and flexibility to attach enzymes and maintain their activity. This microsphere can have highly selective adsorption of his-tagged recombinant protein. The his-tagged recombinant Microbacterium esterase of E. coli BL21 (DE3)/pET21a-EstSIT01 was first immobilized on MCS-NTA-Ni by affinity fixation, giving high immobilization yield (90.1%) and enzyme loading (120 mg/g). Compared with free esterase, the immobilized esterase was found to exhibit higher pH stability and thermal stability. In addition, the immobilized esterase had excellent reusability for the synthesis of key chiral intermediate of d-biotin and the substrate conversion could still keep 100% after 8 cycles continuously.

Biochemical characterization and enhanced production of endoxylanase from thermophilic mould Myceliophthora thermophila

Endoxylanase production from M. thermophila BJTLRMDU3 using rice straw was enhanced to 2.53-fold after optimization in solid state fermentation (SSF). Endoxylanase was purified to homogeneity employing ammonium sulfate precipitation followed by gel filtration chromatography and had a molecular mass of ~ 25 kDa estimated by SDS-PAGE. Optimal endoxylanase activity was recorded at pH 5.0 and 60 °C. Purified enzyme showed complete tolerance to n-hexane, but activity was slightly inhibited by other organic solvents. Among surfactants, Tweens (20, 60, and 80) and Triton X 100 slightly enhanced the enzyme activity. The V_max and K_m values for purified endoxylanase were 6.29 µmol/min/mg protein and 5.4 mg/ml, respectively. Endoxylanase released 79.08 and 42.95% higher reducing sugars and soluble proteins, respectively, which control after 48 h at 60 °C from poultry feed. Synergistic effect of endoxylanase (100 U/g) and phytase (15 U/g) on poultry feed released higher amount of reducing sugars (58.58 mg/feed), soluble proteins (42.48 mg/g feed), and inorganic phosphate (28.34 mg/feed) in contrast to control having 23.55, 16.98, and 10.46 mg/feed of reducing sugars, soluble proteins, and inorganic phosphate, respectively, at 60 °C supplemented with endoxylanase only.

Cross-Linking with Polyethylenimine Confers Better Functional Characteristics to an Immobilized β-glucosidase from Exiguobacterium antarcticum B7

β-glucosidases are ubiquitous, well-characterized and biologically important enzymes with considerable uses in industrial sectors. Here, a tetrameric β-glucosidase from Exiguobacterium antarcticum B7 (EaBglA) was immobilized on different activated agarose supports followed by post-immobilization with poly-functional macromolecules. The best result was obtained by the immobilization of EaBglA on metal glutaraldehyde-activated agarose support following cross-linking with polyethylenimine. Interestingly, the immobilized EaBglA was 46-fold more stable than its free form and showed optimum pH in the acidic region, with high catalytic activity in the pH range from 3 to 9, while the free EaBglA showed catalytic activity in a narrow pH range (>80% at pH 6.0–8.0) and optimum pH at 7.0. EaBglA had the optimum temperature changed from 30 °C to 50 °C with the immobilization step. The immobilized EaBglA showed an expressive adaptation to pH and it was tolerant to ethanol and glucose, indicating suitable properties involving the saccharification process. Even after 9 cycles of reuse, the immobilized β-glucosidase retained about 100% of its initial activity, demonstrating great operational stability. Hence, the current study describes an efficient strategy to increase the functional characteristics of a tetrameric β-glucosidase for future use in the bioethanol production.

Production of xylooligosaccharides from hardwood xylan by using immobilized endoxylanase of Clostridium strain BOH3

Endoxylanase ofClostridiumsp. BOH3 was immobilized in calcium alginate/silica gel matrix with a 100% yield. This immobilized xylanase can be reused 7 times to produce prebiotic xylooligosaccharides from hardwood xylan with 62% of activity recovery.

Molecular cloning, overexpression, purification and crystallographic analysis of a GH43 β-xylosidase from Bacillus licheniformis

β-Xylosidases (EC 3.2.1.37) catalyze the hydrolysis of short xylooligosaccharides into xylose, which is an essential step in the complete depolymerization of xylan, the major hemicellulosic polysaccharide of plant cell walls, and has great biotechnological relevance for the production of lignocellulose-based biofuels and the paper industry. In this study, a GH43 β-xylosidase identified from the bacterium Bacillus licheniformis (BlXylA) was cloned into the the pET-28a bacterial expression vector, recombinantly overexpressed in Escherichia coli BL21(DE3) cells and purified to homogeneity by metal-affinity and size-exclusion chromatography. The protein was crystallized in the presence of the organic solvent 2-methyl-2,4-pentanediol and a single crystal diffracted to 2.49 Å resolution. The X-ray diffraction data were indexed in the monoclinic space group C2, with unit-cell parameters a = 152.82, b = 41.9, c = 71.79 Å, β = 91.7°. Structural characterization of this enzyme will contribute to a better understanding of the structural requirements for xylooligosaccharide specificity within the GH43 family.