Immunolocalization of β-glucosidase immobilized within polysulphone capillary membrane and evaluation of its activity in situ

Harnessing Mucor spp. for Xylanase Production: Statistical Optimization in Submerged Fermentation Using Agro-Industrial Wastes

Xylan is the primary hemicellulosic polymer found in lignocellulosic agricultural wastes and can be degraded by xylanase. In the current research, Mucor circinelloides and M. hiemalis were tested for their ability to produce xylanase from tangerine peel by submerged fermentation. Experiments on five variables were designed with Box–Behnken design and response surface methodology. Analysis of variance was exercised, the xylanase output was demonstrated with a mathematical equation as a function of the five factors, and the quixotic states for xylanase biosynthesis was secured. In addition, xylanase was partially purified, characterized, and immobilized on calcium alginate beads. The optimum parameters for xylanase production by M. circinelloides and M. hiemalis were consisted of incubation temperature (30 and 20°C), pH value (9 and 7) incubation period (9 and 9 days), inoculum size (3 and 3 mL), and substrate concentration (3 and 3 g/100 mL), respectively. M. circinelloides and M. hiemalis demonstrated the highest xylanase activities after RSM optimization, with 42.23 and 35.88 U/mL, respectively. The influence of single, interchange, and quadratic factors on xylanase output was investigated using nonlinear regression equations with significant R² and p values. The partial purification of M. circinelloides and M. hiemalis xylanase yielded 1.69- and 1.97-fold purification, and 30.74 and 31.34% recovery with 292.08 and 240.15 U/mg specific activity, respectively. Partially purified xylanase from M. circinelloides and M. hiemalis demonstrated the highest activity at neutral pH and 60 and 50°C, respectively. The immobilized M. circinelloides and M. hiemalis xylanase retained 84.02 and 79.43% activity, respectively. The production of xylanase from M. circinelloides and M. hiemalis utilizing RSM is deemed profitable for the decomposition of the agro-industrial wastes.

Immobilization of Glycoside Hydrolase Families GH1, GH13, and GH70: State of the Art and Perspectives

Glycoside hydrolases (GH) are enzymes capable to hydrolyze the glycosidic bond between two carbohydrates or even between a carbohydrate and a non-carbohydrate moiety. Because of the increasing interest for industrial applications of these enzymes, the immobilization of GH has become an important development in order to improve its activity, stability, as well as the possibility of its reuse in batch reactions and in continuous processes. In this review, we focus on the broad aspects of immobilization of enzymes from the specific GH families. A brief introduction on methods of enzyme immobilization is presented, discussing some advantages and drawbacks of this technology. We then review the state of the art of enzyme immobilization of families GH1, GH13, and GH70, with special attention on the enzymes β-glucosidase, α-amylase, cyclodextrin glycosyltransferase, and dextransucrase. In each case, the immobilization protocols are evaluated considering their positive and negative aspects. Finally, the perspectives on new immobilization methods are briefly presented.

Cascade catalysis in membranes with enzyme immobilization for multi-enzymatic conversion of CO2 to methanol

Facile co-immobilization of enzymes is highly desirable for bioconversion methods involving multi-enzymatic cascade reactions. Here we show for the first time that three enzymes can be immobilized in flat-sheet polymeric membranes simultaneously or separately by simple pressure-driven filtration (i.e. by directing membrane fouling formation), without any addition of organic solvent. Such co-immobilization and sequential immobilization systems were examined for the production of methanol from CO2 with formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH) and alcohol dehydrogenase (ADH). Enzyme activity was fully retained by this non-covalent immobilization strategy. The two immobilization systems had similar catalytic efficiencies because the second reaction (formic acid→formaldehyde) catalyzed by FaldDH was found to be the cascade bottleneck (a threshold substrate concentration was required). Moreover, the trade-off between the mitigation of product inhibition and low substrate concentration for the adjacent enzymes probably made the co-immobilization meaningless. Thus, sequential immobilization could be used for multi-enzymatic cascade reactions, as it allowed the operational conditions for each single step to be optimized, not only during the enzyme immobilization but also during the reaction process, and the pressure-driven mass transfer (flow-through mode) could overcome the diffusion resistance between enzymes. This study not only offers a green and facile immobilization method for multi-enzymatic cascade systems, but also reveals the reaction bottleneck and provides possible solutions for the bioconversion of CO2 to methanol.

Fouling-induced enzyme immobilization for membrane reactors

A simple enzyme immobilization method accomplished by promoting membrane fouling formation is proposed. The immobilization method is based on adsorption and entrapment of the enzymes in/on the membrane. To evaluate the concept, two membrane orientations, skin layer facing feed (normal mode) and support layer facing feed (reverse mode), were used to immobilize alcohol dehydrogenase (ADH, EC 1.1.1.1) and glutamate dehydrogenase (GDH, EC 1.4.1.3), respectively. The nature of the fouling in each mode was determined by filtration fouling models. The permeate flux was larger in the normal mode, but the reverse mode allowed for higher enzyme loading and stability, and irreversible fouling (i.e. pore blocking) developed more readily in the support structure than in the skin layer. Compared with an enzymatic membrane reactor (EMR) with free enzymes, the novel EMR with enzymes immobilized in membrane support improved the enzyme reusability (especially for ADH), and reduced the product inhibition (especially for GDH).