A catalytic membrane approach as a way to obtain sweet and unsweet lactose-free milk

The growing need in the current market for innovative solutions to obtain lactose-free (L-F) milk is caused by the annual increase in the prevalence of lactose intolerance inside as well as the newborn, children, and adults. Various configurations of enzymes can yield two distinct L-F products: sweet (β-galactosidase) and unsweet (β-galactosidase and glucose oxidase) L-F milk. In addition, the reduction of sweetness through glucose decomposition should be performed in a one-pot mode with catalase to eliminate product inhibition caused by H2O2. Both L-F products enjoy popularity among a rapidly expanding group of consumers. Although enzyme immobilization techniques are well known in industrial processes, new carriers and economic strategies are still being searched. Polymeric carriers, due to the variety of functional groups and non-toxicity, are attractive propositions for individual and co-immobilization of food enzymes. In the presented work, two strategies (with free and immobilized enzymes; β-galactosidase NOLA, glucose oxidase from Aspergillus niger, and catalase from Serratia sp.) for obtaining sweet and unsweet L-F milk under low-temperature conditions were proposed. For free enzymes, achieving the critical assumption, lactose hydrolysis and glucose decomposition occurred after 1 and 4.3 h, respectively. The tested catalytic membranes were created on regenerated cellulose and polyamide. In both cases, the time required for lactose and glucose bioconversion was extended compared to free enzymes. However, these preparations could be reused for up to five (β-galactosidase) and ten cycles (glucose oxidase with catalase).

Deep degradation of atrazine in water using co-immobilized laccase-1-hydroxybenzotriazole-Pd as composite biocatalyst

The efficient and green removal technology of refractory organics such as atrazine in water has been an important topic of research in water treatment. A novel membrane composite biocatalyst Lac-HBT-Pd/BC as prepared for the first time by co-immobilizing laccase, mediator 1-hydroxybenzotriazole (HBT) and metal Pd on functionalized bacterial cellulose (BC) to investigate the removal of atrazine and degradation of its intermediates under mild ambient conditions. It was found that atrazine could be completely degraded in 5 h by the catalysis of Lac-HBT-Pd/BC, and the removal rate of degradation intermediates from atrazine was about 85% after continuous catalysis, which achieved deep degradation of atrazine. The effect of electrochemical activity and radical stability of the membrane composite biocatalysts loaded with Pd was investigated. The possible degradation pathways were proposed by identifying and analyzing the deep degradation products of atrazine. The Lac-HBT-Pd/BC demonstrated deep degradation of atrazine and favorable reusability as well as considerable adaptability to various water qualities. This work provides an important reference for preparing new kinds of biocatalysts to degrade refractory organic pollutants in water.

Enzymatic dual-faced Janus structures based on the hierarchical organic-inorganic hybrid matrix for an effective bioremoval and detoxification of reactive blue-19

A novel, dual-faced, and hierarchical type of Janus hybrid structures (JHSs) was assembled through an in situ growing of lipase@cobalt phosphate sheets on the laccase@copper phosphate sponge-like structures. The chemical and structural information of prepared JHSs was investigated by Scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray diffraction analysis (XRD). The catalytic activity, storage stability, and reusability of JHSs were then investigated. The SEM-EDX analysis clearly confirmed the asymmetric morphology of the fabricated JHSs with two distinct metal distributions. Under optimized synthesis conditions, the prepared JHSs showed 97.8 % and 100 % of laccase and lipase activity, respectively. Compared to the free biocatalysts, the immobilization resulted in ~ a 2-fold increase in laccase and lipase stability at temperatures of >40 °C. The fabricated JHSs maintained 61 % and 90 % of their original laccase and lipase activity upon 12 successive repetition cycles. Up to 80 % of Reactive Blue-19 (RB-19), an anthraquinone-based vinyl sulphone dye, was removed after 5 h treatment with the prepared JHSs (50 % higher than the free forms of laccase and lipase). The dye removal data fitted very well on the pseudo-second-order kinetic model with a rate constant of 0.8 g mg-1 h-1. Following the bioremoval process, bacterial toxicity also decreased by about 70 %. Therefore, the prepared JHSs provide a facile and sustainable approach for the decolorization, biotransformation, and detoxification of RB-19 by integrating enzymatic oxidation and hydrolysis.

Preparation of porous chitin beads from waste crayfish shell and application in the co-immobilization of PLP and its dependent enzyme

In this study, co-immobilization of PLP and its dependent enzyme were investigated using a novel type of porous chitin bead (PCB). Crayfish shell was used to prepare PCB via dissolution of it to form beads, followed by the removal of CaCO3 and protein in-situ. Scanning electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller method showed that the PCB had abundant porous structures with deacetylation degree of 33 % and the specific surface area of 35.87 m2/g. Then, the beads are used to co-immobilize pyridoxal 5-phosphate (PLP) and l-lysine decarboxylase fused with chitin-binding protein (SpLDC-ChBD). Laser scanning confocal microscopy revealed that the beads could co-immobilize PLP and SpLDC-ChBD successfully. In addition, a packed bed was also constructed using the PCB containing co-immobilized SpLDC-ChBD and PLP. The substrate conversion remained at 91.09 % after 48 h with 50 g/L l-lysine, which showed good continuous catalysis ability. This study provides a novel method for co-immobilization of enzyme and PLP, as well as develops a new application of waste crustacean shells.

Glycosylation of polyphenolic compounds: Design of a self-sufficient biocatalyst by co-immobilization of a glycosyltransferase, a sucrose synthase and the cofactor UDP

Glycosyltransferases catalyze the regioselective glycosylation of polyphenolic compounds, increasing their solubility without altering their antioxidant properties. Leloir-type glycosyltransferases require UDP-glucose as a cofactor to glycosylate a hydroxyl of the polyphenol, which is expensive and unstable. To simplify these processes for industrial implementation, the preparation of self-sufficient heterogeneous biocatalysts is needed. In this study, a glycosyltransferase and a sucrose synthase (as an UDP-regenerating enzyme) were co-immobilized onto porous agarose-based supports coated with polycationic polymers: polyethylenimine and polyallylamine. In addition, the UDP cofactor was strongly ionically adsorbed and co-immobilized with the enzymes, eliminating the need to add it separately. Thus, the optimal self-sufficient heterogeneous biocatalyst was able to catalyze the glycosylation of three polyphenolic compounds (piceid, phloretin and quercetin) with in situ regeneration of the UDP-glucose, allowing multiple consecutive reaction cycles without the addition of exogenous cofactor. A TTN value of 50 (theoretical maximum) was obtained in the reaction of piceid glycosylation, after 5 reaction cycles, using the self-sufficient biocatalyst based on an improved sucrose synthase variant. This result was 5-fold higher than the obtained using soluble cofactor and the co-immobilized enzymes, and much higher than those reported in the literature for similar processes.

Co-immobilization of β-xylosidase and endoxylanase on zirconium based metal-organic frameworks for improving xylosidase activity at high temperature and in acetone

Improving the activity of β-xylosidase at high temperature and organic solvents is important for the conversion of xylan, phytochemicals and some hydroxyl-containing substances to produce xylose and bioactive substances. In this study, a β-xylosidase R333H and an endoxylanase were simultaneously co-immobilized on the metal-organic framework UiO-66-NH₂. Compared with the single R333H immobilization system, the co-immobilization enhanced the activity of R333H at high temperature and high concentration of acetone, and the relative activities at 95°C and 50% acetone solution were > 95%. The K_m value of co-immobilized R333H towards p-Nitrophenyl-β-D-xylopyranoside (pNPX) shifted from 2.04 to 0.94 mM, which indicated the enhanced affinity towards pNPX. After 5 cycles, the relative activities of the co-immobilized enzymes towards pNPX and corncob xylan were 52% and 70% respectively, and the accumulated amount of reducing sugars obtained by co-immobilized enzymes degrading corncob xylan in 30% (v/v) acetone solution was 1.7 times than that with no acetone.

A Bifunctional Polymeric Coating for the Co-Immobilization of Proteins and Peptides on Microarray Substrates

The analytical performance of the microarray technique in screening the affinity and reactivity of molecules toward a specific target is highly affected by the coupling chemistry adopted to bind probes to the surface. However, the surface functionality limits the biomolecules that can be attached to the surface to a single type of molecule, thus forcing the execution of separate analyses to compare the performance of different species in recognizing their targets. Here, we introduce a new N,N-dimethylacrylamide-based polymeric coating, bearing simultaneously different functionalities (N-acryloyloxysuccinimide and azide groups) to allow an easy and straightforward method to co-immobilize proteins and oriented peptides on the same substrate. The bifunctional copolymer has been obtained by partial post-polymerization modification of the functional groups of a common precursor. This strategy represents a convenient method to reduce the number of analyses, therefore possible systematic or random errors, besides offering a drastic shortage in time, reagents, and costs.

Efficient production of inulo-oligosaccharides from inulin by exo- and endo-inulinase co-immobilized onto a self-assembling protein scaffold

Inulin can be hydrolyzed by inulinases to yield inulo-oligosaccharides (IOSs), which have great application potential in the food and nutraceutical industries. However, conventional enzymatic production of IOSs is limited by long hydrolysis times and poor thermo-stability of inulinases. Here, the self-assembling protein scaffold EutM was engineered to co-immobilize exo-inulinase (EXINU) and endo-inulinase (ENINU) for synergistic hydrolysis of inulin to produce IOSs with 3 to 5 monosaccharide units (DP3-5 IOSs). The immobilization of EXINU/ENINU onto the EutM scaffold resulted in an increase of catalytic efficiency, a 65% increase of the V_max of ENINU, as well as an increase of thermo-stability, with 4.26-fold higher residual activity of EXINU after 22 h-incubation at 50 °C. After optimization, two efficient production protocols were obtained, in which the yield and productivity of DP3-5 IOSs reached 80.38% and 70.86 g·(L·h)^-1, respectively, which were at a high level in similar studies. Overall, this study provides an attractive self-assembling protein platform for the co-immobilization of inulinases, as well as optimized bioprocesses with great promise for the industrial production of DP3-5 IOSs.

Homologous amino acids promoted co-immobilization of laccase and mediator onto geopolymer microspheres for enhancing degradation of dyes in water

A new strategy for co-immobilization of laccase (Lac) and mediator 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) on geopolymer microspheres (GM) was reported in this work, which was promoted by pre-embedded homologous amino acids, i.e., histidine (His) and cysteine (Cys). The GM-H₂C₁ produced with a His/Cys ratio of 2:1 was highly efficient in co-immobilizing Lac and ABTS. The as-prepared composite biocatalyst (Lac-ABTS@GM-H₂C₁) exhibited the highest degradation rate (94.78%) to the model pollutant (Congo Red, CR), which was superior to free Lac-ABTS (79.23%) and Lac@GM-H₂C₁ (53.82%). The enhanced degradation efficiency of CR by the Lac-ABTS@GM-H₂C₁ was due to the promoted electron transfer and shortened mass transfer distance. Moreover, Lac-ABTS@GM-H₂C₁ demonstrated good pH resistance, competitive storage stability, and good reusability during ten cycles of CR degradation.

Efficient removal of a low concentration of Pb(II), Fe(III) and Cu(II) from simulated drinking water by co-immobilization between low-dosages of metal-resistant/adapted fungus Penicillium janthinillum and graphene oxide and activated carbon

Drinking water safety cannot be overemphasized. Filamentous fungi have many excellent features for metal removal. Both graphene oxide (GO) and activated carbon (AC) are conventional metal adsorbents, but they are not suitable for large-scale use due to high cost. In this study, a low dosage of conidia (2.0 × 10⁴ conidia/mL) of metal-resistant/adapted filamentous fungus Penicillium janthinillum strain GXCR were co-immobilized with a low dosage of 0.5 mg/L GO or 0.5 mg/L AC by embedding in 2% polyvinyl alcohol (PVA)-3% sodium alginate (SA), generating six types of microbead adsorbents (MBAs) to remove metals from a low concentration of either single metal (100 mg/L) or mixed metals (100 mg/L each) of Pb (II), Fe (III) and Cu (II) in drinking water. Fungus GXCR-containing MBAs had higher specific surface areas (SSAs), better mesoporous structures, and a higher removal rate (85-98.99%) of single or mixed metals. Singl-metal adsorptions of MBAs were almost unaffected by temperature changes. MBAs showed a stable removal rate of 87-94% during four cycles of adsorption-desorption of single metal. Single-metal adsorptions were well described by multiple models of Freundlich isotherm with constant values of 0.21-0.432, Langmuir isotherm with constant values of 0.037-0.17, Pseudo-fist-order, Pseudo-second-order, and intra-particle diffusion (IPD). In conclusion, co-immobilization between GXCR, GO and AC can make metal removal more efficient. Adsorption capacity is increased with SSAs but not in the same proportion. Single-metal adsorptions involve multiple mechanisms of monolayer and multilayer adsorptions, external mass transfer, and IPD. IPD is important but not the only one rate-controlling step for single-metal adsorptions.

A bi-functional polymeric coating for the co-immobilization of proteins and peptides on microarray substrates

The analytical performance of the microarray technique in screening the affinity and reactivity of molecules towards a specific target, is highly affected by the coupling chemistry adopted to bind probes to the surface. However, the surface functionality limits the biomolecules that can be attached to the surface to a single type of molecule, thus forcing the execution of separate analyses to compare the performance of different species in recognizing their targets. Here we introduce a new N, N-dimethylacrylamide-based polymeric coating, bearing simultaneously different functionalities (N-acryloyloxysuccinimide and azide groups) to allow an easy and straightforward method to co-immobilize proteins and oriented peptides on the same substrate. The bi-functional copolymer has been obtained by partial post polymerization modification of the functional groups of a common precursor. A NMR characterization of the copolymer was conducted to quantify the percentage of NAS that has been transformed into azido groups. The polymer was used to coat surfaces onto which both native antibodies and alkyne modified peptides were immobilized, to perform the phenotype characterization of extracellular vesicles (EVs). This strategy represents a convenient method to reduce the number of analysis, thus possible systematic or random errors, besides offering a drastic shortage in time, reagents and costs.

Multi-enzyme co-immobilized nano-assemblies: Bringing enzymes together for expanding bio-catalysis scope to meet biotechnological challenges

Co-immobilization of multi-enzymes has emerged as a promising concept to design and signify bio-catalysis engineering. Undoubtedly, the existence and importance of basic immobilization methods such as encapsulation, covalent binding, cross-linking, or even simple adsorption cannot be ignored as they are the core of advanced co-immobilization strategies. Different strategies have been developed and deployed to green the twenty-first century bio-catalysis. Moreover, co-immobilization of multi-enzymes has successfully resolved the limitations of individual enzyme loaded constructs. With an added value of this advanced bio-catalysis engineering platform, designing, and fabricating co-immobilized enzymes loaded nanostructure carriers to perform a particular set of reactions with high catalytic turnover is of supreme interest. Herein, we spotlight the emergence of co-immobilization strategies by bringing multi-enzymes together with various types of nanocarriers to expand the bio-catalysis scope. Following a brief introduction, the first part of the review focuses on multienzyme co-immobilization strategies, i.e., random co-immobilization, compartmentalization, and positional co-immobilization. The second part comprehensively covers four major categories of nanocarriers, i.e., carbon based nanocarriers, polymer based nanocarriers, silica-based nanocarriers, and metal-based nanocarriers along with their particular examples. In each section, several critical factors that can affect the performance and successful deployment of co-immobilization of enzymes are given in this work.

Robust and recyclable magnetic nanobiocatalysts for extraction of anthocyanin from black rice

Anthocyanins, which are natural pigments and nutraceuticals, can be extracted from plant materials using enzyme-assisted methods. However, the enzymes used are often expensive, fragile, and hard to recover/reuse. In this study, cellulase and α-amylase were immobilized on amino-functionalized magnetic nanoparticles to prepare a magnetic nanobiocatalyst. The enzymes in this nanobiocatalyst exhibited higher stability and greater catalytic activity than free enzymes, including good thermal stability (50 to 70℃) and pH stability (pH 4.5-7.5). Nanobiocatalyst efficacy was demonstrated by extracting anthocyanins from black rice, with a maximum yield of 266 mg anthocyanin/100 g black rice obtained. After six reuse cycles, cellulase and α-amylase retained around 70% and 64% of their activity, respectively. Immobilization also increased their reusability. In summary, a novel magnetic nanobiocatalyst was developed for extracting anthocyanins from black rice, which may also have other applications within the food industry.

DNA derived N-doped 3D conductive network with enhanced electrocatalytic activity and stability for membrane-less biofuel cells

Enzymes are promising electrocatalysts in many biological processes. We proposed two strategies, co-immobilization and three-dimensional (3D) space design, to strengthen electron transfer (ET). In this research, DNA base and CNT were mixed in an aqueous solution; then the mixture was dried and ground. Finally, the powder was annealed in N₂ to obtain DNA derived N-doped 3D conductive network (N-G@CNT). N-G@CNT immobilized mediators on itself through adsorption. Such 3D space structure shows high activity toward a set of critical electrochemical reactions and high-performance in enzymatic biofuel cells (EBFCs). It is found that N-G@CNT conductive network possesses an interconnected porous structure and well-developed porosity. As a result, the membrane-less EBFCs equipped with enzyme/mediator co-immobilization N-G@CNT bioelectrodes were measured in a model 5 mM glucose-containing aqueous solution, human serum, and rabbit whole blood, respectively, which can generate 0.34, 0.078, and 0.15 mW cm^-2 power density, respectively. The constant-current discharge method carried out in a model 5 mM glucose-containing aqueous solution shows that the discharge time reached 19 h at a discharge current density of 0.01 mA cm^-2. The membrane EBFCs can deliver a high open circuit voltage of 0.68 V, a short-circuit current density of 2 mA cm^-2, and a maximum power density of 0.5 mW cm^-2.

Co-immobilized Alcohol Dehydrogenase and Glucose Dehydrogenase with Resin Extraction for Continuous Production of Chiral Diaryl Alcohol

Ni²⁺-functionalized porous ceramic/agarose composite beads (Ni-NTA Cerose) can be used as carrier materials to immobilize enzymes harboring a metal affinity tag. Here, a 6×His-tag fusion alcohol dehydrogenase Mu-S5 and glucose dehydrogenase from Bacillus megaterium (BmGDH) were co-immobilized on Ni-NTA Cerose to construct a packed bed reactor (PBR) for the continuous synthesis of the chiral intermediate (S)-(4-chlorophenyl)-(pyridin-2-yl) methanol ((S)-CPMA) NADPH recycling, and in situ product adsorption was achieved simultaneously by assembling a D101 macroporous resin column after the PBR. Using an optimum enzyme activity ratio of 2:1 (Mu-S5: BmGDH) and hydroxypropyl-β-cyclodextrin as co-solvent, a space-time yield of 1560 g/(L·d) could be achieved in the first three days at a flow rate of 5 mL/min and substrate concentration of 10 mM. With simplified selective adsorption and extraction procedures, (S)-CPMA was obtained in 84% isolated yield.

Improvement of biodiesel production from palm oil by co-immobilization of Thermomyces lanuginosa lipase and Candida antarctica lipase B: Optimization using response surface methodology

Candida antarctica lipase B (CALB) and Thermomyces lanuginose lipase (TLL) were co-immobilized on epoxy functionalized silica gel via an isocyanide-based multicomponent reaction. The immobilization process was carried out in water (pH 7) at 25 °C, rapidly (3 h) resulting in high immobilization yields (100%) with a loading of 10 mg enzyme/g support. The immobilized preparations were used to produce biodiesel by transesterification of palm oil. In an optimization study, response surface methodology (RSM) and central composite rotatable design (CCRD) methods were used to study the effect of five independent factors including temperature, methanol to oil ratio, t-butanol concentration and CALB:TLL ratio on the yield of biodiesel production. The optimum combinations for the reaction were CALB:TLL ratio (2.1:1), t-butanol (45 wt%), temperature (47 °C), methanol: oil ratio (2.3). This resulted in a FAME yield of 94%, very close to the predicted value of 98%.

One pot clarification and debittering of grapefruit juice using co-immobilized enzymes@chitosanMNPs

In the present work, enzymes pectinase and naringinase were simultaneously co-immobilized on an eco-friendly chitosan coated magnetic nanoparticles (chitosanMNPs) by cross-linking using chitosan as a macro-molecular cross-linker. The maximum activity recovery of both enzymes in the co-immobilized form was obtained at chitosanMNPs to enzymes ratio of 1:3, 3% cross-linker concentration and 150 min cross-linking time. The synthesized MNPs before and after co-immobilization were characterized using different techniques. The prepared biocatalyst was found spherical with an average size below 200 nm and showed supermagnetic property with saturation magnetization of 38.28 emu/g. The optimum pH and temperature of both enzymes in co-immobilized form was found at 5.5 and 65 °C. The prepared biocatalyst exhibited an improved thermal stability with 1.8-fold increase in the half-life. The secondary structural analysis revealed that, prepared co-immobilized biocatalyst undergone changes in the conformational and structural rigidity due to macro-molecular cross-linker. The co-immobilized biocatalysts were evaluated for one pot clarification and debittering of grapefruit juice and found ~52% reduction in turbidity and ~85% reduction in the naringin content. The co-immobilized enzymes were recycled up to 7^th cycle and can be easily stored at room temperature for 30 days retaining up to 64% and 86% residual activities respectively.

Construction and Application of PLP Self-sufficient Biocatalysis System for Threonine Aldolase

A number of organic synthesis involve threonine aldolase (TA), a pyridoxal phosphate (PLP)-dependent enzyme. Although the addition of exogenous PLP is necessary for the reactions, it increases the cost and complicates the purification of the product. This work constructed a PLP self-sufficient biocatalysis system for TA, which included an improvement of the intracellular PLP level and co-immobilization of TA with PLP. Engineered strain BL-ST was constructed by introducing PLP synthase PdxS/T to Escherichia coli BL21(ED3). The intracellular PLP concentration of the strain increased approximately fivefold to 48.5 μmol/g_DCW. l-TA, from Bacillus nealsonii (BnLTA), was co-expressed in the strain BL-ST with PdxS/T, resulting in the engineered strain BL-BnLTA-ST. Compared with the control strain BL-BnLTA (254.1 U/L), the enzyme activity of the strain BL-BnLTA-ST reached 1518.4 U/L without the addition of exogenous PLP. An efficient co-immobilization system was then designed. The epoxy resin LX-1000HFA wrapped by polyethyleneimine (PEI) acted as a carrier to immobilize the crude enzyme solution of the strain BL-BnLTA-ST mixed with an extra 100 μM of exogenous PLP, resulting in the catalyst HFA^PEI-BnLTA-STPLP 100. HFA^PEI-BnLTA-STPLP 100 exhibited a half-life of approximately 450 h, and the application of the catalyst in the continuous biosynthesis of 3-[4-(methylsulfonyl) phenyl] serine had more than 180 batch reactions (>60%_conv) without the extra addition of exogenous PLP. The excellent compatibility and stability of the system were further confirmed by other TAs. This work introduced a PLP self-sufficient biocatalysis system that can reduce the cost of PLP and contribute to the industrial application of TA. In addition, the system may also be applied in other PLP-dependent enzymes.

Improving the biocatalytic performance of co-immobilized cells harboring nitrilase via addition of silica and calcium carbonate

To improve nicotinic acid (NA) yield and meet industrial application requirements of sodium alginate-polyvinyl alcohol (SA-PVA) immobilized cells of Pseudomonas putida mut-D3 harboring nitrilase, inorganic materials were added to the SA-PVA immobilized cells to improve mechanical strength and mass transfer performance. The concentrations of inorganic materials were optimized to be 2.0% silica and 0.6% CaCO₃. The optimal pH and temperature for SA-PVA immobilized cells and composite immobilized cells were both 8.0 and 45 °C, respectively. The half-lives of composite immobilized cells were 271.48, 150.92, 92.92 and 33.12 h, which were 1.40-, 1.35-, 1.22- and 1.63-fold compared to SA-PVA immobilized cells, respectively. The storage stability of the composite immobilized cells was slightly increased. The composite immobilized cells could convert 14 batches of 3-cyanopyridine with feeding concentration of 250 mM and accumulate 418 g ·L^-1 nicotinic acid, while the SA-PVA immobilized cells accumulated 346 g L^-1 nicotinic acid.

Integration of sodium hypochlorite pretreatment with co-immobilized microalgae/bacteria treatment of meat processing wastewater

Wastewater with 0.2, 0.4, 0.8, 1.0 mg/L free chlorine was biologically treated using co-immobilized microalgae/bacteria. In contrast, non-pretreated wastewater was treated with beads (control) and blank beads (blank) under the same operating condition. Results showed that NaClO pretreatment removed 8-33% total nitrogen (TN), 31-45% true color and 0.7-2.5 log CFU/mL aerobic-bacteria. At the end of treatment, maximum algal biomass (2,027 dry weight mg/L) was achieved with 0.2 mg/L free chlorine. Bacterial growth in wastewater was decreased by NaClO pretreatment before reaching 7.2-7.7 log CFU/mL on the fifth day. Beads with microorganisms (control) removed 15% more chemical-oxygen-demand (COD), 16% more TN, and 13% more total phosphate (PO₄^3-) than blank. Pretreatment with 0.2 mg/L free chlorine increased TN removal from 75% to 80% while pollutants removal was substantially decreased with 0.4-1.0 mg/L free chlorine. Considering algal biomass growth and pollutants removal, 0.2 mg/L free chlorine pretreatment was recommended for microalgae/bacteria co-immobilized system.

Sensitive immunosensor based on high effective resonance energy transfer of lucigenin to the cathodic electrochemiluminescence of tris(bipyridine) Ru(II) complex

Electrochemiluminescence resonance energy transfer (ECL-RET) has been attracting much focus as an effective approach for great ECL enhancement. Here, we found that lucigenin (Luc) could serve as a new energy transfer donor and greatly improve the cathodic ECL of bis(2,2'-bipyridyl)(4'-methyl-[2,2']bipyridinyl-4-carboxylicacid) ruthenium(II) (Ru(Bpy)₂(Mcbpy)²⁺, acceptor). Then, both Luc and Ru(Bpy)₂(Mcbpy)²⁺ were largely co-immobilized onto the PdCu nanocrystals and polyethyleneimine (PEI) modified single-walled carbon nanohorns (SWCNHs-PdCuNCs-PEI) through π-π stacking and crosslinking reaction, respectively. By this way, the excellent electrocatalytic behavior and high loading capability for both Luc and Ru(Bpy)₂(Mcbpy)²⁺ of SWCNHs-PdCuNCs-PEI effectively facilitated the ECL reaction. Particularly, the co-immobilization strategy making the donor (Luc)/acceptor (Ru(Bpy)₂(Mcbpy)²⁺) pairs co-exist in the same nano-composite could obviously increase the ECL-RET efficiency by shortening the electron-transfer path and reducing energy loss, further significantly improving the ECL signal. Combining the obtained nano-composite (Luc-SWCNHs-PdCuNCs-PEI-Ru(Bpy)₂(Mcbpy)²⁺) with sandwiched immunoreaction, an ECL immunosensor was constructed for β2-microglobulin (β2-M) measurement. And as a result, it exhibited excellent performance in sensitivity, stability and selectivity. The establishment of the new effective donor/acceptor pairs for ECL-RET and the co-immobilization strategy of making those donor/acceptor pairs largely co-exist in the same nano-composite would greatly improve the ECL efficiency and motivate the wider application of ECL technology.

A genetically-encoded synthetic self-assembled multienzyme complex of lipase and P450 fatty acid decarboxylase for efficient bioproduction of fatty alkenes

We develop an efficient and economic cascade multienzymes for fatty alkene bioproduction based on the lipase hydrolysis coupled to the P450 decarboxylation in the form of multiple enzyme complex. One step preparation of a multienzyme complex was based on a mixture of cell extracts including dockerin-enzyme fusions and one cohesin-cellulose binding module (CBM) fusion through high specific interaction of dockerin and cohesin. Simultaneously, the CBM was bound to cellulose carrier to form co-immobilized multienzyme. The key factors affecting overall efficiency of alkene bioproduction including substrate channeling of hydrolysis and decarboxylation, the ratio and position of two enzymes, stability were all addressed by genetically engineering of the synthetic CBM-cohesin fusions. The multienzymes exhibited more than 9.2 fold enhancement in initial reaction rate and much higher conversion yields (69%-72%) compared to mixture of free enzyme counterpart. The enzymatic cascade based multienzymes could efficiently convert renewable triglycerides to alkenes.

Development of co-immobilized tri-enzyme biocatalytic system for one-pot pretreatment of four different perennial lignocellulosic biomass and evaluation of their bioethanol production potential

Today, many researchers are focusing on research for alternative promising energy sources and sustainable technology for bioethanol production to meet the increasing global energy demand. Here, we develop a novel one-pot pretreatment technology by co-immobilizing laccase, cellulase and β-glucosidase to act as a tri-enzyme biocatalyst for evaluating the bioethanol production potential of four sustainable lignocellulosic biomasses viz., Typha angustifolia, Arundo donax, Saccharum arundinaceum, and Ipomoea carnea. The co-immobilized enzyme system was more stable at different temperatures and at longer storage, compared to free enzyme. During enzymatic saccharification, Saccharum arundinaceum showed higher total reducing sugar of 205 ± 3.73 mg/g when compared to other biomass. The highest percentage of bioethanol yield of 63.43 ± 9.35% was obtained with Ipomoea carnea. The effects of co-immobilized tri-enzyme biocatalyst on the biomasses were evaluated. The results revealed that the co-immobilized tri-enzyme biocatalyst could act as effective one-pot pretreatment for the production of bioethanol from lignocellulosic biomass.

Co-immobilization of cellulase and lysozyme on amino-functionalized magnetic nanoparticles: An activity-tunable biocatalyst for extraction of lipids from microalgae

An activity-tunable biocatalyst for Nannochloropsis sp. cell-walls degradation was prepared by co-immobilization of cellulase and lysozyme on the surface of amino-functionalized magnetic nanoparticles (MNPs) employing glutaraldehyde. The competition between cellulase and lysozyme during immobilization was caused by the limited active sites of the MNPs. The maximum recovery of activities (cellulase: 78.9% and lysozyme: 69.6%) were achieved due to synergistic effects during dual-enzyme co-immobilization. The thermal stability in terms of half-life of the co-immobilized enzymes was three times higher than that in free form and had higher catalytic efficiency for hydrolysis of cell walls. Moreover, the co-immobilized enzymes showed greater thermal stability and wider pH tolerance than free enzymes under harsh conditions. Furthermore, the co-immobilized enzymes retained up to 60% of the residual activity after being recycled 6 times. This study provides a feasible approach for the industrialization of enzyme during cell-walls disruption and lipids extraction from Nannochloropsis sp.

Efficient Production of Prebiotic Gluco-oligosaccharides in Orange Juice Using Immobilized and Co-immobilized Dextransucrase

Dextransucrase from Leuconostoc mesenteroides NRRL B-512F was subjected to immobilization and co-immobilization with dextranase from Chaetomium erraticum. Immobilization has enhanced the operational and storage stability of dextransucrase. Two hundred milligrammes (2.4 IU/mg) of alginate beads (immobilized and co-immobilized) were found to be optimum for the production of gluco-oligosaccharides (GOS) in orange juice with a high degree of polymerization. The pulp of the orange juice did not interfere in the reaction. In the batch process, co-immobilized dextransucrase (41 g/L) produced a significantly higher amount of GOS than immobilized dextransucrase (37 g/L). Alginate entrapment enhanced the thermal stability of dextransucrase for up to 3 days in orange juice at 30 °C. The production of GOS in semi-continuous process was 39 g/L in co-immobilized dextransucrase and 33 g/L in immobilized dextransucrase. Thus, immobilization technology offers a great scope in terms of reusability and efficient production of a value added functional health drink.

Co-encapsulation of amyloglucosidase with starch and Saccharomyces cerevisiae as basis for a long-lasting CO2 release

CO₂ is known as a major attractant for many arthropod pests which can be exploited for pest control within novel attract-and-kill strategies. This study reports on the development of a slow-release system for CO₂ based on calcium alginate beads containing granular corn starch, amyloglucosidase and Saccharomyces cerevisiae. Our aim was to evaluate the conditions which influence the CO₂ release and to clarify the biochemical reactions taking place within the beads. The amyloglucosidase was immobilized with a high encapsulation efficiency of 87% in Ca-alginate beads supplemented with corn starch and S. cerevisiae biomass. The CO₂ release from the beads was shown to be significantly affected by the concentration of amyloglucosidase and corn starch within the beads as well as by the incubation temperature. Beads prepared with 0.1 amyloglucosidase units/g matrix solution led to a long-lasting CO₂ emission at temperatures between 6 and 25 °C. Starch degradation data correlated well with the CO₂ release from beads during incubation and scanning electron microscopy micrographs visualized the degradation of corn starch granules by the co-encapsulated amyloglucosidase. By implementing MALDI-ToF mass spectrometry imaging for the analysis of Ca-alginate beads, we verified that the encapsulated amyloglucosidase converts starch into glucose which is immediately consumed by S. cerevisiae cells. When applied into the soil, the beads increased the CO₂ concentration in soil significantly. Finally, we demonstrated that dried beads showed a CO₂ production in soil comparable to the moist beads. The long-lasting CO₂-releasing beads will pave the way towards novel attract-and-kill strategies in pest control.

Co-immobilization of adhesive peptides and VEGF within a dextran-based coating for vascular applications

Multifunctional constructs providing a proper environment for adhesion and growth of selected cell types are needed for most tissue engineering and regenerative medicine applications. In this context, vinylsulfone (VS)-modified dextran was proposed as a matrix featuring low-fouling properties as well as multiple versatile moieties. The displayed VS groups could indeed react with thiol, amine or hydroxyl groups, be it for surface grafting, crosslinking or subsequent tethering of biomolecules. In the present study, a library of dextran-VS was produced, grafted to aminated substrates and characterized in terms of degree of VS modification (%VS), cell-repelling properties and potential for the oriented grafting of cysteine-tagged peptides. As a bioactive coating of vascular implants, ECM peptides (e.g. RGD) as well as vascular endothelial growth factor (VEGF) were co-immobilized on one of the most suitable dextran-VS coating (%VS=ca. 50% of saccharides units). Both RGD and VEGF were efficiently tethered at high densities (ca. 1nmol/cm(2) and 50fmol/cm(2), respectively), and were able to promote endothelial cell adhesion as well as proliferation. The latter was enhanced to the same extent as with soluble VEGF and proved selective to endothelial cells over smooth muscle cells. Altogether, multiple biomolecules could be efficiently incorporated into a dextran-VS construct, while maintaining their respective biological activity.

STATEMENT OF SIGNIFICANCE

This work addresses the need for multifunctional coatings and selective cell response inherent to many tissue engineering and regenerative medicine applications, for instance, vascular graft. More specifically, a library of dextrans was first generated through vinylsulfone (VS) modification. Thoroughly selected dextran-VS provided an ideal platform for unbiased study of cell response to covalently grafted biomolecules. Considering that processes such as healing and angiogenesis require multiple factors acting synergistically, vascular endothelial growth factor (VEGF) was then co-immobilized with the cell adhesive RGD peptide within our dextran coating through a relevant strategy featuring orientation and specificity. Altogether, both adhesive and proliferative cues could be incorporated into our construct with additive, if not synergetic, effects.

Amperometric determination of serum total cholesterol with nanoparticles of cholesterol esterase and cholesterol oxidase

We describe the preparation of glutaraldehyde cross-linked and functionalized cholesterol esterase nanoparticles (ChENPs) and cholesterol oxidase nanoparticles (ChOxNPs) aggregates and their co-immobilization onto Au electrode for improved amperometric determination of serum total cholesterol. Transmission electron microscope (TEM) images of ChENPs and ChOxNPs showed their spherical shape and average size of 35.40 and 56.97 nm, respectively. Scanning electron microscope (SEM) studies of Au electrode confirmed the co-immobilization of enzyme nanoparticles (ENPs). The biosensor exhibited optimal response at pH 5.5 and 40°C within 5 s when polarized at +0.25 V versus Ag/AgCl. The working/linear range of the biosensor was 10-700 mg/dl for cholesterol. The sensor showed high sensitivity and measured total cholesterol as low as 0.1 mg/dl. The biosensor was evaluated and employed for total cholesterol determination in sera of apparently healthy and diseased persons. The analytical recovery of added cholesterol was 90%, whereas the within-batch and between-batch coefficients of variation (CVs) were less than 2% and less than 3%. There was a good correlation (r = 0.99) between serum cholesterol values as measured by the standard enzymic colorimetric method and the current method. The initial activity of ENPs/working electrode was reduced by 50% during its regular use (200 times) over a period of 60 days when stored dry at 4°C.

Controlled co-immobilization of EGF and VEGF to optimize vascular cell survival

Growth factors (GFs) are potent signaling molecules that act in a coordinated manner in physiological processes such as tissue healing or angiogenesis. Co-immobilizing GFs on materials while preserving their bioactivity still represents a major challenge in the field of tissue regeneration and bioactive implants. In this study, we explore the potential of an oriented immobilization technique based on two high affinity peptides, namely the Ecoil and Kcoil, to allow for the simultaneous capture of the epidermal growth factor (EGF) and the vascular endothelial growth factor (VEGF) on a chondroitin sulfate coating. This glycosaminoglycan layer was selected as it promotes cell adhesion but reduces non-specific adsorption of plasma proteins. We demonstrate here that both Ecoil-tagged GFs can be successfully immobilized on chondroitin sulfate surfaces that had been pre-decorated with the Kcoil peptide. As shown by direct ELISA, changing the incubation concentration of the various GFs enabled to control their grafted amount. Moreover, cell survival studies with endothelial and smooth muscle cells confirmed that our oriented tethering strategy preserved GF bioactivity. Of salient interest, co-immobilizing EGF and VEGF led to better cell survival compared to each GF captured alone, suggesting a synergistic effect of these GFs. Altogether, these results demonstrate the potential of coiled-coil oriented GF tethering for the co-immobilization of macromolecules; it thus open the way to the generation of biomaterials surfaces with fine-tuned biological properties.

STATEMENT OF SIGNIFICANCE

Growth factors are potent signaling molecules that act in a coordinated manner in physiological processes such as tissue healing or angiogenesis. Controlled coimmobilization of growth factors on biomaterials while preserving their bioactivity represents a major challenge in the field of tissue regeneration and bioactive implants. This study demonstrates the potential of an oriented immobilization technique based on two high affinity peptides to allow for the simultaneous capture of epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF). Our system allowed an efficient control on growth factor immobilization by adjusting the incubation concentrations of EGF and VEGF. Of salient interest, co-immobilizing of specific ratios of EGF and VEGF demonstrated a synergistic effect on cell survival compared to each GF captured alone.

A Ca-alginate particle co-immobilized with Phanerochaete chrysosporium cells and the combined cross-linked enzyme aggregates from Trametes versicolor

For improving stability of immobilized white-rot fungus to treat various effluents, Phanerochaete chrysosporium cells and the combined cross-link enzyme aggregates (combi-CLEAs) prepared from Trametes versicolor were co-immobilized into the Ca-alginate gel particles in this paper. The activity yields of obtained combi-CLEAs were 42.7% for lignin peroxidases (LiPs), 31.4% for manganese peroxidases (MnPs) and 40.4% for laccase (Lac), respectively. And their specific activities were 30.2U/g as combi-CLEAs-LiPs, 9.5 U/g as combi-CLEAs-MnPs and 28.4 U/g as combi-CLEAs-Lac. Further, the present of the combi-CLEAs in the particles extremely improved their ability to degrade the dyes. Compared to the immobilized Ph. chrysosporium without the combi-CLEAs, the co-immobilized particles enhanced the decolorized rate of Acid Violet 7 (from 45.2% to 93.4%) and Basic Fuchsin (from 12.1% to 67.9%). In addition, the addition of the combi-CLEAs improved the adaptability of the white-rot fungal particles to adverse environmental conditions.

A sandwich-type electrochemical immunosensor for carcinoembryonic antigen based on signal amplification strategy of optimized ferrocene functionalized Fe₃O₄@SiO₂ as labels

A sandwich-type electrochemical immunosensor was developed for sensitive detection of carcinoembryonic antigen (CEA) by using ferroferric oxide@silica-amino groups (Fe3O4@SiO2-NH2) as carriers and gold nanoparticles-graphene oxide (GO-AuNPs) as platform. The Fe3O4@SiO2-NH2 surface was used as linked reagents for co-immobilization of ferrocenecarboxylic acid (Fc-COOH) and secondary anti-CEA (Ab2) to prepare the signal probe, and it also could hasten the decomposition of hydrogen peroxide (H2O2) to amplify signals. Differential pulse voltammetry (DPV) was successfully used to quantify CEA. Under the optimized conditions, the designed immunosensor shows an excellent analytical performance wide dynamic response range of CEA concentration from 0.001 ng mL(-1) to 80 ng mL(-1) with a relatively low detection limit of 0.0002 ng mL(-1) (S/N=3), and high specificity and good reproducibility. The proposed immunosensor was successfully used to determine CEA in spiked human serum samples.

Ethanol production from wheat straw by Saccharomyces cerevisiae and Scheffersomyces stipitis co-culture in batch and continuous system

In this research, Scheffersomyces stipitis and Saccharomyces cerevisiae in immobilized and suspended state were used to convert pentose and hexose sugars to ethanol. In batch and continuous systems, S. stipitis and S. cerevisiae co-culture performance was better than S. cerevisiae. Continuous ethanol production was performed in packed bed immobilized cell reactor (ICR). In ICR, S. stipitis cells were found to be more sensitive to oxygen concentration and other possible mass transfer limitations as compared to S. cerevisiae. Use of co-immobilized S. stipitis and S. cerevisiae resulted in maximum xylose consumption (73.92%) and 41.68 g/L day ethanol was produced at HRT (hydraulic retention time) of 6h with wheat straw hydrolysate. At HRT of 0.75 h, the highest amount of ethanol with the values of 356.21 and 235.43 g/L day was produced when synthetic medium and wheat straw hydrolysate were used as feeding medium in ICR, respectively.

A self-sufficient Baeyer-Villiger biocatalysis system for the synthesis of ɛ-caprolactone from cyclohexanol

In order to establish a new route for ɛ-caprolactone production from the corresponding cyclohexanol with an internal cofactor recycling for NADPH, a recently redesigned thermostable polyol dehydrogenase (PDH) and the cyclohexanone monooxygenase (CHMO) from Acinetobacter calcoaceticus were combined. First, the expression of PDH could be improved 4.9-fold using E. coli C41 with co-expression of chaperones. Both enzymes were also successfully co-immobilized on glutaraldehyde-activated support (Relizyme™ HA403). Cyclohexanol could be converted to ɛ-caprolactone (ɛ-CL) with 83% conversion using the free enzymes and with 34% conversion using the co-immobilized catalysts. Additionally, a preparative scale biotransformation of ɛ-caprolactone starting from cyclohexanol was performed using the soluble enzymes. The ɛ-CL could be isolated by simple extraction and evaporation with a yield of 55% and a purity of >99%.