Valorization of Waste Cooking Oil into Biodiesel via Bacillus stratosphericus Lipase Amine-Functionalized Mesoporous SBA-15 Nanobiocatalyst

In this study, evaporation-induced self-assembly was applied to prepare amine-functionalized nano-silica (NH2-Pr-SBA-15). That was simply used to immobilize Bacillus stratosphericus PSP8 lipase (E–NH2–Pr-SBA-15), producing a nanobiocatalyst with good stability under vigorous shaking and a maximum lipase activity of 45 ± 2 U/mL. High-resolution X-ray diffractometer, Fourier transform infrared spectroscopy, N2 adsorption-desorption, field-emission scanning electron, and high-resolution transmission electron microscopic analyses proved the successful SBA-15 functionalization and enzyme immobilization. Response surface methodology based on a 1/2 fraction-three-levels face center composite design was applied to optimize the biodiesel transesterification process. This expressed efficient percentage conversion (97.85%) and biodiesel yield (97.01%) under relatively mild operating conditions: 3.12 : 1 methanol to oil ratio, 3.08 wt.% E–NH2–Pr-SBA-15 loading, 48.6°C, 3.19 h at a mixing rate of 495.53 rpm. E–NH2–Pr-SBA-15 proved to have a long lifetime, operational stability, and reusability.

Lipase immobilization via cross-linked enzyme aggregates: Problems and prospects - A review

In this review we have focused on the preparation of cross-linked enzyme aggregates (CLEAs) from lipases, as these are among the most used enzyme in bioprocesses. This immobilization method is considered very attractive due to preparation simplicity, non-use of supports and the possibility of using crude enzyme extracts. CLEAs provide lipase stabilization under extreme temperature or pH conditions or in the presence of organic solvents, in addition to preventing enzyme leaching in aqueous medium. However, it presents some problems in the preparation and limitations in their use. The problems in preparation refer mainly to the crosslinking step, and may be solved using an aminated feeder. The problems in handling have been tackled designing magnetic-CLEAs or trapping the CLEAs in particles with better mechanical properties, the substrate diffusion problems has been reduced by producing more porous-CLEAs, etc. The enzyme co-immobilization using combi-CLEAs is also a new tendency. Therefore, this review explores the CLEAs methodology aimed at lipase immobilization and its applications.

Regulated Polyelectrolyte Nanogels for Enzyme Encapsulation and Activation

Polyelectrolyte (PE) nanogels consisting of cross-linked PE networks integrate the advanced features of both nanogels and PEs. The soft environment and abundant intrinsic charges are of special interest for enzyme immobilization. However, the crucial factors that regulate enzyme encapsulation and activation remain obscure to date. Herein, we synthesized cationic poly (dimethyl aminoethyl methacrylate), PDMAEMA, nanogels with well-defined size and cross-link degrees and fully investigated the effects of different control factors on lipase immobilization. We demonstrate that the cationic PDMAEMA nanogels indeed enable efficient and safe loading of anionic lipase without disturbing their structures. Strong charge interaction achieved by tuning pH and larger particle size are favorable for lipase loading, while the enhanced enzymatic activity demands nanogels with smaller size and a moderate cross-link degree. As such, PDMAEMA nanogels with a hydrodynamic radius of 35 nm and 30% cross-linker fraction display the optimal catalytic efficiency, which is fourfold of that of free lipase. Moreover, the immobilization endows enhanced enzymatic activity in a broad scope of pH, ionic strength, and temperature, demonstrating effective protection and activation of lipase by the designed nanogels. Our study validates the crucial controls of the size and structure of PE nanogels on enzyme encapsulation and activation, and the revealed findings shall be helpful for designing functional PE nanogels and boosting their applications for enzyme immobilization.

Preparation of sulfhydryl functionalized magnetic SBA-15 and its high-efficiency adsorption on uranyl ion in solution

A novel assembly method was used to prepare the sulfhydryl functionalized magnetic SBA-15 (SH-M-SBA-15). The physicochemical properties of SH-M-SBA-15 were characterized by TEM, XRD, EDS, FT-IR, BET, and VSM. Batch adsorption experiments were conducted to investigate the influence of initial uranium concentration, dosage of adsorbent, pH values, contact time, and temperature on the adsorption efficiency and behaviors. The adsorption types were analyzed from the aspects of kinetic, isotherms, and thermodynamic. The results show that the specific surface area of SH-M-SBA-15 is 316.67 m²/g, which is smaller than that of SBA-15 (692.18 m²/g). However, compared with SBA-15, SH-M-SBA-15 has more surface sulfhydryl functional groups. The addition of this group can improve the adsorption of uranyl ions by SH-M-SBA-15. The optimal adsorption conditions were adsorption dosage 40 mg/L, pH 6, temperature 35 °C, contact time 180 min, and initial uranium concentration 35 mg/L. Under this condition, the maximum adsorption amount of uranyl ion by SH-M-SBA-15 can reach 804.79 mg/g, which is much higher than the highest adsorption capacity of uranyl ion by SBA-15 (146.23 mg/g). The adsorption process was better depicted by the Langmuir isotherm model. The process was consistent with the quasi-second-order model. ΔG was negative and ΔH was positive, indicating spontaneous and endothermic adsorption.

Combined Cross-Linked Enzyme Aggregates of Monoamine Oxidase and Putrescine Oxidase as a Bifunctional Biocatalyst for Determination of Biogenic Amines in Foods

In order to determine total biogenic amines in fermented foods, the combined cross-linked enzyme aggregates of a monoamine oxidase and a putrescine oxidase (combi-CLEAs) and the cross-linked enzyme aggregates (CLEAs) of the fused enzyme of two amine oxidases (MonoAmine Putrescien Oxidase, MAPO) were prepared. The effects of various parameters were examined to optimize the CLEAs formation. Biochemical characterization and stability of free and the CLEAs enzymes were performed. Through optimization of the CLEAs formation condition, the combi-CLEAs and the CLEAs-MAPO were prepared with 82% and 78% of residual activities relative to the activities of the subjected enzymes were in a preparative scale. The optimal pH for tyramine-activities of the CLEAs enzymes were shifted to relatively basic pH, leading to synchronization of the optimal performances of combi-CLEAs over pH for tyramine and putrescine. In addition, thermostability of the CLEAs enzymes were improved with almost double half-lives at 65 °C in comparison to the free enzymes. The catalytic efficiencies of combi-CLEAs for tyramine, histamine and putrescine were reduced by 41%, 56%, and 31%, respectively, and the inhibition potency by the substrate was reduced by two-fold in comparison of the mixed free enzymes. In conclusion, combi-CLEAs are a promising catalyst with the improved stability and the same optimum pH for dual activities in enzymatic determination of biogenic amines in foods.

Naturally-derived biopolymers: Potential platforms for enzyme immobilization

Naturally-derived biopolymers such as alginate, chitosan, cellulose, agarose, guar gum/guaran, agar, carrageenan, gelatin, dextran, xanthan, and pectins, etc. have appealed significant attention over the past several years owing to their natural abundance and availability all over the years, around the globe. In addition, their versatile properties such as non-toxicity, biocompatibility, biodegradability, flexibility, renewability, and the availability of numerous reactive sites offer significant functionalities with multipurpose applications. At present, intensive research efforts have been focused on engineering enzymes using natural biopolymers as novel support/composite materials for diverse applications in biomedical, environmental, pharmaceutical, food and biofuel/energy sectors. Immobilization appears as a straightforward and promising approach to developing biocatalysts with improved catalytic properties as compared to their free counterparts. Biopolymers-assisted enzymes are more stable, robust, and recoverable than that of free forms, and can be employed for continuous biocatalytic reactions. The present review highlights the recent developments and use of biopolymers and their advanced composites as support carriers for the immobilization of a variety of different enzymes to develop biocatalysts with desired catalytic activity and stability characteristics for emerging applications.

Norepinephrine-functionalised nanoflower-like organic silica as a new adsorbent for effective Pb(II) removal from aqueous solutions

In order to remove Pb(II) ions efficiently from aqueous solutions, a new effective adsorbent of norepinephrine-functionalised nanoflower-like organic silica (NE-NFOS) was synthesised by a biomimetic method. Biomimetic functionalization with norepinephrine has the advantages of environment-friendly and easy operation. Characterization of the NE-NFOS using scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller method, and Fourier-transform infrared spectroscopy revealed that the NFOS was modified successfully by norepinephrine. Furthermore, the influences of different parameters including adsorption kinetics, solution pH, adsorption isotherms, concentrations of Na+, K+, Ca2+, and Mg2+, desorption and reusability were studied. The adsorption experiments showed that the capacity of NE-NFOS to adsorb Pb(II) ions improved greatly after functionalisation and adsorption equilibrium was attained within 90 min at a pH of 6.0. The Na+, K+, Ca2+, and Mg2+ concentrations had little influence on the adsorption, and after recycling for five times, the Pb(II) ion removal efficiency of the adsorbent was more than 79% of its initial value. Thus, it was demonstrated that the NE-NFOS with excellent adsorption performance could be a suitable adsorbent for Pb(II) ions removal in practical applications.

Exquisite stability and catalytic performance of immobilized lipase on novel fabricated nanocellulose fused polypyrrole/graphene oxide nanocomposite: Characterization and application

This work was performed to describe the facile procedure of a novel nanobiocatalyst, nano cellulose fused polypyrrole/graphene oxide nanocomposite for the efficacious immobilization of lipase, a versatile hydrolytic enzyme having potential applications in industries. The fabricated nanocomposite was characterized using Fourier transform infrared spectroscopy, differential thermal analysis, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and Candida rugosa lipase was immobilized onto nanocomposite through physical adsorption. The catalytic efficiency and operational stabilities of immobilized lipase were improved significantly compared to the free lipase. The reusability profile outcomes showed that the immobilized lipase formulation was an outstanding nanobiocatalyst as it retained 85% of its original catalytic activity after 10 cycles of application. The nanobiocatalyst was employed for the synthesis of the fruit flavour compound, ethyl acetoacetate. The immobilized lipase successfully synthesised flavour compound in solvent free media and n-hexane having 27.5% and 75.5% ester yields respectively. Moreover, these outcomes demonstrating graphene oxide modified carrier induced stabilization, amended solvent tolerance and operational stability of immobilized enzyme, will have quintessential influence on practical scale up of biotechnological industries.

Conversion of levulinic acid into alkyl levulinates: Using lipase immobilized on meso-molding three-dimensional macroporous organosilica as catalyst

For conversion of biomass-derived levulinic acid into alkyl levulinates, a novel kind of lipase-based biocatalyst was prepared through immobilized lipase B from C. antarctica (CALB) on organosilica material with highly ordered 3D macroporous organosilica frameworks and a 2D hexagonal meso-structure (named 3DOM/m-OS) for the first time. The catalytic performance of the immobilized lipase (NER@3DOM/m-OS) was investigated. NER@3DOM/m-OS was used as biocatalyst to catalyze the esterification reaction between levulinic acid (LA) and n-butanol. Under optimized reaction conditions, 74.59% of ester yield was achieved after 12h of reaction. NER@3DOM/m-OS was also used to production of other alkyl levulinates, the ester yields increased to 84.51% (octyl levulinate) and 91.14% (dodecyl levulinate), respectively. When NER@3DOM/m-OS was used repeatedly in batch reactions, the ester yields of n-butyl, octyl, and dodecyl levulinate could retain 46.18%, 82.33% and 81.25% after 9 reaction cycles, respectively, which was better than commercial lipase Novozym 435 under the same condition.

Biomimetic-Functionalized, Tannic Acid-Templated Mesoporous Silica as a New Support for Immobilization of NHase

Tannic acid-templated mesoporous silica (TAMS) was synthesized using a simple nonsurfactant template method and dopamine-functionalized TAMS (Dop-TAMS), which was prepared via a biomimetic coating, was developed as a new support for immobilization of NHase (NHase@Dop-TAMS). The Dop-TAMS was thoroughly characterized by the transmission electron microscopy (TEM), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), and Fourier transform infrared (FT-IR) and the results showed that the Dop-TAMS possessed sufficiently large pore size and volume for the accommodation of NHase. Studying the thermal stability, storage, shaking stability, and pH stability of the free and immobilized NHase indicated that the catalytic properties of NHase@Dop-TAMS were significantly enhanced. Moreover, the NHase@Dop-TAMS exhibited good reusability. All the results demonstrated that Dop-TAMS could be used as an excellent matrix for the immobilization of NHase.

Dopamine-functionalized mesoporous onion-like silica as a new matrix for immobilization of lipase Candida sp. 99-125

Dopmine functionalized mesoporous onion-like silica (DPMS) was synthesized via a biomimetic coating, and lipase Candida sp. 99-125 (LCS) was immobilized in DPMS (LCS@DPMS) by physical adsorption in this study. The DPMS was characterized by SEM, TEM, BET and FT-IR, and it was shown that the DPMS had clear multishell structures with large surface area of 419 m2/g. The activity, pH stability, thermal stability, storage stability, and reusability of the LCS@DPMS were investigated in detail. The stabilities of LCS@DPMS were improved significantly compared to the free lipase and LCS@MS (LCS immobilized in unfunctionalized mesoporous onion-like silica by physical adsorption). All the results indicated that the DPMS had high efficiency and improved stability for lipase immobilization.

Adsorptive removal of Ni(ii) ions from aqueous solution and the synthesis of a Ni-doped ceramic: an efficient enzyme carrier exhibiting enhanced activity of immobilized lipase

We report the successful removal of Ni²⁺ from aqueous solution via entrapment by chitosan nanoparticles, followed by calcination with a ceramic matrix to construct a novel carrier for lipase immobilization with enhanced activity.

Facile functionalized of SBA-15 via a biomimetic coating and its application in efficient removal of uranium ions from aqueous solution

A novel dopamine-functionalized mesoporous silica (DMS), synthesized by grafting dopamine onto a mesoporous molecular sieve (SBA-15), was developed as a sorbent to extract U(VI) from aqueous solution. The method used to modify SBA-15 was simple, facile and cost-effective. The DMS was characterized by SEM, TEM, XRD and BET, showing that the material had an ordered mesoporous structure and a large surface area. The effect of contact time, pH, ionic strength, temperature, and solid-liquid ratio on the sorption process was investigated. It was demonstrated that the adsorption of U(VI) by DMS was fast and that it can be described by the pseudo-second order-equation where the equilibrium time was 20 min. Additionally, the adsorption isotherm data were fitted well by the Langmuir model with the maximum adsorption capacity of DMS of 196 mg/g at pH 6.0. Furthermore, the influence of the K(+) and Na(+) concentrations and solid-to-liquid ratio on the sorption was very weak, and the values of the thermodynamic parameters revealed that the sorption process was exothermic and spontaneous. All the results suggested that the DMS could be used as an excellent adsorbent to remove U(VI) from aqueous solution.

Immobilized lipase on porous ceramic monoliths for the production of sugar-derived oil gelling agent

Lipase from Candida sp. 99-125 was immobilized on porous ceramic monoliths for the production of sugar-derived oil gelling agent.

A water-dependent kinetics guide for complex lipase-mediated synthesis of biolubricants in a water activity control reactor

A water-dependent kinetic model for a lipase-mediated reaction with multiple substrates and products in a water activity control reactor was developed.

Preparation of robust biocatalyst based on cross-linked enzyme aggregates entrapped in three-dimensionally ordered macroporous silica

With the aim to provide a highly stable and active biocatalyst, cross-linked enzyme aggregates (CLEAs) of lipase Candida sp. 99-125 were prepared in three-dimensionally ordered macroporous silica materials (CLEAs-LP@3DOM-SiO2). Lipase Candida sp. 99-125 was first precipitated in the pores of 3DOM SiO2 (named EAs-LP@3DOM-SiO2), and further cross-linked by glutaraldehyde to form CLEAs-LP@3DOM-SiO2. Saturated ammonium sulfate was used as a precipitant and glutaraldehyde with a concentration of 0.25% (w/w) was employed as a cross-linker. Compared with EAs-LP@3DOM-SiO2 and native lipase, CLEAs-LP@3DOM-SiO2 exhibited excellent thermal and mechanical stability, and could maintain more than 85% of initial activity after 16 days of shaking in organic and aqueous phase. When CLEAs-LP@3DOM-SiO2 was applied in esterification and transesterification reactions, improved activity and reusability were achieved. This method can be used for the immobilization of other enzymes of interest.