Immobilization of indigenous holocellulase on iron oxide (Fe 2 O 3 ) nanoparticles enhanced hydrolysis of alkali pretreated paddy straw

Immobilization and Characterization of a Processive Endoglucanase EG5C-1 from Bacillus subtilis on Melamine-Glutaraldehyde Dendrimer-Functionalized Magnetic Nanoparticles

Exploring an appropriate immobilization approach to enhance catalytic activity and reusability of cellulase is of great importance to reduce the price of enzymes and promote the industrialization of cellulose-derived biochemicals. In this study, Fe3O4 magnetic nanoparticles (MNPs) were functionalized with meso-2,3-dimercaptosuccinic acid to introduce carboxyl groups on the surface (DMNPs). Then, melamine-glutaraldehyde dendrimer-like polymers were grafted on DMNPs to increase protein binding sites for the immobilization of processive endoglucanase EG5C-1. Moreover, this dendrimer-like structure was beneficial to protect the conformation of EG5C-1 and facilitate the interaction between substrate and active center. The loading capacity of the functionalized copolymers (MG-DMNPs) for EG5C-1 was about 195 mg/g, where more than 90% of the activity was recovered. Immobilized EG5C-1 exhibited improved thermal stability and increased tolerability over a broad pH range compared with the free one. Additionally, MG-DMNP/EG5C-1 biocomposite maintained approximately 80% of its initial hydrolysis productivity after five cycles of usage using filter paper as the substrate. Our results provided a promising approach for the functionalization of MNPs, enabling the immobilization of cellulases with a high loading capacity and excellent activity recovery.

Cellulase immobilization to enhance enzymatic hydrolysis of lignocellulosic biomass: An all-inclusive review

Cellulase-mediated lignocellulosic biorefinery plays a crucial role in the production of high-value biofuels and chemicals, with enzymatic hydrolysis being an essential component. The advent of cellulase immobilization has revolutionized this process, significantly enhancing the efficiency, stability, and reusability of cellulase enzymes. This review offers a thorough analysis of the fundamental principles underlying immobilization, encompassing various immobilization approaches such as physical adsorption, covalent binding, entrapment, and cross-linking. Furthermore, it explores a diverse range of carrier materials, including inorganic, organic, and hybrid/composite materials. The review also focuses on emerging approaches like multi-enzyme co-immobilization, oriented immobilization, immobilized enzyme microreactors, and enzyme engineering for immobilization. Additionally, it delves into novel carrier technologies like 3D printing carriers, stimuli-responsive carriers, artificial cellulosomes, and biomimetic carriers. Moreover, the review addresses recent obstacles in cellulase immobilization, including molecular-level immobilization mechanism, diffusion limitations, loss of cellulase activity, cellulase leaching, and considerations of cost-effectiveness and scalability. The knowledge derived from this review is anticipated to catalyze the evolution of more efficient and sustainable biocatalytic systems for lignocellulosic biomass conversion, representing the current state-of-the-art in cellulase immobilization techniques.

Facile pretreatment strategies to biotransform Kans grass into nanocatalyst, cellulolytic enzymes, and fermentable sugars towards sustainable biorefinery applications

The present investigation is targeted towards the facile fabrication of a carbon-based nanocatalyst (CNCs) using Kans grass biomass (KGB) and its sustainable application in microbial cellulase enhancement for the alleviation of enzymatic hydrolysis for sugar production. Different pretreatments, including physical, KGB extract-mediated treatment, followed by KOH pretreatment, have been applied to produce CNCs using KGB. The presence of CNCs influences the pretreatment of KGB substrate, fungal cellulase production, stability, and sugar recovery in the enzymatic hydrolysis of KGB. Using 1.0% CNCs pretreated KGB-based solid-state fermentation, 33 U/gds FPA and 126 U/gds BGL were obtained at 72 h, followed by 107 U/gds EG at 48 h in the presence of 0.5% CNCs. Further, 42 °C has been identified as the optimum temperature for cellulase production, while the enzyme showed thermal stability at 50 °C up to 20 h and produced 38.4 g/L sugar in 24 h through enzymatic hydrolysis of KGB.

Cellulase Immobilization on Nanostructured Supports for Biomass Waste Processing

Nanobiocatalysts, i.e., enzymes immobilized on nanostructured supports, received considerable attention because they are potential remedies to overcome shortcomings of traditional biocatalysts, such as low efficiency of mass transfer, instability during catalytic reactions, and possible deactivation. In this short review, we will analyze major aspects of immobilization of cellulase-an enzyme for cellulosic biomass waste processing-on nanostructured supports. Such supports provide high surface areas, increased enzyme loading, and a beneficial environment to enhance cellulase performance and its stability, leading to nanobiocatalysts for obtaining biofuels and value-added chemicals. Here, we will discuss such nanostructured supports as carbon nanotubes, polymer nanoparticles (NPs), nanohydrogels, nanofibers, silica NPs, hierarchical porous materials, magnetic NPs and their nanohybrids, based on publications of the last five years. The use of magnetic NPs is especially favorable due to easy separation and the nanobiocatalyst recovery for a repeated use. This review will discuss methods for cellulase immobilization, morphology of nanostructured supports, multienzyme systems as well as factors influencing the enzyme activity to achieve the highest conversion of cellulosic biowaste into fermentable sugars. We believe this review will allow for an enhanced understanding of such nanobiocatalysts and processes, allowing for the best solutions to major problems of sustainable biorefinery.

Facile Cellulase Immobilisation on Bioinspired Silica

Cellulases are enzymes with great potential for converting biomass to biofuels for sustainable energy. However, their commercial use is limited by their costs and low reusability. Therefore, the scientific and industrial sectors are focusing on finding better strategies to reuse enzymes and improve their performance. In this work, cellulase from Aspergillus niger was immobilised through in situ entrapment and adsorption on bio-inspired silica (BIS) supports. To the best of our knowledge, this green effect strategy has never been applied for cellulase into BIS. In situ entrapment was performed during support synthesis, applying a one-pot approach at mild conditions (room temperature, pH 7, and water solvent), while adsorption was performed after support formation. The loading efficiency was investigated on different immobilisation systems by Bradford assay and FTIR. Bovine serum albumin (BSA) was chosen as a control to optimize cellulase loading. The residual activity of cellulase was analysed by the dinitro salicylic acid (DNS) method. Activity of 90% was observed for the entrapped enzyme, while activity of ~55% was observed for the adsorbed enzyme. Moreover, the supported enzyme systems were recycled five times to evaluate their reuse potential. The thermal and pH stability tests suggested that both entrapment and adsorption strategies can increase enzyme activity. The results highlight that the entrapment in BIS is a potentially useful strategy to easily immobilise enzymes, while preserving their stability and recycle potential.

Metal-organic framework promoting high-solids enzymatic hydrolysis of untreated corncob residues

Metal-organic frameworks (MOFs) could serve as efficient matrixes to immobilize cellulase because of their high stability and porous morphology. Herein, the Zr-based MOFs (UiO-66 and UiO-66-NH₂) assisted 20 wt% high-solids hydrolysis of untreated corncob residues (CRs) at low enzyme loading was investigated. Glucan hydrolysis yields increased to 60.55% and 71.47% by separately adding 4 g/L UiO-66 and UiO-66-NH₂ at 5 FPU/g-glucan cellulase dosage. The maximum hydrolysis yield reached 90.01% at 10 FPU/g-glucan in the presence of 4 g/L UiO-66-NH₂. Analysis of free protein concentration and cellulase activity suggested that MOFs effectively increased cellulase catalytic activity and stability, thus boosted CRs enzymatic hydrolysis efficiency. Additionally, UiO-66-NH₂ immobilization gave a high catalytic activity because of the abundant anchor sites of NH₂ groups. This research presents the promising future of MOFs' application in lignocellulosic biomass bioconversion and other areas requiring immobilized enzymes.

A SiO2 Microcarrier with an Opal-like Structure for Cross-Linked Enzyme Immobilization

The opal-like SiO₂ microcarriers with different pore diameters named opal-SiO₂I and opal-SiO₂II were synthesized and utilized as microcarriers to immobilize Rhizopus oryzae lipase (ROL) and Aspergillus oryzae α-amylases (AOA). ROL and AOA can be more stably immobilized on the cross-linked SiO₂ opals by neopentyl glycol diglycidyl ether (NGDE), which is the first attempt to use it as a cross-linking agent compared with glutaraldehyde. According to the morphology analysis, multiple layers of SiO₂ monodisperse microspheres were regularly packed and formed an opal-like structure, and enzymes were well scattered and immobilized throughout the SiO₂ opals. The results showed that the performance of enzymes immobilized on opal-SiO₂II with a larger specific surface area was much better than that of opal-SiO₂I. The enzyme activity of ROL@opal-SiO₂II and AOA@opal-SiO₂II cross-linked with 1% NGDE increased 5.32 and 9.32 times compared with their free counterpart, respectively. Furthermore, pH and thermal stability and reusability of ROL/AOA@opal-SiO₂II were significantly improved and higher than those of ROL/AOA@opal-SiO₂I and free enzymes. This study provides an easily obtained microcarrier opal-SiO₂II, which shows potential for efficient different enzyme immobilizations and further industrial applications.

Biogenic enabled in-vitro synthesis of nickel cobaltite nanoparticle and its application in single stage hybrid biohydrogen production

In biomass to biofuels production technology enzyme plays a key role. Nevertheless, the high production cost of cellulase enzyme is one of the critical issues in the economical production of biofuels. Nowadays, implementation of nanomaterials as catalyst is emerging as an innovative approach for the production of sustainable energy. In this context, synthesis of nickel cobaltite nanoparticles (NiCo₂O₄ NPs) via in vitro route has been conducted using fungus Emericella variecolor NS3 meanwhile; its impact has been evaluated on improved thermal and pH stability of crude cellulase enzyme obtained from Emericella variecolor NS3. Additionally, bioconversion of alkali treated rice straw using NiCo₂O₄ NPs stabilized cellulase produced sugar hydrolyzate which is further used for H₂ production via hybrid fermentation. Total 51.7 g/L sugar hydrolyzate produced 2978 mL/L cumulative H₂ production after 336 h along with maximum rate 34.12 mL/L/h in 24 h using Bacillus subtilis PF_1 and Rhodobacter sp. employed for dark and photo-fermentation, respectively.

Cellulases: From Bioactivity to a Variety of Industrial Applications

Utilization of microbial enzymes has been widely reported for centuries, but the commercial use of enzymes has been recently adopted. Particularly, cellulases have been utilized in various commercial sectors including agriculture, brewing, laundry, pulp and paper and textile industry. Cellulases of microbial origin have shown their potential application in various commercial sectors including textile, pulp and paper, laundry, brewing, agriculture and biofuel. Cellulases have diversified applications in the food industry, food service, food supply and its preservation. Indeed, cellulases can tenderize fruits, clarify the fruit juices, reduce roughage in dough, hydrolyze the roasted coffee, extract tea polyphenols and essential oils from olives and can increase aroma and taste in food items. However, their role in food industries has by and large remained neglected. The use of immobilized cellulases has further expanded their application in fruit and vegetable processing as it potentiates the catalytic power and reduces the cost of process. Technological and scientific developments will further expand their potential usage in the food industry.

Preparation of regenerable magnetic nanoparticles for cellulase immobilization: Improvement of enzymatic activity and stability

To obtain regenerable magnetic nanoparticles, triethoxy(3-isocyanatopropyl)silane and iminodiacetic acid (IZ) were used as the starting material and immobilized on Fe₃ O₄ nanoparticles. Copper ions (Cu²⁺ ions) were loaded on the Fe-IZ nanoparticles and used for cellulase immobilization. The support was characterized by spectroscopic methods (FTIR, NMR) and thermogravimetric analysis, transmission electron microscopy, scanning electron microscope, X-ray diffraction, energy dispersive X-ray analysis, and vibrating sample magnetometer techniques. As a result of experiments, the amount of protein bound to immobilized cellulase (Fe-IZ-Cu-E) and cellulase activity was found to be 33.1 mg/g and 154 U/g at pH 5, 50°C, for 3 h. The results indicated that the free cellulase had kept only 50% of its activity after 2 h, while the Fe-IZ-Cu-E was observed to be around 77%, at 60°C. It was found that the immobilized cellulase maintained 93% of its initial catalytic activity after its sixth use. Furthermore, the Fe-IZ-Cu-E retained about 75% of its initial activity after 28 days of storage. To reuse the support material (Fe-IZ-Cu), it was regenerated by thorough washing with ammonia or imidazole.

Impact of nanoparticle inclusion on bioethanol production process kinetic and inhibitor profile

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NiO nanoparticle (NP) inclusion enhanced bioethanol production up to 59.96 %.

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Band energy gap impact NP catalytic performance in bioethanol production.

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NiO nanoparticle biocatalyst improved bioethanol productivity by 145 %.

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Modified Gompertz model was used to describe ethanol production with NP inclusion.

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Metallic NiO nanoparticles significantly reduced acetic acid concentration by 110 %.

This study examines the effects of nanoparticle inclusion in instantaneous saccharification and fermentation (NIISF) of waste potato peels. The effect of nanoparticle inclusion on the fermentation process was investigated at different stages which were: pre-treatment, liquefaction, saccharification and fermentation. Inclusion of NiO NPs at the pre-treatment stage gave a 1.60-fold increase and 2.10-fold reduction in bioethanol and acetic acid concentration respectively. Kinetic data on the bioethanol production fit the modified Gompertz model (R ² > 0.98). The lowest production lag time (t _L) of 1.56 h, and highest potential bioethanol concentration (P _m) of 32 g/L were achieved with NiO NPs inclusion at different process stages; the liquefaction stage and the pre-treatment phase, respectively. Elevated bioethanol yield, coupled with substantial reduction in process inhibitors in the NIISF processes, demonstrated the significance of point of nanobiocatalysts inclusion for the scale-up development of bioethanol production from potato peels.

Recent Advances of Cellulase Immobilization onto Magnetic Nanoparticles: An Update Review

Cellulosic enzymes, including cellulase, play an important role in biotechnological processes in the fields of food, cosmetics, detergents, pulp, paper, and related industries. Low thermal and storage stability of cellulase, presence of impurities, enzyme leakage, and reusability pose great challenges in all these processes. These challenges can be overcome via enzyme immobilization methods. In recent years, cellulase immobilization onto nanomaterials became the focus of research attention owing to the surface features of these materials. However, the application of these nanomaterials is limited due to the efficacy of their recovery process. The application of magnetic nanoparticles (MNPs) was suggested as a solution to this problem since they can be easily removed from the reaction mixture by applying an external magnet. Recently, MNPs were extensively employed for enzyme immobilization owing to their low toxicity and various practical advantages. In the present review, recent advances in cellulase immobilization onto functionalized MNPs is summarized. Finally, we discuss enhanced enzyme reusability, activity, and stability, as well as improved enzyme recovery. Enzyme immobilization techniques offer promising potential for industrial applications.

Immobilization of cellulase on a core-shell structured metal-organic framework composites: Better inhibitors tolerance and easier recycling

For the first time, cellulase was successfully immobilized on a magnetic core-shell metal-organic framework (MOF) material, UIO-66-NH₂. The as-prepared immobilized cellulase demonstrated a high protein loading efficiency of 126.2 g/g support and a high enzyme activity recovery of 78.4%. Cellulase immobilized on magnetic UIO-66-NH₂ exhibited a superior performance in terms of pH stability, thermal stability and catalytic efficiency compared to its free form. Notably, immobilized cellulase could be recycled for up to 5 consecutive runs. Furthermore, compared to free cellulase, immobilized cellulase showed better tolerance to formic acid and vanillin, two typical inhibitors found in lignocellulosic prehydrolysates. In the presence of 5 g/L of formic acid and vanillin, immobilized cellulase demonstrated 16.8% and 21.5% higher activity than free enzyme, respectively, and its improvement in hydrolysis yield was 18.7% and 19.6% respectively. This is firstly confirmed that immobilization can alleviate the inhibitory effects of certain pretreatment inhibitors on cellulase.