Μm Min Research Articles

Room temperature synthesis of defective cerium oxide for efficient marine anti-biofouling

Mimicking marine algae to prevent marine biofouling on the submerged surface of engineering materials represents an alternative and promising approach to conventional toxic anti-biofouling strategy. Here, a novel CeO2 is synthesized by a simple room temperature approach. The as-synthesized CeO2 with rich oxygen vacancies exhibits significantly higher intrinsic haloperoxidase-like activity than the conventional CeO2 in catalyzing the bromination reaction of organic substrates, with a bromination reaction rate of 0.13 µM min−1 at a concentration of 0.05 mg mL−1. In the presence of Br− and H2O2 oxidant, CeO2 demonstrates significant antibacterial efficacies against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, with a significant antibacterial efficiency of 88% and 90%, respectively. Field tests reveal that the plates containing the defective CeO2 (5 wt.%) can effectively hinder the marine biofouling in open ocean. This work provides a promising approach for the development of effective and green marine inorganic anti-foulants at room temperature. Defective CeO2 demonstrates haloperoxidase-like activity towards the catalytic oxidation of bromide, highlighting the potential application towards marine anti-biofouling.

Large-pores anodizing of 5657 aluminum alloy in phosphoric acid: an in-situ electrochemical study

In order to fine tune the morphology of an anodic network, the understanding of the basic electrochemical mechanisms involved is required. The purpose of the present paper is to study the formation of the anodic aluminum oxide (AAO) on 5657 aluminum alloy in H3PO4 when varying the electrolyte concentration (0.1 M – 2 M) and the applied voltage (0–300 V) using a combination of in situ electrochemical investigations and SEM morphological observations.Even if the anodizing voltage and the electrolyte concentration enhance the anodizing rate, the thickness of the anodic film remains limited to 13 µm whatever the electrochemical conditions. The presence of alloying elements induces morphological specificities: the cyclic accumulation/dissolution of the noble elements leads to the formation of regularly spaced transversal pores in the alumina wall. Finally, by selecting appropriate chemical and electrochemical conditions, the fabrication of AAO layer with large and regular pores (until 150 nm of diameter) is possible with a suitable growth rate (0.2 µm min−1 at 90 V in 1 M H3PO4) on the considered commercial complex aluminum alloys.

Synthesis and evaluation of multi-target-directed ligands with BACE-1 inhibitory and Nrf2 agonist activities as potential agents against Alzheimer's disease.

Cumulative evidence suggests that β-amyloid and oxidative stress are closely related with each other and play key roles in the process of Alzheimer's disease (AD). Multitarget regulation of both pathways might represent a promising therapeutic strategy. Here, a series of selenium-containing compounds based on ebselen and verubecestat were designed and synthesized. Biological evaluation showed that 13f exhibited good BACE-1 inhibitory activity (IC50=1.06 μΜ) and potent GPx-like activity (ν0=183.0μMmin-1). Aβ production experiment indicated that 13f could reduce the secretion of Aβ1-40 in HEK APPswe 293T cells. Moreover, 13f exerted a cytoprotective effect against the H2O2 or 6-OHDA caused cell damage via alleviation of intracellular ROS, mitochondrial dysfunction, Ca2+ overload and cell apoptosis. The mechanism studies indicated that 13f exhibited cytoprotective effect by activating the Keap1-Nrf2-ARE pathway and stimulating downstream anti-oxidant protein including HO-1, NQO1, TrxR1, GCLC, and GCLM. In addition, 13f significantly reduced the production of NO and IL-6 induced by LPS in BV2 cells, which confirmed its anti-inflammatory activity as a Nrf2 activator. The BBB permeation assay predicted that 13f was able to cross the BBB. In summary, 13f might be a promising multi-target-directed ligand for the treatment of AD.

Role of grain boundary on the growth behavior of anodic film on spark plasma sintered AA6061

To explore the influence of grain boundary on the growth behavior of anodic film, the grain boundary density of aluminum alloy is adjusted by spark plasma sintering (SPS) with different grain sizes and investigated by techniques including SEM, TEM, and SKP. The results indicated that a suitable grain boundary density effectively uniforms the anodizing current distribution and improves the thickness of the anodic film. In 30 min sulfuric-adipic acid anodizing, the growth rate of the film on the sintering AA6061 reaches 0.47 μm min−1, which is much higher than that of commercial AA6061 under the same conditions. However, excessive grain refinement results in the formation of fine-crystal clusters and a surge of grain boundary density. It enhances field-assistant dissolution in initial anodizing and has a direct weaken effect on the final anodic film thickness.

Therapeutic drug monitoring of intravenous busulfan in Thai children undergoing hematopoietic stem cell transplantation: A pilot study

Busulfan (Bu) is commonly used in myeloablative conditioning regimens for children undergoing hematopoietic stem cell transplantation. The standard target area under the concentration-time curve (AUC) of Bu is approximately 900–1500 µM min. In previous studies using five fixed doses (0.8–1.2 mg/kg) for Bu without dose adjustment, 75% patients achieved the target AUC. The aim of this pilot study was to determine the percentage of target AUC for intravenous (IV) Bu in Thai children. IV Bu was administered every 6 h over 16 doses. Blood samples were collected for pharmacokinetic (PK) analysis after the first, ninth, and thirteenth doses of Bu. Seven patients (2–14 years; median 6 years) were diagnosed with thalassemia (n = 4), acute myeloid leukemia (n = 2), and pure red cell aplasia. Three, two, and two patients received Bu at 1.1, 1.2, and 0.8 mg/kg, respectively. The AUC of Bu varied from 292–1714 µM min (median = 804). Nine (42.86%), eleven (52.38%), and one (4.76%) AUC values were within, below, and above the target, respectively. The median (range) Bu clearance was 5.93 (1.91–14.65) mL/min/kg. In this study, 42.86% AUC value achieved the target, which was lower than that in previous studies. Therapeutic drug monitoring (TDM) of Bu should be considered in Thai children receiving five fixed doses of IV Bu, and dose adjustment should be performed as necessary. Further PK studies for Bu with a larger sample size are warranted for confirming the necessity of TDM in every step dose of Bu. (Trial registration numbers; TCTR20190528003)

Oxygen-functionalized alkyne precursors in carbon nanotube growth

Functionalization of carbon nanotubes (CNTs) with heteroatoms enables covalent attachment, opening up a world of potential material structures. However, common functionalization techniques are hazardous and lack precision. Here, we evaluate an in situ functionalization technique using oxygen-containing alkyne precursors. CNTs were successfully derived from propargyl alcohol and propiolic acid, growing at a rate of 67 ± 7 and 19 ± 3 µm min–1, respectively. While there was no substantial increase in the oxygen content of resultant CNT structures (all less than 1% O), Fourier transform infrared spectroscopy revealed subtle incorporations of carboxyl and hydroxyl functionality. An analysis of reactor effluent showed that both oxygen-containing species shed oxygen groups, where propargyl alcohol yielded a reactive atmosphere high in methylacetylene, and propiolic acid thermally degraded to acetylene and CO2, potentially explaining the enhanced catalyst lifetimes (approximately 75 min). These results support the universality of alkyne-promoting chemistries and delineate the limits of stable, oxygen-bearing alkynes to support point-directed functionalization schemes. Evidence that carbon nanotubes (CNTs) can form from intact C2-C4 subunits, primarily as alkynes, in a polymerization-like growth mechanism opened the doors for functionalized alkynes to direct the placement of heteroatoms in CNT lattice structures. If possible, this would alleviate the need for ex situ functionalization, the costs and environmental burdens associated with high concentration acid processing, and eliminate the random nature currently limiting CNT functionalization. Here, we demonstrate that oxygen-functionalized alkynes dominantly shed their oxygen-containing groups prior to or simultaneously with incorporation in the CNT, resulting in limited incorporation of oxygen groups into the CNT structure. As a whole, the work sheds light on fundamental reaction processes that give rise to carbonaceous nanostructures through polymerization and defines the limits of current in situ functionalization strategies.

Increased activity of alcohol oxidase at high hydrostatic pressure

Alcohol oxidase (AOx) from P. pastoris has potential applications in the production of carbonyl compounds and for the detection and quantification of alcohols. However, AOx’s poor stability and low activity have hindered its practical application. There are two fractions of AOx in P. pastoris with different thermal stability. High hydrostatic pressure (HHP) increased the activity of the labile (L) + resistant (R) combined fractions but not of the R fraction alone. The activity of the L + R fractions increased 2.4-fold at 160 MPa and 30 °C compared to the activity at 0.1 MPa. At higher temperatures, the increase in activity with pressure was greater due to the combined stabilization and activation effects. The reaction rate of the R fraction at 50 °C was 17.9 ± 3.6 or 17.7 ± 0.8 μM min−1 at 80 or 160 MPa, respectively, and was not significantly different from the activity of the L + R fractions under the same conditions (18.4 ± 2.7 μM min-1). The activation energy of the R fraction was not significantly different between 80 MPa (41.5 ± 10.5 kJ mol-1) and 160 MPa (43.8 ± 7.8 kJ mol-1). The combined increase in the stability of the R fraction at HHP enables the use of the enzyme at 50 °C with little loss of activity and an increased catalytic rate.

Mining QTL and genes for root traits and biochemical parameters under vegetative drought in South Indian genotypes of finger millet (Eleusine coracana (L.) Gaertn) by association mapping and in silico comparative genomics

Abstract Finger millet (Elusine coracana) in an important nutria-rich cereal crop. A total of 42 Indian genotypes were used to identify quantitative trait loci (QTL) associated with root traits (root length and root weight) and biochemical parameters (activities of catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), peroxidase (POD), and superoxide dismutase (SOD) enzymes) under drought condition in finger millet. The highest root length (126.40 cm), fresh weight (32.67 gm) and CAT activity (873.13 μM min−1g−1 FW) were observed in TRY-01 genotype under drought condition. Furthermore, the highest APX enzyme activity was observed in GPU-28, INDOF-08, ML-365, THRV-PP, PR-202, and INDOF-07 genotypes. In the present study, five (qtlSSR-06, qtlUGEP-13, qtlUGEP-18, qtlUGEP-104 and qtlUGEP-106) and two (qtlUGEP-07 and qtlUGEP-16) QTL were associated with root length and root weight respectively. Six QTL were associated with biochemical traits such as APX (qtlSSR-06 and qtlUGEP-16), CAT (qtlUGEP-07 and qtlUGEP-16), GR (qtlUGEP-18, qtlUGEP-95, and qtlUGEP-101), SOD (qtlSSR-06 and qtlUGEP-16), and POD (qtlSSR-06 and qtlUGEP-16) activities. An In-silico comparative genomic analysis was performed with genomes of various Poaceae family members to find the QTL associated with any candidate gene. The qtlUGEP-07 was associated with five candidate genes in the different Poaceae family members. Similarly, the qtlUGEP-13 was corresponding to two candidate genes of Panicum hallii. Furthermore, qtlUGEP-16 and qtlUGEP-95 were also associated with candidate genes in foxtail millet and maize. This study will help improve finger millet genotypes under both biotic and abiotic stress conditions.

A Biologically Muscle‐Inspired Polyurethane with Super‐Tough, Thermal Reparable and Self‐Healing Capabilities for Stretchable Electronics

AbstractPolymeric elastomers play an increasingly important role in the development of stretchable electronics. A highly demanded elastic matrix is preferred to own not only excellent mechanical properties, but also additional features like high toughness and fast self‐healing. Here, a polyurethane (DA‐PU) is synthesized with donor and acceptor groups alternately distributed along the main chain to achieve both intra‐chain and inter‐chain donor‐acceptor self‐assembly, which endow the polyurethane with toughness, self‐healing, and, more interestingly, thermal repair, like human muscle. In detail, DA‐PU exhibits an amazing mechanical performance with elongation at break of 1900% and toughness of 175.9 MJ m−3. Moreover, it shows remarkable anti‐fatigue and anti‐stress relaxation properties as manifested by cyclic tensile and stress relaxation tests, respectively. Even in case of large strain deformation or long‐time stretch, it can almost completely restore to original length by thermal repair at 60 °C in 60 s. The self‐healing speed of DA‐PU is gradually enhanced with the increasing temperature, and can be 1.0–6.15 µm min−1 from 60 to 80 °C. At last, a stretchable and self‐healable capacitive sensor is constructed and evaluated to prove that DA‐PU matrix can ensure the stability of electronics even after critical deformation and cut off.

Electrochemical Growth of Mg(OH) x Layered Films Stacked Parallel to the Substrates and Their Thermal Conversion to (111)-Oriented Nanoporous MgO Films.

Stacking layered metal hydroxide films parallel to a substrate is challenging. Here, we demonstrate a simple and rapid electrodeposition method for stacking magnesium hydroxide layered films. Room-temperature cathodic electrolysis (40 mA cm–2) in a Mg(NO3)2 aqueous solution induces the deposition of ⟨001⟩-oriented Mg(OH)x layered films stacked parallel to the substrate at the deposition rate of ∼2 μm min–1. The obtained Mg(OH)x layered films undergo an overall oriented transformation by heat treatment to form ⟨111⟩-oriented nanoporous MgO films.

A novel computer vision-based assessment of neutrophil chemotaxis in patients with severe infection.

ObjectivesTo evaluate the value of chemotactic function of neutrophils in patients with severe infections.MethodsA computer vision‐based cellular chemotaxis analysis platform was established for the dynamic assessment of neutrophil chemotaxis. Fifty‐three patients in the intensive care unit were eligible for the study. In parallel, 142 healthy volunteers were recruited to detect and establish the normal values for chemotactic function. Four chemotactic function indicators were determined–chemotaxis distance (CD), chemotaxis cell ratio (CCR), chemotaxis index (CI) and maximum speed of chemotaxis (Vmax). The chemotaxis function scores (CFS) were calculated for further correlation analysis with clinical data.ResultsThe normal ranges of indicators were established as CD ≥ 1755.85 µm, CCR ≥ 3.34%, CI ≥ 39.63, Vmax ≥ 14.63 µm min−1 and CFS ≥ 15. We found that the chemotactic function of neutrophils in patients suffering from infections was significantly impaired. The mean values of CD, CCR, CI, Vmax and CFS were 1452.8 µm (P < 0.0001), 3.1% (P < 0.0001), 34.5 (P < 0.0001), 12.2 µm min−1 (P < 0.0001) and 9 (P < 0.0001), respectively. CD and CFS were significantly negatively correlated with the APACHE II score (rCD = −0.55, rCFS = −0.39), SOFA score (rCD = −0.68, rCFS = −0.56), procalcitonin concentration (rCD = −0.60, rCFS = −0.5) and the expression of P2RX1 (rCD = −0.76, rCFS = −0.56), respectively.ConclusionsCD, CCR, CI and Vmax can well reflect the neutrophil chemotactic function in patients with severe infections. CFS systematically indicated neutrophil function and has promising clinical application prospects.

Growth of mineralized collagen films by oriented calcium fluoride nanocrystal assembly with enhanced cell proliferation.

Bone is a highly calcified tissue with 60 wt% inorganic components. It is made up of mineralized collagen fibrils, where the platelet-like hydroxyapatite nanocrystals deposit within the collagen fibrils in an oriented manner. Inspired by the special structure and biological activity of bone, we realize the intrafibrillar mineralization of collagen films with oriented calcium fluoride nanocrystals in vitro. Amorphous calcium fluoride (ACF) precursors are generated by polyacrylic acid through polymer-induced liquid precursor processes. The precursors are ready to infiltrate and fill the gap zones laterally and then diffuse to occupy the whole space inside the collagen longitudinally. Finally, the fully mineralized collagen fibrils exhibit a single-crystal-like structure after transforming precursors to co-oriented nanocrystals under the influence of arranged collagen molecules. Expanding the collagen mineralization from 1D fibrils to 2D films, the growth of mineralized areas on the films with a reaction-limited behavior is found. The kinetic rate of growth is around 0.2-0.3 μm min-1, which depends on the pH of the solution. Furthermore, the mineralized collagen films exhibit an enhanced ability of cell proliferation over the pure collagen matrices. Understanding the mineralization of artificial collagen-based scaffolds may have broad promising potentials for bone tissue regeneration and repair in the future.

High-Speed Etching of Silicon Carbide Wafer Using High-Pressure SF6 Plasma

Semiconductor silicon carbide (SiC) is proposed to be a promising material for power-saving devices. However, due to its hard and brittle properties, there is a need to develop a highly efficient strain-free thinning process for the backside thinning of vertical power transistors. As a method for thinning SiC wafers without crystallographic damages, plasma etching with high-pressure SF6 plasma was proposed and the dependence of different processing parameters on the removal rate was investigated. The results revealed that the removal rate was mainly influenced by the power density and relatively insensitive to processing parameters such as processing gap and gas flow rate. It was discovered that a high-speed etching of the entire surface of a commercially available 2-inch wafer at approximately 15 μm min−1 can be achieved by increasing the radio frequency power. Additionally, it was demonstrated that the thickness of the 2-inch wafer can be thinned to approximately 100 μm by only 20 min plasma etching.

L-asparaginase immobilized p(HEMA-GMA) cryogels: A recent study for biochemical, thermodynamic and kinetic parameters

Cryogels have recently been attracted intense attention as suitable carriers for enzyme immobilization. Herein, l-asparaginase was selected as the model enzyme due to its application such as pharmaceutical and food. Under optimum conditions, l-asparaginase was immobilized on poly (2-hydroxyethyl methacrylate-glycidyl methacrylate) cryogels with 68.8% of immobilization yield and 69.3% of activity recovery. The immobilized enzyme exhibited improved stability with respect to the soluble enzyme at extreme conditions, especially around acidic pH and high temperature. Also, the storage stability and reusability of the immobilized enzyme were found to be approximately 54% and 52% of the original activity after 28 days at room temperature and 10 cycles, respectively. The thermodynamic studies indicated that activation energy (Ea) of the free enzyme decreased from 13.08 to 10.97 kJ/mol, which means an increase in the thermostability of l-asparaginase. The Michaelis-Menten constants (Km) of 2.04 and 1.67 mM, and the maximum reaction rates (Vmax) of 170.0 and 115.0 μM min−1 were estimated for soluble and immobilized l-asparaginase, respectively. These findings demonstrated that the designed cryogels turn out to be a good carrier matrix for l-asparaginase immobilization with high catalytic efficiency and enhanced stability.

Dynamics rate of fiber chemical etching: new partial removal of cladding technique for humidity sensing application

Sensor-based optical fibers require thinner cladding for enhanced interaction between the evanescence wave and the environment. Fiber Bragg grated fiber sensors relying on an axial strain require chemical etching to weaken the fiber allowing more sensitivity in terms of strain. Ease of sensor multiplexing can be achieved through etching the mid-section of the fiber which is rarely reported with a custom-made holder. This paper proposes a technique for etching at the middle section of a fiber with a custom fiber holder. Chemical etching of a single-mode silica fiber was done with 48% hydrofluoric acid (HF). Etching proceeds until the fiber was completely etched. The optical spectrum was recorded at an interval of 3 min. Microscope visuals indicated possible etching with the mount design until ∼10 μm at 45 min with the fiber intact compared to a longer etching time. A longer etching duration than 45 min results in the optical spectrum displaying a null spectrum, depicting core damage. Etching of the fiber follows a linear trend and the reaction rate was determined to be 1.699 μm min−1 experimentally. The proposed fiber holder and receptacle were capable of etching a fiber with minimal defects while maintaining the ease of fiber handling.

Bacteria coated cathodes as an in-situ hydrogen evolving platform for microbial electrosynthesis

Hydrogen is a key intermediate element in microbial electrosynthesis as a mediator of the reduction of carbon dioxide (CO2) into added value compounds. In the present work we aimed at studying the biological production of hydrogen in biocathodes operated at − 1.0 V vs. Ag/AgCl, using a highly comparable technology and CO2 as carbon feedstock. Ten bacterial strains were chosen from genera Rhodobacter, Rhodopseudomonas, Rhodocyclus, Desulfovibrio and Sporomusa, all described as hydrogen producing candidates. Monospecific biofilms were formed on carbon cloth cathodes and hydrogen evolution was constantly monitored using a microsensor. Eight over ten bacteria strains showed electroactivity and H2 production rates increased significantly (two to eightfold) compared to abiotic conditions for two of them (Desulfovibrio paquesii and Desulfovibrio desulfuricans). D. paquesii DSM 16681 exhibited the highest production rate (45.6 ± 18.8 µM min−1) compared to abiotic conditions (5.5 ± 0.6 µM min−1), although specific production rates (per 16S rRNA copy) were similar to those obtained for other strains. This study demonstrated that many microorganisms are suspected to participate in net hydrogen production but inherent differences among strains do occur, which are relevant for future developments of resilient biofilm coated cathodes as a stable hydrogen production platform in microbial electrosynthesis.

A Highly Reproducible Micro U-Well Array Plate Facilitating High-Throughput Tumor Spheroid Culture and Drug Assessment.

3D multicellular tumor spheroids (MCTSs) have recently emerged as a landmark for cancer research due to their inherent traits that are physiologically relevant to primary tumor microenvironments. A facile approach–laser‐ablated micro U‐wells–has been widely adopted in the past decade. However, the differentiation of microwell uniformities and the construction of arrays have all remained elusive. Herein, an improved laser‐ablated microwell array technique is proposed that can not only achieve arrayed MCTSs with identical sizes but can also perform high‐throughput drug assessments in situ. Three critical laser ablation parameters, including frequency, duty cycle, and pulse number, are investigated to generate microwells flexibly with a range from 170 to 400 μm. The choice of microwells is optimally arranged into an array via precise control of horizontal spacing (d x) and vertical spacing (d y) amenable of cell‐loss‐free culture during cell seeding. Harvested T24, A549 and Huh‐7 MCTSs from the microwell array correspond to approximately 75 to 140 μm in diameter. Anticancer drug screening of cisplatin validated IC50 values in 2D and MCTS conditions are 3.5 versus 9.1 μM (T24), 11.8 versus 277.7 μM (A549) and 33.5 versus 52.8 μM (Huh‐7), and the permeability is measured to range from 0.042 to 0.58 μm min−1.

Fabrication of ultra-high-aspect-ratio nano-walls and nano-structures on silicon substrates

Realization of high-aspect-ratio vertical features on silicon substrates is a crucial step in the fabrication process of microelectromechanical systems devices. Therefore deep reactive ion etching (DRIE) plays an important role in the fabrication of those structures. Recently many efforts have been made in order to propose the novel DRIE processes in order to achieve higher aspect ratios; however, they suffer from complexity and high sensitivity to process parameters. Herein, the authors report a high-aspect-ratio vertical etching of silicon by employment of proposed low temperature SiO2 deposition on Si substrate, using of H2 and O2 gases. The process employs multiple sequences of alternating steps of etching by a fluorine donating gas such as SF6 and sidewall passivation by SiO2. Etch rates reach up to 0.8 μm min−1 and values of aspect ratio higher than 100 are readily achievable by this process. Furthermore, this process also allows for controlled fabrication of nano-wall and high-aspect-ratio nano-wall tube as well as three-dimensional silicon structures.

Intravitreal Bevacizumab for Macular Edema Secondary to Retinal Vein Occlusion.

The most common cause of vision loss in cases of Retinal vein occlusion (RVO) is due to macular edema. This study was conducted to examine the effect of intravitreal bevacizumab (IVB) in the treatment of macular edema secondary to RVO. The authors conducted a retrospective study of 94 eyes (N) of 92 patients with macular edema associated with decreased visual acuity secondary to RVO who were treated with IVB. Patients received IVB at baseline, 1 month and 2 months. At each follow up patients were evaluated and re-injected if necessary. The mean age of the patients was 56.6 ±11.51 years. The average number of injections per eye was 2.1 ± 0.87. The baseline median central macular thickness (CMT) and best-corrected visual acuity (BCVA) in LogMAR was 465.00μm (Min 254μm, Max 1218μm) and 1.00 (Min 0.30, Max 2.28), respectively. The median CMT at one month following first, second and third dose of IVB was 258μm (N=94, Z= -7.64, p <0.001), 261μm (N=63, Z= -0.17, p=0.86), and 292μm (N=41, Z= -0.21, p= 0.83), respectively. The median LogMAR BCVA at one month following first, second and third dose of IVB was 0.60 (N=94, Z= -5.70, p < 0.001), 0.60 (N=63, Z= -1.69, p=0.09), and 0.60 (N=41, Z= -0.03, p=0.97), respectively. Pre-operative BCVA was the best predictor of the final visual outcome after IVB in cases of RVO. None of the patients developed any serious ocular or systemic complications due to IVB. IVB is an effective and safe treatment for macular edema associated with decreased visual acuity secondary to RVO. The most beneficial effect of IVB is seen at one month after the first dose. The efficacy of subsequent doses could not be established in this study.

Purification and Characterization of Mannanase from Aspergillus awamori for Fruit Juice Clarification.

Fruit juice clarification is a challenging aspect of beverage industry which needs to be addressed for economical and hygienic production of fruit juices. Current study is focused on the complete purification, characterization and thermodynamic analysis of an efficient mannanase enzyme to analyze its applicability in biological clarification fruit juice. Mannanase production using Aspergillus awamori IIB037 in a 25 L stirred fermenter at pre optimized reaction conditions was carried out. Enzyme purification was carried out via series of steps. Characterization of enzyme along with kinetics and thermodynamic studies was conducted. Purified and characterized enzyme was assessed for its applicability in fruit juice clarification through clarification experiments on fresh apple juice. Purification fold of 3.98 was obtained along with 86.80% purification yield of mannanase with specific activity of 158.16 U/mg. The molecular size of purified enzyme was determined as 66 kDa. The enzyme depicted 56% residual activity at 60°C after 8 hrs. Thermodynamic studies of an enzyme revealed enthalpy of activation (ΔH) and activation energy (Ea) as 30.53KJ/mol, 27.76KJ/mol, respectively. The enzyme activity increased in the presence of ß-mercaptoethanol surprisingly. On the other hand, methyl alcohol, ethanol, Hg2+ and Cu2+ inhibited enzyme activity. The enzyme showed Km and Vmax values of 11.07 mM and 19.08 μM min-1 for Locust Bean Gum (LBG) under optimal conditions. Juice treated with mannanase showed decrease in absorbance and increase in reducing sugar content. The current study demonstrated that mannanase from Aspergillus awamori in its purified form has significant characteristics to be employed industrially for juice clarification.