The catalytic activity of laccase immobilized onto free and surfactant modified silica aerogels

The free silica aerogel (FSA) and surfactant (cetyltrimethylammonium bromide) modified silica aerogel (MSA) were synthesized and used as supports for laccase immobilization carried out through adsorption process. The results show that the MSA performed higher laccase adsorption (0.71µmol/g) as compare to FSA (0.22µmol/g). In addition, the enhancement of the catalytic activity of the MSAL was also observed. These results demonstrated that the surface modification of silica aerogel using cationic surfactant (cetyltrimethylammonium bromide) gave higher immobilized mass and catalytic activity of laccase which can be potentially used for degradation of organic micropollutants such dyes, pesticides and antibiotics

Influence of Avocado Purée as a Fat Replacer on Nutritional, Fatty Acid, and Organoleptic Properties of Low-Fat Muffins

Objective: The feasibility of developing reduced-fat muffins with avocado is investigated by preparing muffins with 25%, 50%, 75%, and 100% avocado pur�ee as a fat (butter) replacer. Methodology: The resulting products were compared to the control muffin, which was made with 100% butter. Muffins were analyzed for nutritional content, fatty acid profiles, and sensory acceptability. Result: Muffins incorporated with avocado pur�ee revealed a significant increase (p < 0.05) with respect to moisture, ash, and carbohydrate in comparison with the control sample. However, no significant changes (p > 0.05) were detected in all muffin formulations for protein and dietary fiber content. Both fat content and caloric value of muffins incorporated with avocado pur�ee were significantly decreased (p < 0.05). The fatty acid profile showed that there was an increment in the monounsaturated fatty acids (MUFA) content by 16.51% at full-fat substitution. The sensory evaluation test demonstrated that muffins had acceptability at up to 50% substitution. Fat substitution at higher than 50% lead to undesirable flavor and aftertaste, which was significant (p < 0.05) to the panelists. Conclusion: The findings indicated the feasibility of avocado pur�ee in fat-reduced muffin preparation with an optimal level of 50% avocado pur�ee substitution

Characterization of natural zeolite for adsorptive removal of antibiotics from aqueous solution

The persistent existence of antibiotics in sewage wastewater treatment plants in recent years has emerged as a serious concern. In this study, natural zeolite (NZ02) obtained from China was employed as an adsorbent to remove tetracycline (TC) from aqueous solution. The characterization results show that the NZ02 consists of quartz, clinoptilolite-Na and heulandite having the CEC of 62.18cmol/kg and the surface area of 36.646m2/g. Adsorption results show that the maximum adsorption capacity of TC on NZ02 was 19.30mg/g and the equilibrium data followed theLangmuir adsorption isotherm model

Natural zeolite characterization for adsorptive coagulation flocculation (ACF) removal of ammonium in drinking water treatment process

The naturally occurring zeolite (N Z01) was characterized and used as an adsorbent for the removal of ammonium (N-NH4+) from water. The characterization results show that the NZ01 is mainly composed of clinoptilolite, quartz and plagioclase and has the cation-exchange capacity (CEC) of 64 cmol/kg. Batch adsorption results show that the best ammonia removal was at pH close to that of the natural water (= pH 7). The increase in initial ammonium nitrogen concentration from 5 to 50 ppm resulted in an increase of the adsorption capacity from 0.64 to 15.1 mg NH4+-N/g. The Jar test experiments indicate the introduction of the NZ01 enhanced the ammonium removal efficiency. All these results demonstrate that the NZ01 is potential to be used for the removal of ammonium in drinking water treatm ent process

Removal of dyes by silica nanoparticles with immobilized laccase

Dyes give a big impact on ecosystem; thus several methods have been developed for dye removal processes. This study investigated the dye removal by the combination of adsorption and biodegradation process. Silica nanoparticles (SN), modified silica nanoparticle (MSN), silica nanoparticle with laccase (SNL), and modified silica nanoparticle with laccase (MSNL) were synthesized. All samples were characterized with scanning electron microscope (SEM), nitrogen adsorption-desorption (NAD), Fourier transform infrared (FTIR), and energy dispersive X-ray (EDX). It was found that the introduction of cationic surfactant and laccase did not change the morphology but it affected the surface area, pore characteristics and chemical properties of the SN. The dye adsorption performance using SN and MSN was evaluated in batch adsorption experiment at various experimental conditions. The adsorption of methylene blue (MB) by SN showed a good adsorption performance (qe = 0.2291 mmol/g) as compared to the MSN (qe = 0.0430 mmol/g). In contrast, for methyl orange (MO), the MSN showed a very good adsorption performance (qe = 0.1849 mmol/g), while no adsorption was observed for the SN. The pH values did not give any significant effect on the dye adsorption and the cetyltrimethylammonium bromide (CTAB) concentration of 1mM was found to be the maximum value for SN modification. The adsorption equilibrium and kinetic data for both MO and MB fit the Temkin and Langmuir isotherm models well, respectively while the kinetic adsorption data follows the Elovich kinetic model with film diffusion found to be the rate-limiting step. The dye adsorption process was found to be exothermic, spontaneous and physisorption. The regeneration shows that SN and MSN are reusable for multiple cycles. For the laccase immobilization, MSN performed higher laccase adsorption (1.6696 µmol/g) as compared to SN (1.1047 µmol/g). The removal of dye by SNL and MSNL was analyzed in term of adsorption and degradation of both MO and MB dyes. Results show that the removal of MB by SNL was higher (qe = 0.2573 mmol/g) than SN (qe = 0.2291 mmol/g). Meanwhile, removal of MO by MSNL was higher (qe = 0.2454 mmol/g) as compared to MSN (qe = 0.1849 mmol/g). These results demonstrated that the surface modification of SN by cationic surfactant gave higher catalytic activity of laccase, hence giving higher removal performance of dye. The adsorption isotherm data analysis shows that the SNL and MSNL are well fitted to the Langmuir and Temkin model respectively. The Elovich kinetic model is however the best model to describe the dye adsorption kinetic data of both SNL and MSNL. The dye removal by degradation was analyzed using Michaelis-Menten enzymatic reaction equation which found that higher specific activity was observed for MSNL (88.5724 U/g) as compared to SNL (22.6360 U/g). This resulted in higher initial enzymatic reaction velocity, Vmax (58.0 µM/min) for MO (MSNL) and lower for MB (SNL) (58.0 µM/min)

Parent-report instruments for assessing feeding difficulties in children with neurological impairments: a systematic review

AIM This study aimed to review the psychometric properties and clinical application of parent-report instruments that assess feeding difficulties in children with neurological impairments. METHOD Papers were identified through five electronic databases based on 15 keywords and were included if they met the following criteria: published in English, described the implementation of parent-report instruments, and included children with neurological impairments (either in the report or a related study population). RESULTS In total, 1220 relevant abstracts were screened and 22 full-text articles were evaluated. The following six parent-report instruments met the inclusion criteria: (1) Screening Tool of Feeding Problems applied to children, (2) Paediatric Eating Assessment Tool, (3) Paediatric Assessment Scale for Severe Feeding Problems, (4) Montreal Children’s Hospital Feeding Scale, (5) Children’s Eating Behaviour Inventory, and (6) Behavioural Paediatric Feeding Assessment Scale (BPFAS). Based on comprehensive psychometric testing and consistently good results, the BPFAS was considered the most valid and reliable instrument. The BPFAS also showed good clinical applicability because it was readily available, required a short administration time, and used a simple scoring system. INTERPRETATION We reviewed the available parent-report instruments for assessing feeding difficulties in children with neurological impairments. The BPFAS had the best psychometric properties and clinical applicability

Effect of synthesis conditions on physical properties, laccase catalytic activity and stability of sol-gel laccase

The physical properties, laccase catalytic activity and stability of sol–gel laccases prepared at various synthesis conditions were investigated. The sol–gel laccases were characterized using the scanning electron microscope (SEM), Fourier transform infrared spectrophotometer and nitrogen adsorption/desorption analyzer. The laccase catalytic activity of the synthesized sol–gel laccases was determined by using 2,6-dimethoxyphenol as a standard substrate. The SEM results confirmed that the sol–gel laccases have a spherical agglomerated particle morphology having surface area and pore properties varied with synthesis conditions. It was found that the laccase catalytic activity and stability of sol–gel laccases were enhanced depending on synthesis conditions used. There was no significant laccase leaching observed, suggesting that most of the laccase molecules were sterically confined in the silica matrices. The highest laccase catalytic activity was observed for the SOLAC04 (480 AU) which also had the highest surface area (445 m2/g), pore size (30.7 nm) and pore volume (1.14 cm3/g). The optimal conditions for the laccase loading were 10 mg/mL, pH for both free laccase and SOLAC04 was 6, and temperature for the free laccase and SOLAC04 was 50 and 40 °C, respectively. The laccase catalytic activity of SOLAC04 could retain almost 90 % of its original activity after 34-day storage duration at 27 °C. These results demonstrated the advantages offered by the sol–gel laccases

Preparation and characterization of in situ entrapment of laccase in silica microparticles via an ambient drying procedure

A simple and reproducible method for in situ entrapment of laccase in silica microparticles was studied which involved hydrolysis and condensation of tetraethyl orthosilicate via sol–gel route using one-step (base catalyst) and two-step (acid–base catalyst) methods followed by an ambient drying procedure. The influence of method used, starting material compositions, and aging conditions toward polymeric structure and catalytic activity of the laccase entrapped silica microparticles (LSMs) were investigated. It was found that one-step method is not suitable for in situ entrapment purpose since it left significant amount of untrapped laccase in the reaction media and lead to laccase inactivation due to its active site alteration by continuous contact with basic condition. Conversely, the laccase was entirely entrapped in the silica matrices synthesized using the two-step method with the highest specific activity of 434.71 U/g obtained for the immobilized laccase. In addition, the LSM showed stability improvement toward pH and temperature compared to the free laccase and was able to retain more than 80 % of their initial catalytic activity after 1 month of storage duration. The treatment of the LSM with trimethylchlorosilane resulted in the increase in the surface hydrophobic properties which is expected to be useful for applications in nonaqueous medium

Synthesis and characterization of immobilized white-rot fungus Trametes versicolor in sol–gel ceramics

Trametes versicolor (TV) cells were embedded in ceramic matrices (TV Biocers) through sol–gel method using tetraethyl orthosilicate as a silica precursor. The characterization of the free silica and TV Biocers was carried out by using scanning electron microscope, transmission electron microscope, Fourier transform infrared spectrophotometer, nitrogen adsorption–desorption measurement and catalytic activity assay. The performance of the TV Biocers as biocatalysts was evaluated using methylene blue (MB) and malachite green (MG) dyes as model emerging organic micropollutants. It was observed that the dye removal performance η (mmol g−1) of the TV Biocers for MB and MG, respectively, was 7.400 and 5.569 mmol g−1 which was 18 and 128 % higher than the TV Biocers calculated values obtained from the free silica and free TV cells. These results demonstrated that the TV Biocers can offer better dye removal performance through a combination of adsorption and degradation processes. This is the first reported study on the immobilization of the TV cells in silica matrices, and further study is underway to improve their properties toward its applications for removal of emerging organic micropollutants. Graphical abstract: [Figure not available: see fulltext.

Antimicrobial effect of Malaysian vegetables against enteric bacteria

Objective: To investigate the antibacterial activities of green vegetables (pennywort, mint, garlic, parsley and celery) against four common enteric bacteria [Salmonella enterica (ATCC 25957) (S. enterica), Shigella flexneri (ATCC 12022) (S. flexneri), Escherichia coli (ATCC 43889) (E. coli) and Enterobacter cloacae (ATCC 13047) (E. cloacae)] as an alternative medicine for controlling food borne diarrhea disease and the synergistic effect of green vegetables against those bacteria. Methods: Five common vegetables (pennywort, mint, garlic, parsley and celery) were purchased and extracted. The antimicrobial activities of these extracts were tested against four common enteric bacteria (S. enterica, S. flexneri, E. coli and E. cloacae). Ten different concentrations of the extracts (from 640 to 1.25 mg/mL) were prepared and used for the study. The minimal inhibitory concentration (MIC) was determined by the broth dilution method. The antimicrobial activities were assessed by using both well diffusion and disc diffusion methods. Results: Garlic extract showed excellent inhibitory effects on all enteric bacteria. Other plants (parsley, celery, mint and pennywort) were not effective against enteric bacteria. The MIC of garlic against S. flexneri and E. cloacae was 40 mg/mL. The MIC of S. enterica and E. coli were 20 and 10 mg/mL, respectively. The performance of the well diffusion method was better than that of the disc diffusion method with clear and sharp inhibition zones of tested bacteria against plant extracts. Conclusions: Garlic had excellent antimicrobial effects against enteric bacteria and was recommended to be given to patients with gastroenteritis. The other vegetables (pennywort, mint, parsley and celery) showed no inhibitory effects on enteric bacteria but still can be used for its richness in vitamins and fibers. The performance of the well diffusion method was better than that of the disc diffusion method in detecting the antibacterial effects of green vegetables