Percentage Of Hydrolysis Research Articles

Impact of Nanoscale Magnetite and Zero Valent Iron on the Batch-Wise Anaerobic Co-Digestion of Food Waste and Waste-Activated Sludge

As a potential approach for enhanced energy generation from anaerobic digestion, iron-based conductive nanoparticles have been proposed to enhance the methane production yield and rate. In this study, the impact of two different types of iron nanoparticles, namely the nano-zero-valent-iron particles (NZVIs) and magnetite (Fe3O4) nanoparticles (NPs) was investigated, using batch test under mesophilic conditions (35 °C). Magnetite NPs have been applied in doses of 25, 50 and 80 mg/L, corresponding to 13.1, 26.2 and 41.9 mg magnetite NPs/gTS of substrate, respectively. The results reveal that supplementing anaerobic batches with magnetite NPs at a dose of 25 mg/L induces an insignificant effect on hydrolysis and methane production. However, incubation with 50 and 80 mg/L magnetite NPs have instigated comparable positive impact with hydrolysis percentages reaching approximately 95% compared to 63% attained in control batches, in addition to a 50% enhancement in methane production yield. A biodegradability percentage of 94% was achieved with magnetite NP doses of 50 and 80 mg/L, compared to only 62.7% obtained with control incubation. NZVIs were applied in doses of 20, 40 and 60 mg/L, corresponding to 10.8, 21.5 and 32.2 mg NZVIs/gTS of substrate, respectively. The results have shown that supplementing anaerobic batches with NZVIs revealed insignificant impact, most probably due to the agglomeration of NZVI particles and consequently the reduction in available surface area, making the applied doses insufficient for measurable effect.

Recovery and identification bioactive peptides from protein isolate of Spirulina platensis and their in vitro effectiveness against oxidative stress-induced erythrocyte hemolysis.

Spirulina platensis is recognized as one of the most nutritious foods, containing a high protein content of up to 70%. Meanwhile, he interest in using natural protein resources to develop bioactive peptides is steadily increasing. Therefore, this study released the bioactive peptides from S. platensis by enzymatic hydrolysis using pepsin (1:3000 U g-1 ), and their amino acid sequences were determined by de novo sequencing. On this basis, the antioxidant activities of synthesized bioactive peptides were comprehensively evaluated by 2,2'-azinobis-3-ethylbenzothiazolin-6-sulfonic acid assay, 1,1-diphenyl-2-picryhydrazyl assay, and cell hemolysis assay induced by 2,2'-azobis-(2-amidino-propane) dihydrochloride (AAPH). The degree of hydrolysis and recovery percentage of pepsin hydrolysis were 172 and 825 g kg-1 respectively, and FFEFF (P1: m/z 736.4, 8%), EYFDALA (P2: m/z 828.4, relative intensity 18.5%), and VTAPAASVAL (P3: m/z 899.5, relative intensity 17.3%) were purified and identified. P2 possessed an excellent radical scavenging activity compared with P1, P3, and vitamin C, which was contributed to by its high β-sheet conformation and specific amino acid compositions. Moreover, P2 significantly attenuated AAPH-induced oxidative hemolysis of erythrocytes and protected the erythrocytes, because it reduced the formation of malondialdehyde and increased the enzyme activities of superoxide dismutase, catalase, and glutathione peroxidase in erythrocytes. This study provided insights into the potential antioxidant function of the synthesized peptides originated from the bioactive peptides of S. platensis proteins, which would contribute to the development of natural antioxidant from new protein resources. © 2020 Society of Chemical Industry.

Potential beneficial effect of hydrothermal treatment of starches from various sources on in vitro digestion

Starches from various botanic origins (maize, quinoa, wheat, potato and rice) were studied. The thermal and pasting properties and their connection with enzyme digestibility were evaluated. Various hydrothermal treatments were applied, taking the starch physical parameters into account, in order to obtain partial and total gelatinisation of the starch structure and determine its influence on enzymatic action. Onset and pasting temperatures of the gelatinisation and pasting processes, respectively, followed the same order in the cereal starches (rice > maize > wheat > quinoa). These results were accompanied by an opposite trend in the percentage of raw starch hydrolysis, with quinoa reaching a level more than 2-fold higher than that of raw maize starch in in vitro digestion kinetics. Other technological parameters, such as high peak viscosity or low breakdown, also reflected modifications in the quinoa starch structure which were related to improved digestibility. However, starch from potato, the only tuber, displayed different characteristics from those of cereal starch, showing greater resistance to digestion. When the starches were pretreated, digestibility increased in all of them compared to their raw counterparts, with the pretreated quinoa and wheat starches showing greater susceptibility to modification of their structure. Although the hydrothermally pretreated maize and rice starches reached about 75% of the hydrolysis index of the corresponding gelatinised starches, raw quinoa had a similar hydrolysis index and quinoa obtained a higher value for total starch hydrolysed. Thus, quinoa starch could be potentially beneficial in the design of more digestible formulations for patients with metabolic disorders such as glycogen storage disease, among others.

Cowpea storage under nitrogen‐modified atmosphere at different temperatures: Impact on grain structure, cooking quality, in vitro starch digestibility, and phenolic extractability

Cowpeas were stored for 12 months under a nitrogen-modified atmosphere at 15, 20, and 25°C. Cowpeas analyzed immediately, without subjection to the storage period, constituted the initial sample. Long-term storage promoted changes in the cooking characteristics of the cowpeas as a result of a rigidized cotyledon structure. Hardened cowpeas exhibited lower percentages of starch hydrolysis. Even under nitrogen-modified storage, the higher temperatures of 20 and 25°C favored the structural alterations that hampered the enzymatic digestion of starch. The changes were minimal at 15°C, indicating that the combination of a nitrogen-modified atmosphere and the indicated temperature not only most accurately maintained the coat color, but also provided the best glucose release results. The storage period and the cooking procedure reduced the free phenolic and proanthocyanidin content of the cowpeas, regardless of the applied storage conditions. Increases in the extractability of bound phenolics were observed, regardless of the storage conditions. Practical applications Results of the present study contribute to the understanding of the effects of the storage conditions on the cooking and nutritional quality of cowpeas and may help the cowpea production chain to adopt proper technologies in order to guarantee a constant supply of high-quality cowpeas to consumers from the developed and developing countries. The color, physicochemical properties, and starch digestibility were considered in the determination of the quality of stored cowpeas.

Biohydrogen production from organic solid waste in a sequencing batch reactor: An optimization of the hydraulic and solids retention time

Hydrogen production from organic solids waste was evaluated using a sequencing batch reactor (SBR) under mesophilic conditions, to investigate the effect of the hydraulic retention time (HRT) and solids retention time (SRT) on hydrogen production. The examined HRT and SRT values were from 4.6 to 27 h and 17–102 h, respectively. The results showed high hydrogen production rates (1.86 LH2/L·d) and a yield of 127.26 mLH2/gCODremoved for an SRT of 60 h and an HRT of 16 h. The highest chemical oxygen demand (COD) removal (38.6 ± 6.9%) was also obtained under those conditions. The highest substrate hydrolysis percentage (73.0 ± 11.4%) was obtained at an HRT of 16 h and an SRT of 102 h. A short SRT of 20 h affected hydrogen production, which decreased up to 90%. With an SRT of 20 h and an HRT of 16 h, acetic acid-like fatty acids were mainly obtained. In experiments with a long SRT (60 h), the obtained fatty acid was butyrate. The conversion efficiencies for converting particulate material into fatty acids were 51–47% using a long SRT; a short HRT resulted in percentages of 37–40%. A 3D surface analysis was performed using the maximum hydrogen yield conditions as the central point, showing that the optimal hydrogen production can be obtained with an HRT of 16 h and an SRT of 55 h. Microbial analysis showed the predominance of the Olsenella genus at an HRT< 8 h and the presence of Clostridium at an HRT of 16 h. The HRT is the main parameter leading the community composition in the process.

Quinoa starch nanocrystals production by acid hydrolysis: Kinetics and properties

Quinoa starch (QS) acid hydrolysis was investigated, focusing on the kinetics and physicochemical properties of nanocrystals production as a function of temperature (30, 35 and 40 °C). Waxy maize starch (WMS) was hydrolyzed at 40 °C for comparison. QS presented different hydrolysis percentages at 30 °C (63%), 35 °C (73%) and 40 °C (91%), on the fifth day. QS showed faster hydrolysis (first-order rate constant, k = 0.59 day−1) than WMS (k = 0.39 day−1) at 40 °C. Material produced at 30 °C was micrometric-sized and irregularly-shaped while that at 35 and 40 °C, was nanometric-sized and conical and parallelepiped-shaped. The hydrolysis temperature increase did not affect the crystallinity index of quinoa starch nanocrystals (QSNC), whereas zeta potential and Fourier transform infrared spectroscopy band intensities increased, and thermal transition peak temperature and thermal stability decreased when hydrolysis temperature increased. QSNC were produced at 35 and 40 °C with yields of 22.8% and 6.8%, respectively. At 40 °C, QSNC presented smaller sizes than WMS nanocrystals, but also lower yield and crystallinity index.

Economic production of thermo-active endo β-mannanase for the removal of food stain and production of antioxidant manno-oligosaccharides

β-Mannanases are β-1,4-mannan-glycosidic bonds hydrolyzing enzymes that participate in various biotechnological applications. In the current study, the production of the enzyme was performed by solid state fermentation of rice straw using the locally isolated fungus Trichoderma longibrachiatum RS1 and the production of the enzyme was optimized to reach 89.73U/g dry substrate. The isolated fungus was identified on the base of its cultural and morphological features and by 18S rDNA sequencing.The optimum temperature for the activity of the partially purified enzyme was indicated to be 75 °C. Although production of fungal β-mannanases have been previously studied but the production of thermo-active enzymes are still challengeable. The Vmax and Km were 6.2U/mg protein/min and 3.33 mg/mL respectively, indicating the comparatively high affinity of the produced enzyme toward mannan substrates. The thermal stability of the produced enzyme estimated that its half lives were 633.01, 50.77 and 20.25 min−1 at 55, 60 and 65 °C respectively. The produced enzyme can be efficiently used in the removal of mannan based food stain. Moreover, the efficiency of the produced enzyme in the production of manno-oligosaccharides by the hydrolysis of mannan polymers was examined. The results indicated the release of 1.8 and 0.66 mg reducing sugar/mL by the hydrolysis of locust bean and guar gum for 2 h with hydrolysis percentage of 27 and 9.9% respectively. Finally, the produced manno-oligosaccharides were examined for their antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl free radical.

Cationic starch and polyacrylamides for alkenyl succinic anhydride (ASA) emulsification for sizing of cellulosic fibers

Paper is composed of polysaccharides mainly cellulose and carbohydrates. The hydroxyl groups present in cellulose react with various substances added to fibrous slurry. Treating the cellulosic fibers chemically, which tends to develop the resistance to aqueous liquid absorption, is known as internal sizing of paper. The main internal alkaline sizing chemicals are alkyl ketene dimer and alkenyl succinic anhydride (ASA). In situ emulsification of ASA using cationic starch (CS) is conventionally practiced because of the low shelf life of ASA emulsion. In the present communication polyacrylamides (PAMs) have been used as an alternative chemical to cationic starch at very low dosages than cationic starch and varying ratios of ASA to polyacrylamides to stabilize the ASA droplets. The colloidal stability of ASA emulsions was measured in terms of particle size distribution, sizing performance, pH and percent hydrolysis of ASA with the passage of time. The ASA emulsions prepared with PAMs at very low dosage were observed with superior colloidal stability and sizing behaviour than the CS stabilized emulsion.

Biobutanol production from sulfuric acid-pretreated red algal biomass by a newly isolated Clostridium sp. strain WK.

Marine biomass, especially the algal biomass, is currently considered to be one of the most potential candidates for biofuels conversion during the development of biomass utilization. In this study, a diluted sulfuric acid pretreatment method was established for biobutanol from red algal biomass Gelidium amansii using a newly isolated Clostridium sp. strain WK. Under the optimal condition of 2% sulfuric acid treated in 20Min at 131°C, the maximal hydrolysis percentage of biomass can reach up to 80.95%, and the biobutanol production was obtained to be 3.46g/L with a yield of 0.20g/g after the fermentation of biomass hydrolysate. This result demonstrated a 12.5-fold enhancement of conversion efficiency compared with the untreated control, which provides a new and efficient way to develop the biobutanol industry by utilizing the abundant, low cost, and carbohydrate-rich algal biomass.

Understanding the mechanism of ultrasonication regulated the digestibility properties of retrograded starch following vacuum freeze drying

The digestibility properties and structural changes of retrograded starch (RS3) induced by ultrasonic treatment (UT) were investigated. The digestion profiles showed that UT increased the slowly digestible starch (SDS) or resistant starch (RS) of RS3 as an effective green process, corresponding to a change in hydrolysis kinetic parameters (equilibrium starch hydrolysis percentage and kinetic constant). SEM analysis showed that ultrasound led to breakage of RS3 particles followed by cracking, reorientation and crystallization. Differences in amylose content, granule size, and ζ-potential were found for native RS3 and ultrasound-treated RS3 (UT-RS3). UT decreased the relative crystallinity and gelatinization enthalpy but enhanced short-range order of RS3 based on the results of XRD, DSC, and FT-IR, respectively. Surprisingly, diffractive peaks at 13°and 20° (V-type crystalline structure) and a new exothermic peak were also observed for UT-RS3. The outcome was believed to open new pathways for regulating the digestibility properties of RS3 by UT and development of low glycemic response food.

Increasing Temperature and Microplastic Fibers Jointly Influence Soil Aggregation by Saprobic Fungi.

Microplastic pollution and increasing temperature have potential to influence soil quality; yet little is known about their effects on soil aggregation, a key determinant of soil quality. Given the importance of fungi for soil aggregation, we investigated the impacts of increasing temperature and microplastic fibers on aggregation by carrying out a soil incubation experiment in which we inoculated soil individually with 5 specific strains of soil saprobic fungi. Our treatments were temperature (ambient temperature of 25°C or temperature increased by 3°C, abruptly versus gradually) and microplastic fibers (control and 0.4% w/w). We evaluated the percentage of water stable aggregates (WSA) and hydrolysis of fluorescein diacetate (FDA) as an indicator of fungal biomass. Microplastic fiber addition was the main factor influencing the WSA, decreasing the percentage of WSA except in soil incubated with strain RLCS 01, and mitigated the effects of temperature or even caused more pronounced decrease in WSA under increasing temperature. We also observed clear differences between temperature change patterns. Our study shows that the interactive effects of warming and microplastic fibers are important to consider when evaluating effects of global change on soil aggregation and potentially other soil processes.

Characterization of a Mixture of Oca (Oxalis tuberosa) and Oat Extrudate Flours: Antioxidant and Physicochemical Attributes

The oca (Oxalis tuberosa) is a tuber with high starch content and excellent antioxidant properties, which can be used in the production of extruded products; however, starch-rich products can be improved nutritionally through the incorporation of fibers that can result in extrudates with beneficial health properties. The aim of this work was to develop a mixture of oca (Oxalis tuberosa) and oat extrudate flours and evaluate the antioxidant and physicochemical attributes. The results showed that a higher moisture content increased the hardness, water absorption index, and density of the extrudates; however, the solubility and expansion indexes showed an inverse pattern. The addition of oat fiber had the opposite effect from moisture content on the physicochemical properties mentioned above. The cellular antioxidant activity (CAA) of the extrudates decreased when the oat fiber increased. An inverse pattern was observed when the moisture concentration was increased. The starch hydrolysis percentage and glycemic index decreased significantly when the fiber content increased. Oat fiber contributed 67.29% and 65.04% to these parameters, respectively. Oat fiber exerted a greater effect than moisture on the collets extruded in this study according to factor contributions.

Co-immobilization of multiple enzymes onto surface-functionalized magnetic nanoparticle for the simultaneous hydrolysis of multiple substrates containing industrial wastes

The present study focused on the co-immobilization of multi-enzymes onto magnetic nanoparticles (MNPs) and surface-functionalized MNPs for the hydrolysis of fish processing solid waste (FPSW) containing complex molecules. The MNPs were synthesized and surface-functionalized by chemical (cMNP and SF-cMNP) and biological method [biologically synthesized iron oxide magnetic nanoparticle (bIOMNP)] and was characterized by various instrumental analyses. Lipase and protease produced from Streptomyces thermolineatus were co-immobilized onto the synthesized bare and surface-functionalized MNPs. At the optimum conditions, the lipase and protease loading capacity of cMNP were found as 1000 and 783 U/g, respectively, whereas the lipase and protease loading capacity of SF-cMNP were 2920 and 2350 U/g, respectively, and bIOMNP was 2800 and 2196 U/g, respectively. The thermal, pH and storage stabilities of the co-immobilized enzymes were greatly enhanced compared to the free enzymes and the Vmax and Km of the free and co-immobilized enzymes were also determined. The free and the co-immobilized enzymes were used for the hydrolysis of lipids and proteins in FPSW. The percentage hydrolysis of lipids and proteins in FPSW was 52.8 and 61.8%, respectively, for LP-cMNP, 76.2 and 84.1%, respectively, for LP-SF-cMNP and 73.9 and 82.1%, respectively, for LP-bIOMNP.

Comparison between microwave‐cooking and steam‐cooking on starch properties and in vitro starch digestibility of cooked pigmented rice

AbstractThe influence of two types of cooking method, that is, steam‐cooking and microwave‐cooking, on the morphological structure, starch fractions, and starch digestibility of cooked Thai pigmented rice (three cultivars) was examined. The relationship between starch hydrolysis and change in X‐ray diffraction (XRD) pattern, including the change of crystallinity degree during in vitro digestion, was also investigated. The results indicated that the cooked rice morphological structure and starch hydrolysis rate during in vitro digestion was varied by the cooking method. All non‐waxy rice cultivars exhibited Vh‐type crystallinity, whereas, no crystalline peak was detected in the waxy rice cultivar. However, the XRD pattern and crystallinity degree of steam‐cooked rice were dramatically changed after simulated small intestinal digestion for 360 and 480 min when compared with microwave‐cooked rice. Moreover, steam‐cooked rice showed a significantly lower percentage of equilibrium starch hydrolysis than that of the microwave‐cooked rice.Practical applicationsRice attributes and change of crystallinity in XRD pattern during in vitro digestion have found to correlate with rice starch digestibility, which varied depending on rice cooking methods. Steam‐cooking could enhance the degree of crystallinity during in vitro digestion, which would affect to retard rice starch digestion. This finding is interesting for the consumer on the selection of the optimized cooking process that promotes a healthier effect.

In Vitro Bioaccessibility of Low-Crystallinity Phytosterol Nanoparticles Generated Using Nanoporous Starch Bioaerogels.

Phytosterols are natural health-promoting bioactive compounds; however, phytosterols have very limited bioavailability due to their crystalline lipophilic structure. With the aim of improving bioaccessibility, low-crystallinity phytosterol nanoparticles were generated by supercritical carbon dioxide (SC-CO2 ) impregnation of phytosterols into nanoporous starch aerogels (NSAs). The in vitro bioaccessibility of the phytosterol nanoparticles (35%) was significantly higher than that of the crude phytosterols (3%) after sequential oral, gastric, and intestinal digestion. The percentages of starch hydrolysis were not different among the various NSA preparations and reached to 64% after sequential digestion. The zeta potential of the phytosterol nanoparticles was higher compared to that of crude phytosterols in the micellar phase; indicating higher stability. The findings of this study support the use of NSA to produce nanoparticles of reduced crystallinity to improve the bioaccessibility of the lipophilic bioactive compounds. PRACTICAL APPLICATIONS: This novel process can decrease the size and crystallinity of phytosterols and thus improve phytosterols' bioavailability. It is a blueprint to apply to other water insoluble food bioactives. This novel approach may (i) improve the health benefits of water-insoluble bioactives; (ii) enable food manufacturers to add water-insoluble bioactives into low- and high-fat foods to produce health-promoting foods; and (iii) enhance the cost-benefit ratio of water insoluble bioactives.

Optimization of free fatty acid production by enzymatic hydrolysis of vegetable oils using a non-commercial lipase from Geotrichum candidum.

This study aimed to optimize free fatty acid production by enzymatic hydrolysis of cottonseed, olive and palm kernel oils in stirred-tank reactors using a lipase from Geotrichum candidum (GCL-I). The effect of pH, temperature and substrate concentration on the hydrolytic activity of GCL-I using these vegetable oils was investigated. Thermal stability tests and thermodynamic studies were also performed. A complete hydrolysis of cottonseed oil was obtained after 120min of reaction, while for olive and palm kernel maximum hydrolysis percentage was 96.4% and 60.1%, respectively. GCL-I exhibited the highest activity in the hydrolysis of vegetable oils that are rich in unsaturated-fatty acids (cottonseed and olive oils). Under optimal conditions (46.8% m/m of oil, 6.6 U/g of the reaction mixture at 40°C), complete cottonseed oil hydrolysis was observed at 60min of reaction performed in an emulsifier-free system with no buffer.

Kluyveromyces lactis β-galactosidase immobilized on collagen: catalytic stability on batch and packed-bed reactor hydrolysis

The aim of this study was to evaluate the catalytic characteristics and operational stability of the tetrameric Kluyveromyces lactis β-galactosidase (KLG) enzyme immobilized on collagen. The support was submitted to four different treatments: aluminum, glutaraldehyde, acetic acid, and a combination of the methods with aluminum and glutaraldehyde. The four modified supports and the enzyme, both in its soluble and immobilized forms, were studied using thermogravimetric, differential exploratory calorimetry, infrared spectroscopy, and textural analyses. Operational pH, temperature and kinetic parameters of the soluble enzyme and of derivatives were characterized. Immobilized enzyme was applied in milk and whey lactose hydrolysis, via batch and continuous processing. There was no significant reduction (p < 0.05) in immobilization yields of all derivatives with loads up to 100 mgprotein/gsupport, with yields of approximately 70%. All derivatives reached a percentage of approximately 50% of lactose hydrolysis after 17 reuse cycles in the hydrolysis of milk and whey, using batch processing. On the other hand, hydrolysis percentages higher than 50% were achieved with packed-bed reactor even after 48 h of operation. Immobilized KLG on collagen maintained its catalytic characteristics and showed good operational stability in hydrolysis processes, especially in the continuous processes with packed-bed reactor.

Co-production of microbial lipids and biosurfactant from waste office paper hydrolysate using a novel strain Bacillus velezensis ASN1

Microbial lipids and biosurfactant were successfully co-produced using waste office paper (WOP) as a substrate using a novel strain Bacillus velezensis ASN1. WOP was pretreated with 1% (v/v) H2SO4 and enzymatically hydrolyzed using cellulase (37 FPU/g solid) and β-glucosidase (25 CBU/g solid). The total sugar yield was 21.28 g/L at 120 h and the percentage of hydrolysis was 89.07%. The obtained WOP hydrolysate was used as a substrate for the co-production of microbial lipids and biosurfactant. The best nitrogen source and carbon to nitrogen ratio for lipid production was found to be ammonium chloride and C/N 20, respectively. A lipid content of 31% was obtained with a fatty acid profile of myristic, pentadecanoic, palmitic, and stearic acid methyl esters. The crude biosurfactant was extracted by acid precipitation of the supernatant yielded 0.818 g/L and was characterized using NMR, FTIR, and LC–MS, and proved as lipopeptides. The biorefinery approach of co-producing of microbial lipid and biosurfactant using waste paper would reduce the production cost of biodiesel.

Commercial and non-commercial pectinase and cellulase on the enzymatic hydrolysis efficacy of rice husk and Tifton 85 hay

The aim of this study was to evaluate the action of commercial and non-commercial cellulase and pectinase on rice husk and Tifton 85 hay hydrolyses. The hydrolysis kinetics of the substrates with commercial cellulase and pectinase were evaluated and the hydrolysis at different temperature and agitation conditions was maximized using experimental design. The combined use of commercial and non-commercial enzymes under optimized conditions was evaluated. The pre-treatment of the residues was also investigated by milling and different concentrations of NaOH. Finally, the effect of the hydrolysis on the bromatological composition of the residues was evaluated. The best hydrolysis times of rice husk and Tifton 85 hay were 10 and 12h for commercial cellulase, 12 and 14h for non-commercial cellulase, 10 and 14h for commercial pectinase and 16 and 20h for non-commercial pectinase, respectively. The highest hydrolysis values were obtained using commercial cellulase with 1:50 (w:v enzyme:water) dilution rate, at 45ºC and 300 rpm agitation for both substrates, reaching 20.6% maximum percentage for Tifton 85 hay and 11.6% for rice husk. The combined use of commercial enzymes did not increase hydrolysis percentage. The pre-treatment using 7.5% NaOH and 0.5 mm grain size significantly increased the rice husk and Tifton 85 hay hydrolyses (60-80%), either using commercial cellulase or pectinase enzymes. The use of non-commercial enzymes provided 18-30% hydrolysis obtained from commercial ones. Bromatological analyzes indicated a reduction in neutral detergent fiber and acid detergent fiber content for rice husk and Tifton 85 hay when using pectinases and commercial cellulases.

Feasibility of aluminum recovery and MgAl2O4 spinel synthesis from secondary aluminum dross

The feasibility of aluminum recovery from secondary aluminum dross by extraction with NaOH solution and the subsequent synthesis of MgAl2O4 spinel by sintering the extracted slag were studied. The extraction percentage of soluble aluminum from the dross reached 80% at a temperature of 353 K, liquid-to-solid ratio of 12 mL·g−1, stirring speed of 300 r·min−1, and an extraction time of 15 min; the hydrolysis percentage of AlN reached 40% with an extraction time of 30 min. The activation energies of the soluble aluminum and AlN extracted from the dross were 7.15 and 8.98 kJ·mol−1, respectively, indicating that their kinetics were controlled by outer diffusion without a product layer. The extracted slag was sintered in the temperature range 1373–1773 K; MgAl2O4 spinel with a compressive strength as high as 69.4 MPa was produced in the sample sintered at 1673 K for 3 h. This value exceeds the threshold (40 MPa) prescribed by the National Standard for the Magnesia and Magnesia−alumina Refractory Bricks of China (GB/T 2275–2007). These results establish the effectiveness of aluminum recovery from secondary aluminum dross and subsequent MgAl2O4 spinel synthesis.