Thermostability of crude endoglucanase from Aspergillus fumigatus grown under solid state fermentation (SSF) and submerged fermentation (SmF)

Sequential cultivation method for β-fructofuranosidase production from Aspergillus tamarii URM4634, evaluation of their biochemical and kinetic/thermodynamic characteristics, and application on sucrose hydrolysis

The present study focused on evaluating the sequential fermentation (SF) method for FFase production from Aspergillus tamarii URM4634 using soybean bran as substrate. The SF was performed using soybean bran as substrate at 72 h and 30 °C and the maximum hydrolytic activity (44.00 U mL-1), corresponding to an increase of 2.98-fold to about SmF using sucrose as substrate. Already the maximum transfructosylating activity was 26.10 U mL-1. The FFase presents maximum hydrolytic activity at pH 5.0-6.0 and transfructosylating at pH 6.0 and 60 °C for both enzyme activities. The enzyme showed a typical hydrolytic kinetic profile evidenced by more affinity by sucrose hydrolysis reaction than the fructosyl transfer one. From kinetic and thermodynamic data of thermal denaturation, it was observed that the enzyme presents suitable at 55 °C, evidenced by the large half-life (990.21 min) and D values (3289.41 min). The maximum release of reducing sugars (8.45 g L-1) was obtained in hydrolysis of 20% sucrose during 180 min. The results obtained for FFase production by SF proved that this method can be used satisfactorily for sucrose-degrading enzymes and can contribute to the development of the SF technique to produce different industrial-interest enzymes.

Enhanced fermentation and deconstruction of natural wheat straw by Trichoderma asperellum T-1 and its positive transcriptional response

Microorganisms harvest energy from agricultural waste by degrading its structure. By comparing with Trichoderma reesei QM6a in cellulase production, straw deconstruction and transcriptome response, Trichoderma asperellum T-1 was identified to be prioritized for the fermentation of natural straw. Cellulase activity of T-1 was 50%-102% higher than QM6a. And the degradation rate of hemicellulose and ligin in wheat straw by T-1 reached 40% and 42%. Time-driven changes in the gene expression of extracellular proteins involved in polysaccharide, xylan, and hemicellulose metabolism and hydrolysis indicated that T-1 positively responded in both solid state fermentation and submerged fermentation for lignocellulose degradation. A significantly enriched category encoding carbohydrate-binding modules is considered critical for the deconstruction of the natural structure by T-1. The findings highlight the superiority of T. asperellum T-1 in straw fermentation, base on which, the construction of efficient microbial agents is expected to enhance the utilization of biomass.

Biochemical and thermodynamic properties of de novo synthesized urease from Vicia sativa seeds with enhanced industrial applications

Urease is one of the most significant enzymes in the industry. The objective of this research was to isolate and partially purify urease from Vicia sativa seeds with urease characterization. With a 6.4 % yield, the purification fold was 9.0. By using chromatography, it was determined that the isolated urease had a molecular weight of 55 kDa. The maximum urease activity was found following a 60-s incubation period at 40 °C and pH 8. The activity of urease was significantly boosted by a mean of calcium, barium, DL-dithiothreitol, Na2EDTA, and citrate (16.9, 26.6, 18.6, 13.6, and 31 %), respectively. But nickel and mercury caused inhibitory effects and completely inhibited urease activity, indicating the presence of a thiol (-SH) group in the enzyme active site. The Arrhenius plot was used to analyze the thermodynamic constants of activation, Ea, ΔH*, ΔG*, and ΔS*. The results showed that the values were 30 kJ/mol, 93.14 kJ/mol, 107.17 kJ/mol/K, and -40.80 J/mol/K, respectively. The significance of urease extraction from various sources may contribute to our understanding of the metabolism of urea in plants. The current report has novelty as it explained for the first time the kinetics and thermodynamics of hydrolysis of urea and inactivation of urease from V. sativa seeds.

Synthesis of dietary lipids from pumpkin (Cucurbita pepo. L) oil obtained by enzymatic extraction: a sustainable approach

This study aimed to assess the nutritional properties of dietary lipids obtained through the modification of aqueous enzymatically extracted pumpkin seed (Cucurbita pepo. L) oil. The optimal growth conditions for producing pectinase using strain Aspergillus sp. 391 were determined, and partial characterization of pectinase and commercial cellulase was conducted. The enzymatic extraction was performed at pH 4.0, 50 °C, for 24 h, using a combination of pectinase and cellulase for optimum effectiveness. The crude oil obtained was analyzed for acid, peroxide, and fatty acid composition. The study found a high amount of unsaturated fatty acids, mainly linoleic acid (C18:2), and a 59% oil recovery rate. Subsequently, this oil was subjected to enzymatic acidolysis with capric acid in solvent-free media, catalyzed by lipase Lipozyme RM IM®, resulting in a product with a higher incorporation degree (48.39 ± 0.5 mol%), observed after 24 h at 60 °C using molar ratio oil:acid capric of 1:9 (run 4). The nutritional properties of this oil were improved.

Optimization strategy for inulinase production by Aspergillus niger URM5741 and its biochemical characterization, kinetic/thermodynamic study, and application on inulin and sucrose hydrolysis

Inulinases are enzymes of great interest in the food industry, especially due to their application in the synthesis of fructose and fructo-oligosaccharides. Moreover, some inulinases (I) also present invertase activity (S), making them useful for sucrose hydrolysis processes. In the present study, the production of inulinase by Aspergillus niger URM5741 was evaluated and optimized using two statistical approaches. First, the composition of the cultivation medium was determined through a simplex centroid mixture design, followed by the selection of optimal fermentation conditions using the Box-Behnken design. Based on these experimental designs, the maximum activities of inulinase (16.68 U mL-1) and invertase (27.80 U mL-1) were achieved using a mixture of wheat, soy, and oat brans (5 g), along with 2.5% inulin and 40% moisture. The inulinase exhibited optimum temperature and pH of 60 °C and 4.0, respectively, displayed a high affinity for both substrates, as evidenced by very-low Michaelis constant values (1.07-1.54 mM). A relative thermostability was observed at 55-60 °C as indicated by half-lives values (I: 169.06-137.27 min; S: 173.29-141.52 min) and D-values (I: 561.61-456.00 min; S: 575.65-470.11 min) which were further confirmed by the high activation energy (123.01 and 143.29 kJ mol-1). The enzyme demonstrated favorable results in terms of inulin and sucrose hydrolysis, being a maximum release of reducing sugars of 6.04 and 15.80 g L-1, respectively. These results indicate that the sequential statistical approach proved to be beneficial to produce inulinase by A. niger URM5741, with the obtained enzyme considered promising for long-term industrial applications.

Recovery of agricultural waste biomass: A path for circular bioeconomy

Circular bio-economy is a significant approach to resolving global issues elevated by environmental pollution. The generation of bioenergy and biomaterials can withstand the energy-environment connection as well as substitute petroleum-based materials as the feed stock production, thereby contributing to a cleaner and low-carbon-safe environment. Open discarding of waste is a major cause of environmental pollution in developing and under developed countries. Agricultural bio-wastes are obtained through various biological sources and industrial processing, signifying a typical renewable source of energy with ample nutrients and readily biodegradable organic substances. These waste materials are competent to decompose under aerobic and anaerobic conditions. The projected global population, urbanization, economic development, and changing production and consumption behavior result in bounteous bio-waste production. These bio-wastes mainly contain starch, cellulose, protein, hemicellulose, and lipids, which can operate as low-cost raw materials to develop new value-added products. Thus, this review discussed specifically the agricultural waste and valorization processes used to convert this waste into value-added products (biofuel, enzymes, antibiotics, ethanol and single cell protein). These value added products are used in the supply chain and enhance the overall performance of agriculture waste management, execution of circular bio-economy has attained significant importance and it explains a closed-loop system in which the potential resources remain in the loop, allowing them to be sustained into a new value.

Purification and thermodynamic characterization of acid protease with novel properties from Melilotus indicus leaves

A thermostable acid protease from M. indicus leaves was purified 10-fold using a 4-step protocol. We were able to isolate a purified protease fraction with a molecular weight of 50 kDa and exhibited maximal protease activity at pH 4.0 and 40 °C. Structural analysis revealed that the protease is monomeric and non-glycosylated. The addition of epoxy monocarboxylic acid, iodoacetic acid, and dimethyl sulfoxide significantly reduced protease activity while dramatically increasing the inhibition of Mn²⁺, Fe²⁺, and Cu²⁺. The activation energy of the hydrolysis reaction (33.33 kJ mol^-1) and activation energy (E_d = 105 kJ mol^-1), the standard enthalpy variation of reversible protease unfolding (2.58 kJ/mol) were calculated after activity measurements at various temperatures. Thermal inactivation of the pure enzyme followed first-order kinetics. The half-life (t_1/2) of the pure enzyme at 50 °C, 60 °C, and 70 °C was 385, 231, and 154 min, respectively. Thermodynamic parameters (entropy and enthalpy) suggested that the protease was highly thermostable. This is the first report on the thermodynamic parameters of proteases produced by M. indicus. The novel protease appears to be particularly thermostable and may be important for industrial applications based on these thermodynamic properties.

Purification and enzymatic properties of a new thermostable endoglucanase from Aspergillus oryzae HML366

Aspergillus oryzae HML366 is a newly screened cellulase-producing strain. The endoglucanase HML ED1 from A. oryzae HML366 was quickly purified by a two-step method that combines ammonium sulfate precipitation and strong anion exchange column. SDS-PAGE electrophoresis indicated that the molecular weight of the enzyme was 68 kDa. The optimum temperature of the purified endoglucanase was 60 ℃ and the enzyme activity was stable below 70 ℃. The optimum pH was 6.5, and the enzyme activity was stable at pH between 4.5 and 9.0. The analysis indicated that additional Na⁺, K⁺, Ca²⁺, and Zn²⁺ reduced the catalytic ability of enzyme to the substrate, but Mn²⁺ enhanced its catalytic ability to the substrate.The Km and Vmax of the purified endoglucanase were 8.75 mg/mL and 60.24 μmol/min·mg, respectively. In this study, we report for the first time that A. oryzae HML366 can produce a heat-resistant and wide pH tolerant endoglucanase HML ED1, which has potential industrial application value in bioethanol, paper, food, textile, detergent, and pharmaceutical industries.

A Combined Study on Optimization, In Silico Modeling, and Genetic Modification of Large Scale Microbial Cellulase Production

Cellulase is a biocatalyst that hydrolyzes cellulosic biomass and is considered a major group of industrial enzymes for its applications. Extensive work has been done on microbial cellulase but fungi are considered a novel strain for their maximum cellulase production. Production cost and novel microbial strains are major challenges for its improvement where cheap agro wastes can be essential sources of cellulose as substrates. The researcher searches for more cellulolytic microbes from natural sources but the production level of isolated strains is comparatively low. So genetic modification or mutation can be employed for large-scale cellulase production before optimization. After genetic modification than in silico molecular modeling can be evaluated for substrate molecule's binding affinity. In this review, we focus not only on the conventional methods of cellulase production but also on modern biotechnological approaches applied to cellulase production by a sequential study on common cellulase-producing microbes, modified microbes, culture media, carbon sources, substrate pretreatment process, and the importance of optimum pH and temperature on fermentation. In this review, we also compare different cellulase activity determination methods. As a result, this review provides insights into the interrelationship between the characteristics of optimizing different culture conditions, genetic modification, and in silico enzyme modeling for the production of cellulase enzymes, which may aid in the advancement of large-scale integrated enzyme manufacturing of substrate-specific enzymes.

Simultaneous Production and Immobilization of Lipase Using Pomegranate-Seed Residue: A New Biocatalyst for Hydrolysis Reactions and Structured Lipids Synthesis

Pomegranate-seed residue (PSR) was used in a new strategy for the simultaneous production of Yarrowia lipolytica lipase by submerged fermentation and its immobilization by adsorption. This biocatalyst—the fermented solid residue containing the adsorbed lipase (fermPSR)—was evaluated in hydrolysis reactions and in structured lipid synthesis. In shake flasks, yeast extract and urea were the best nitrogen sources for lipase production with PSR and their simultaneous use increased the lipase production even further. This result was confirmed in a 3.5-liter bioreactor, with lipase activity in an extracellular medium of 40 U/mL. A maximum reaction rate (Vmax) of 49.5 µmol/min/g, a Michaelis–Menten constant (Km) of 207 µmol/L, and a turnover number (Kcat) of 130 s−1 were determined for the new biocatalyst, fermPSR, for the hydrolysis of p-nitrophenyl laurate (p-NPL) into p-nitrophenol. The conversion of p-NPL into p-nitrophenol in subsequent reactions confirmed fermPSR’s potential for industrial hydrolytic reactions. The production of structured lipids from vegetable oil and free fatty acids by fermPSR evidences the versatility of this new biocatalyst.

A heat-resistant intracellular laccase immobilized via cross-linked enzyme aggregate preparation: Characterization, application in bisphenol A removal and phytotoxicity evaluation

Aureobasidium pullulans laccase was immobilized via cross-linked enzyme aggregate (CLEA) and deployed in bisphenol-A (BPA) removal. The immobilization and BPA removal processes were mathematically modeled. The CLEA-treated BPA was evaluated for phytotoxicity. The optimum conditions for CLEA resulting in the highest immobilization yield were ammonium sulfate (60% w/v), glutaraldehyde (30 mM), pH (4.5), time (6 h) and temperature (45 °C). The CLEA retained about 56% of its activity after twelve catalytic cycles. The optimum pH and temperature of the laccase CLEA were 5.5 and 60 °C respectively. The SEM indicated that the laccase CLEA was type II (unstructured). The data obtained from the heat inactivation kinetics and thermodynamic characterization indicated that the CLEA was stable to heat denaturation than the free enzyme. The kinetic parameters obtained for the CLEA with ABTS as substrate were 101.3 µM, 2.94 µmols^-1 mg^-1 and 0.03 dm³ s^-1 mg^-1 for the Km, Kcat and Kcat/Km respectively. The optimum conditions for BPA removal using the CLEA were temperature (30 °C), time (2 h), CLEA (1.0 mg) and BPA concentration (40 mg/L). After the 7th cycle, BPA removal by the laccase CLEA was 63 ± 2.3%. From the germination index values obtained, the CLEA-treated BPA solution showed no phytotoxicity to germinated S. bicolor seeds compared to the untreated (BPA-only) solutions.

Modeling of enzymatic activity of free β-glucosidase from palm weevil, Rhynchophorus palmarum Linn. (Coleoptera: Curculionidae) larvae: Effects of pH and temperature

Palm weevil, Rhynchophorus palmarum L., is an important pest of palm trees (Elaeis guineensis) around the tropical regions. Characterization of their digestive enzymes could be an important stage to develop appropriate pest control strategies. Study of these enzymes could also be of interest in different biotechnological applications. Among digestive enzymes, there is β-glucosidase which hydrolytically catalyzes the β-glycosidic linkage of glycosides. In the present work, the catalytic activity of β-glucosidase in the digestive juice of last larval instar of R. palmarum L. (Rpbgl) has been investigated using p-nitrophenyl-β-D-glucopyranoside (pNPG) as substrate. The "classical" physico-chemical properties for purified Rpbgl have been determined by the help of enzymatic activity modeling. Thus, the values of (325.4 ± 0.2) K, 5.28 ± 0.07 and (37.9 ± 0.6) kJ mol-1 were obtained for optimum temperature, optimum pH and activation energy, respectively. The pK values for enzyme-substrate complex are 4.25 ± 0.07 and 6.20 ± 0.07 for nucleophile and the proton donor, respectively. Enzyme kinetics study was also performed and the values of (127 ± 6) U mg-1 and (0.78 ± 0.08) mM were obtained for Vmax and Km, respectively. Using the Equilibrium model (EM), the thermal inactivation data were analyzed. ΔHeq, Teq, ΔGinact∗ and ΔGcat∗ were found to be (222 ± 4) kJ mol-1, (323.0 ± 0.1) K, (101.9 ± 0.2) kJ mol-1 and (53.37 ± 0.02) kJ mol-1, respectively. These results show that Rpbgl is less stable with a narrow temperature tolerance compared to other β-glucosidases.

Use of a Sequential Fermentation Method for the Production of Aspergillus tamarii URM4634 Protease and a Kinetic/Thermodynamic Study of the Enzyme

Microbial proteases are commonly produced by submerged (SmF) or solid-state fermentation (SSF), whose combination results in an unconventional method, called sequential fermentation (SF), which has already been used only to produce cellulolytic enzymes. In this context, the aim of the present study was the development of a novel SF method for protease production using wheat bran as a substrate. Moreover, the kinetic and thermodynamic parameters of azocasein hydrolysis were estimated, thus providing a greater understanding of the catalytic reaction. In SF, an approximately 9-fold increase in protease activity was observed compared to the conventional SmF method. Optimization of glucose concentration and medium volume by statistical means allowed us to achieve a maximum protease activity of 180.17 U mL−1. The obtained enzyme had an optimum pH and temperature of 7.0 and 50 °C, respectively. Kinetic and thermodynamic parameters highlighted that such a neutral protease is satisfactorily thermostable at 50 °C, a temperature commonly used in many applications in the food industry. The results obtained suggested not only that SF could be a promising alternative to produce proteases, but also that it could be adapted to produce several other enzymes.

A Comprehensive Review on Valorization of Agro-Food Industrial Residues by Solid-State Fermentation

Agro-food industrial residues (AFIRs) are generated in large quantities all over the world. The vast majority of these wastes are lignocellulosic wastes that are a source of value-added products. Technologies such as solid-state fermentation (SSF) for bioconversion of lignocellulosic waste, based on the production of a wide range of bioproducts, offer both economic and environmental benefits. The versatility of application and interest in applying the principles of the circular bioeconomy make SSF one of the valorization strategies for AFIRs that can have a significant impact on the environment of the wider community. Important criteria for SSF are the selection of the appropriate and compatible substrate and microorganism, as well as the selection of the optimal process parameters for the growth of the microorganism and the production of the desired metabolites. This review provides an overview of the management of AFIRs by SSF: the current application, classification, and chemical composition of AFIRs; the catalytic function and potential application of enzymes produced by various microorganisms during SSF cultivation on AFIRs; the production of phenolic compounds by SSF; and a brief insight into the role of SSF treatment of AFIRs for feed improvement and biofuel production.

Optimization of fermentation parameters for high-activity inulinase production and purification from Rhizopus oryzae by Plackett-Burman and Box-Behnken

The aim of study was to optimize fermentation parameters for inulinase production from Rhizopus oryzae by a statistical approach and to carry out purification of inulinase. Five isolated fungal strains were screen out inulin degradation by using Lugol's iodine solution. R. oryzae exhibited maximum zone of clearance around the colony and was used as an inulinase producer. The effect of carbon sources (inulin, glucose, maltose, sucrose, lactose, onion peel, stevia root, wheat bran) as medium component and fermentation parameters (temperature (25-45 °C), initial pH (4-7), time (3-7 days)) on inulinase production was investigated by Plackett-Burman Design. Wheat Bran (WB), temperature, pH, and incubation time were found to be significant for the production of inulinase (P < 0.05). Furthermore, Box-Behnken Design was employed to optimize fermentation conditions. The maximum experimental results for inulinase activity and specific activity were 348.36 EU/mL and 3621.78 EU/mg, respectively. The results were obtained at 5 days of incubation time, 35 °C of incubation temperature, initial pH of 5.5, and 2% (w/v) WB. Also, inulinase was purified by using ammonium sulfate precipitation, gel filtration chromatography with 2.19-fold and its molecular weight was found as 89.12 kDa. The optimal pH and temperature of the purified enzyme were 4.0 and 60 °C, respectively. Furthermore, the purified enzyme showed excellent stability at 60 °C. In conclusion, the present study offers cost-effective method to produce inulinase from Rhizopus oryzae. Also, it can be suggested that the purified inulinase has strong potential for usage in production of fructose syrup and other industrial areas.

Enzymatic hydrolysis of lignocellulosic biomass using native cellulase produced by Aspergillus niger ITV02 under liquid state fermentation

The objective of this work was to evaluate the biochemical characteristics of an enzymatic extract obtained from autochthonous fungus Aspergillus niger ITV02 and its application in the enzymatic hydrolysis of wheat straw and corn stubble pretreated by steam explosion. The enzymatic extract was obtained by submerged fermentation using delignified sweet sorghum bagasse as a carbon source. The results obtained showed that the enzymatic extract had β-glucosidase and endoglucanase activities. The effects of pH and temperature on cellulase activity were evaluated and its thermostability was determined. The optimal parameters of the β-glucosidase and endoglucanase activities obtained were pH 5 and 70 °C. The enzymatic extract of A. niger ITV02 was used to hydrolyze wheat straw and corn stubble, and the hydrolysis yields were compared with those obtained by a commercial cellulase (Celluclast 1.5L NS 50013) and CellicCTec3. The results showed that with the use the mixture of Celluclast 1.5L-A. niger ITV02 and CellicCTec3-A. niger ITV02 in the hydrolysis, conversions of 86.36% and 67.8% were obtained, respectively. Glucose production for the mixture extract increased 2.15 times more than when the enzyme was used independently alone. The present work shows that A. niger ITV02 has a potential as an enzyme producer for lignocellulosic hydrolysis.

Effect of temperature, pH and storage time on the stability of an extracellular fructosyltransferase from Aspergillus oryzae IPT-301

Abstract In this work, it was determined the influence of temperature, pH and storage time on the enzymatic activity and stability of an extracellular fructosyltransferase (FTase E.C.2.4.1.9) from Aspergillus oryzae IPT-301 produced by submerged fermentation. The thermodynamic parameters showed a tendency for increasing enzyme denaturation with the rise in temperature. The maximum transfructosylation activity was obtained at the incubation pH 5.5. During storage at 4 °C, the transfructosylation activity decreased, whereas the hydrolytic activity increased, especially in the first nine hours, a time in which the enzyme presented 45.6% of its initial transfructosylation activity. These results contributed to the improvement of the conditions of storage, immobilization and use of the soluble fructosyltransferases (FTase) in fructooligosaccharide (FOS) production.

Investigating the thermodynamic and kinetics properties of acid phosphatase extracted and purified from seedlings of Chenopodium murale

Herein acid phosphatase isoenzyme was extracted from the C. murale seedlings. The purification was accomplished by chromatographic techniques and passing through DEAE-cellulose and Sephadex G-100 column. The specific activity of acid phosphatase 5.75 U/mg of protein was obtained with 66 purification fold 15.8% yield and molecular mass was 29 kDa with very faint bands corresponding to 18 kDa and 14 kDa. The maximal activity at pH 5.0 and 50 °C best illustrated by first order kinetics. When temperature was raised (55 °C to 75 °C), the deactivation rate constant was increased from 0.001 to 0.014 min^-1, while half-life was decreased from 693 to 49 min^-1. The results of activity collected at different temperature were then used to estimate, activation energy of hydrolysis reaction (Ea = 47.59 kJmol^-1). A high Z-value (18.86 °C min^-1) was obtained indicating a less sensitivity towards temperatures. The residual activity examinations were carried out from 55 °C to 75 °C and assessing the Deactivation Energy (Ed 116.39 kJmol^-1), Enthalpy change (ΔH° 113.55kJmol^-1), Entropy change (ΔS° 110.33kJmol^-1) and change in Gibbs free energy (ΔG° 10.02 kJmol^-1). Taken together, thermodynamic parameters confirm the high stability of enzyme and show potential commercial applicability.

Kinetic/thermodynamic study of immobilized β-fructofuranosidase from Aspergillus tamarii URM4634 in chitosan beads and application on invert sugar production in packed bed reactor

β-fructofuranosidase (FFase) from Aspergillus tamarii URM4634 was immobilized covalently in chitosan beads. It was characterized biochemically, studied in terms of kinetic and thermodynamic parameters, and applied on conversion of sucrose for invert sugar production in a packed bed reactor (PBR). The optimum reactional conditions were determined and obtained at pH 5.0 and 60 °C. FFase was thermostable at 50-55°C. At 50°C, the enzyme shows longer half-life (t_1/2) (594.13 min) and a higher D-value (1,973.64 min). This indicates that immobilized FFase was stable at temperature commonly used in invert sugar production. The following thermodynamic parameters were obtained: activation energy (E*_d = 301.57 kJ mol^-1), enthalpy (298.76 ≤ ΔH*_d ≤ 298.89 kJ mol^-1), entropy (579.88 ≤ ΔS*_d ≤ 589.27 J K^-1 mol^-1) and Gibbs free energy (100.29 ≤ ΔG*_d ≤ 108.47 kJ mol^-1). The high E*_d, ΔH*_d and ΔG*_d values confirmed FFase thermostability. The high and positive values for ΔS*_d indicate an increase in disorder due opening of the enzyme structure. The sucrose hydrolysis in PBR showed a maximum invert sugar yield (96.0%) at 15 min of operation. The hydrolysis process remained efficient up to 100 min (70.22%). The results obtained in the present study provide a good indication that immobilized FFase on chitosan beads in PBR is efficient to invert sugar production for food industry.

Biochemical characterization of extracellular fructosyltransferase from Aspergillus oryzae IPT-301 immobilized on silica gel for the production of fructooligosaccharides

OBJECTIVE

Extracellular fructosyltransferase (FTase, E.C.2.4.1.9) from Aspergillus oryzae IPT-301 was immobilized on silica gel by adsorption and biochemically characterized aiming at its application in the transfructosylation reaction of sucrose for the production of fructooligossaccarides (FOS).

RESULTS

The transfructosylation activity (A_T) was maximized by the experimental design in function of the reaction pHs and temperatures. The A_T of the immobilized enzyme showed the kinetics behavior described by the Hill model. The immobilized FTase showed reuse capacity for six consecutive reaction cycles and higher pH and thermal stability than the soluble enzyme.

CONCLUSION

These results suggest a high potential of application of silica gel as support for FTase immobilization aiming at FOS production.

Investigating the Impact of Various Parameters On the Activity of Acid Phosphatases from Seedlings of Coronopus didymus

The thermal stability of purified acid phosphatase from the germinating seedlings of Coronopus didymus (Jangli halon) was investigated by studying the impact of various thermodynamic parameters [t_1/2, E_d, ΔH° (enthalpy change), ΔG° (free energy change), and ΔS° (entropy change)] of heat treatment in the temperature range of 55-75 °C. The thermal denaturation of acid phosphatase, assessed by loss in activity, was evidently followed by first-order kinetics, which varies with time and yield during the process of denaturation. The half-life of the enzyme was 693 min at 55 °C. The E_d (activation energy of denaturation) was calculated by the Arrhenius plot (30 kcal mol^-1), and the Z-value was 17.3 °C. The various thermodynamic parameters studied were as follows: ΔH°, the change in enthalpy of inactivation, was 121.93 kJ mol^-1 at 55 °C; ΔG°, the change in free energy of inactivation, was 110.65 kJ mol^-1 at 55 °C; and ΔS°, the change in entropy of inactivation, was 34.39 J mol^-1 k^-1 at 55 °C. This suggests that acid phosphatase activity is thermostable to long heat treatment up to 60 °C.

Production and characterization of an enzyme extract with cellulase activity produced by an indigenous strain of Fusarium verticillioides ITV03 using sweet sorghum bagasse

OBJECTIVES

To evaluate a strain of Fusarium verticillioides ITV03 isolated from wood residues in the Veracruz region of Mexico. Endoglucanase and β-glucosidase production by submerged fermentation was optimized using a Box-Behnken design, where the independent variables were urea, ammonium sulfate and yeast extract.

RESULTS

After optimization, an endoglucanase activity of 0.27 U/mL was achieved; subsequently, three carbon sources were evaluated (carboxymethyl cellulose, sweet sorghum bagasse cellulose and delignified sweet sorghum bagasse (DSSB). The results showed that DSSB yielded the greatest endoglucanase (0.28 U/mL) and β-glucosidase (0.12 U/mL) activities. Both enzymatic activities were characterized for the effect of pH, temperature and thermostability. The optimal parameters of β-glucosidase and endoglucanase activity were pH 5 and 4 respectively, the optimum temperature 60 °C. These enzymes were stable at 50 °C for 150.68 h and 8.54 h, with an activation energy (E_a(day)) of 265.55 kJ/mol and 44.40 kJ/mol respectively, for β-glucosidase and endoglucanase.

CONCLUSION

The present work shows that a native strain like F. verticillioides ITV03 using DSSB supplemented with nitrogen has a great potential as a producer of cellulase for lignocellulosic residue hydrolysis.

Stable immobilization of aldehyde ketone reductase mutants containing nonstandard amino acids on an epoxy resin via strain-promoted alkyne–azide cycloaddition

To avoid random chemical linkage and achieve precisely directed immobilization, mutant enzymes were obtained and immobilized using an incorporated reactive nonstandard amino acid (NSAA). For this purpose, aldehyde ketone reductase (AKR) was used as a model enzyme, and 110Y, 114Y, 143Y, 162Q and 189Q were each replaced with p-azido-l-phenylalanine (pAzF). Then, the mutant AKR was coupled to the functionalized support by strain-promoted alkyne–azide cycloaddition (SPAAC). The effects of the incorporation number and site of NSAAs on the loading and thermal stability of the immobilized AKR were examined. The results show that the mutant enzymes presented better specific activity than the wild type, except for AKR-110Y, and AKR-114Y showed 1.16-fold higher activity than the wild type. Moreover, the half-life (t_1/2) of the five-point immobilized AKR reached 106 h and 45 h, 13 and 7 times higher than that of the free enzyme at 30 °C and 60 °C, respectively. Comparison of these three types of enzymes shows that multi-point immobilization provides improved loading and thermal stability and facilitates one-step purification. We expect this platform to facilitate a fundamental understanding of precisely oriented and controllable covalent immobilization and enable bio-manufacturing paradigms for fine chemicals and pharmaceuticals.

Stable immobilization of aldehyde ketone reductase mutants containing non-standard amino acids on an epoxy resin via strain-promoted alkyne–azide cycloaddition.

A highly thermostable crude endoglucanase produced by a newly isolated Thermobifida fusca strain UPMC 901

A thermophilic Thermobifida fusca strain UPMC 901, harboring highly thermostable cellulolytic activity, was successfully isolated from oil palm empty fruit bunch compost. Its endoglucanase had the highest activity at 24 hours of incubation in carboxymethyl-cellulose (CMC) and filter paper. A maximum endoglucanase activity of 0.9 U/mL was achieved at pH 5 and 60 °C using CMC as a carbon source. The endoglucanase properties were further characterized using crude enzyme preparations from the culture supernatant. Thermal stability indicated that the endoglucanase activity was highly stable at 70 °C for 24 hours. Furthermore, the activity was found to be completely maintained without any loss at 50 °C and 60 °C for 144 hours, making it the most stable than other endoglucanases reported in the literature. The high stability of the endoglucanase at an elevated temperature for a prolonged period of time makes it a suitable candidate for the biorefinery application.

High cellulolytic activities in filamentous fungi isolated from an extreme oligotrophic subterranean environment (Catão cave) in Brazil

Isolation and screening of new fungal strains from extreme and understudied environments, such as caves, is a promising approach to find higher yields enzyme producers. Cellulolytic fungal strains isolated from a Brazilian cave were evaluated for their enzymatic production after submerged (SmF) and solid-state fermentation (SSF). After SmF, three strains were selected for their high enzymatic activities: Aspergillus ustus for endoglucanase (4.76 U/mg), Talaromyces bruneus for β-glucosidase (11.71 U/mg) and Aspergillus sp. (CBMAI 1926) for total cellulase (1.70 U/mg). After SSF, these strains, showed better yields compared to the reference strain Aspergillus niger 3T5B8. Aspergillus sp. (CBMAI 1926) stood out as a new species that expressed activity of total cellulases (0.10 U/mg) and low protein concentration (0.44 mg/mL). In conclusion, these isolated strains have a more efficient and promising cellulolytic enzyme complex that can be used in fermentation and saccharification processes with a lower protein concentration and a higher enzymatic activity than the reference strain. Therefore, beside the new genetic material characterized, our study highlights the benefits of cave extreme environments exploitation to find new potentially valuable strains.

Trehalose mediated stabilisation of cellobiase aggregates from the filamentous fungus Penicillium chrysogenum

Extracellular fungal cellobiases develop large stable aggregates by reversible concentration driven interaction. In-vitro addition of trehalose resulted in bigger cellobiase assemblies with increased stability against heat and dilution induced dissociation. In presence of 0.1 M trehalose, the size of aggregates increased from 344 nm to 494 nm. The increase in size was also observed in zymography of cellobiase. Activation energy of the trehalose stabilised enzyme (Ea = 220.9 kJ/mol) as compared to control (Ea = 257.734 kJ/mol), suggested enhanced thermostability and also showed increased resistance to chaotropes. Purified cellobiase was found to contain 196.27 μg of sugar/μg of protein. It was proposed that presence of glycan on protein's surface impedes and delays trehalose docking. Consequently, self-association of cellobiase preceded coating by trehalose leading to stabilisation of bigger cellobiase aggregates. In unison with the hypothesis, ribosylated BSA failed to get compacted by trehalose and developed into bigger aggregates with average size increasing from 210 nm to 328 nm. Wheat Germ Lectin, in presence of trehalose, showed higher molecular weight assemblies in DLS, native-PAGE and fluorescence anisotropy. This is the first report of cross-linking independent stabilisation of purified fungal glycosidases providing important insights towards understanding the aggregation and stability of glycated proteins.

PEGylation as an efficient tool to enhance cytochrome c thermostability: a kinetic and thermodynamic study

PEGylation of cytochrome-c preserves activity and increases thermal stability, favoring the protein application as a biosensor.

How to calculate thermostability of enzymes using a simple approach

Determination of thermostability of enzymes is of prime importance for their successful industrial applications and, yet, the published data has often been incompletely analyzed to assess the suitability of enzymes. It is possible to determine meaningful thermostability parameters from the routinely acquired data through a straightforward method that is not only more informative but also provides a means to compare thermostability of enzymes from different sources. Here, we describe a simple, effective, and economical way to determine enzyme thermostability. In our opinion, including this method in Biochemistry and Molecular Biology curricula will encourage students to include thermostability analysis in their future work, leading to a more meaningful approach to evaluate and compare enzymes. Furthermore, as the method requires minimum specialized equipment, the analysis will be particularly suitable for labs that cannot afford expensive setup. © 2018 by The International Union of Biochemistry and Molecular Biology, 46:398-402, 2018.

Biochemical Characterization, Thermal Stability, and Partial Sequence of a Novel Exo-Polygalacturonase from the Thermophilic Fungus Rhizomucor pusillus A13.36 Obtained by Submerged Cultivation

This work reports the production of an exo-polygalacturonase (exo-PG) by Rhizomucor pusillus A13.36 in submerged cultivation (SmC) in a shaker at 45°C for 96 h. A single pectinase was found and purified in order to analyze its thermal stability, by salt precipitation and hydrophobic interaction chromatography. The pectinase has an estimated Mw of approximately 43.5–47 kDa and optimum pH of 4.0 but is stable in pH ranging from 3.5 to 9.5 and has an optimum temperature of 61°C. It presents thermal stability between 30 and 60°C, has 70% activation in the presence of Ca²⁺, and was tested using citrus pectin with a degree of methyl esterification (DE) of 26%. E_a(d) for irreversible denaturation was 125.5 kJ/mol with positive variations of entropy and enthalpy for that and ΔG_(d) values were around 50 kJ/mol. The hydrolysis of polygalacturonate was analyzed by capillary electrophoresis which displayed a pattern of sequential hydrolysis (exo). The partial identification of the primary sequence was done by MS MALDI-TOF and a comparison with data banks showed the highest identity of the sequenced fragments of exo-PG from R. pusillus with an exo-pectinase from Aspergillus fumigatus. Pectin hydrolysis showed a sigmoidal curve for the Michaelis-Menten plot.

Catalytic, kinetic and thermodynamic properties of stabilized Bacillus stearothermophilus alkaline protease

Bacillus stearothermophilus alkaline protease was conjugated to several oxidized polysaccharides of different chemical structure. The conjugates were evaluated for the kinetic and thermodynamic stability. The conjugated enzyme with oxidized pectin had the highest retained activity (79.5%) and the highest half-life (T_1/2) at 50°C and pH 9.0. Compared to the native protease, the conjugated preparation exhibited lower activation energy (E_a), lower deactivation constant rate (k_d), higher T_1/2, and higher D values (decimal reduction time) within the temperature range of 50-60°C. The thermodynamic parameters for irreversible inactivation of native and conjugated protease indicated that conjugation significantly decreased entropy (ΔS*) and enthalpy (ΔH*) of deactivation. The calculated value of activation energy for thermal denaturation (E_ad) for the conjugated enzyme was 20.4KJmole^-1 higher over the native one. The results of thermodynamic analysis for substrate hydrolysis indicated that the enthalpy of activation (ΔH*) and free energy of activation (free energy of substrate binding) ΔG*_E-S and (ΔG*), (free energy of transition state) ΔG*_E-T values were lower for the modified protease. Similarly, there was significant improvement of k_cat, k_cat/K_m values. The enzyme proved to be metalloprotease and significantly stimulated by Ca²⁺ and Mg²⁺ whereas Hg²⁺, Fe³⁺ Cu²⁺ and Zn²⁺ inhibited the enzyme activity. There was no pronounced effect on substrate specificity after conjugation.