Purification and characterization of an extracellular alkaline serine protease from Aspergillus terreus (IJIRA 6.2)

Fungal alkaline proteases and their potential applications in different industries

The consumption of various enzymes in industrial applications around the world has increased immensely. Nowadays, industries are more focused on incorporating microbial enzymes in multiple processes to avoid the hazardous effects of chemicals. Among these commercially exploited enzymes, proteases are the most abundantly used enzymes in different industries. Numerous bacterial alkaline proteases have been studied widely and are commercially available; however, fungi exhibit a broader variety of proteases than bacteria. Additionally, since fungi are often recognized as generally regarded as safe (GRAS), using them as enzyme producers is safer than using bacteria. Fungal alkaline proteases are appealing models for industrial use because of their distinct spectrum of action and enormous diversity in terms of being active under alkaline range of pH. Unlike bacteria, fungi are less studied for alkaline protease production. Moreover, group of fungi growing at alkaline pH has remained unexplored for their capability for the production of commercially valuable products that are stable at alkaline pH. The current review focuses on the detailed classification of proteases, the production of alkaline proteases from different fungi by fermentation (submerged and solid–state), and their potential applications in detergent, leather, food, pharmaceutical industries along with their important role in silk degumming, waste management and silver recovery processes. Furthermore, the promising role of alkali–tolerant and alkaliphilic fungi in enzyme production has been discussed briefly. This will highlight the need for more research on fungi growing at alkaline pH and their biotechnological potential.

Kinetics of growth and co-production of amylase and protease in novel marine actinomycete, Streptomyces lopnurensis KaM5

Amylases and proteases are among the industrially most important enzymes for food processing, animal feed, brewing, starch processing, detergents, healthcare, leather processing, and biofuel production. In this study, we investigated the growth kinetics and statistically optimized the co-production of amylase and protease in a phylogenetically novel haloalkaliphilic actinomycete, Streptomyces lopnurensis KaM5 of seawater. The Plackett-Berman design using Minitab 14.0 software was employed to assess the impact of the nutritional factors, temperature, pH, and incubation time. Further, starch, yeast extract, NaCl concentrations, and incubation time were optimized by Box-Behnken design at their three levels. The Pareto charts, contour, surface plots, and individual factorial analysis expressed the variability and levels for the optimal enzyme production. ANOVA analysis admitted the statistical fitness and significance level among the variables. A two-fold increase in enzyme production was achieved by cost-effective co-production media. The study was further extended to growth kinetics associated with enzyme production. Specific growth rate (μ), maximal cell mass (X_max), volumetric product formation (P_max), rate of product formation (Q_p), and generation time (g) were computed and analyzed. These parameters significantly improved when compared with the pre-optimized conditions, and the production economics of the enzyme was industrially viable. The initial studies on the characteristics of the enzymes suggested its ability to function under the combination of alkaline pH and high salt concentrations. The co-production of enzymes from extremophiles can be a potentially viable option for large-scale production and applications.

Biochemical characterization of a partially purified protease from Aspergillus terreus 7461 and its application as an environmentally friendly dehairing agent for leather industry

Proteases can be used in several biotechnological processes including detergent, food and leather industries. In the leather industry, dehairing is carried out by chemicals, which pollute the environment. Therefore, to make the hair removal process environmentally friendly, a protease produced by Aspergillus terreus has been purified, biochemically characterized and had an efficient ability to remove hair from bovine leather. The protease was produced using 1% wheat bran and was purified 2.3-fold using two chromatographic steps showing a molecular weight of 90 kDa. Optimal temperature and pH were 50 °C and 6.5, respectively. Thermal stability was up to 1 h at 50 °C. Protease was stable to detergents like Tween 80 and to organic solvents. The activity was activated by Ca²⁺ and inhibited by Hg²⁺ and Cu²⁺. The enzyme was classified as serine protease, by the inhibition by PMSF and was stable to reducing agents. It hydrolyzed casein, azocasein, BSA, egg albumin and BTpNA. The Km and Vmax values were 0.65 ± 0.03 mg/mL and 3.66 ± 0.18 μmol/min, respectively. Remarkable properties about temperature, pH, stability to detergents and reducing agents ensure that the protease from A. terreus can be an excellent candidate for industrial applications, particularly in the leather industry.

A Comparative Study of New Aspergillus Strains for Proteolytic Enzymes Production by Solid State Fermentation

A comparative study of the proteolytic enzymes production using twelve Aspergillus strains previously unused for this purpose was performed by solid state fermentation. A semiquantitative and quantitative evaluation of proteolytic activity were carried out using crude enzymatic extracts obtained from the fermentation cultures, finding seven strains with high and intermediate level of protease activity. Biochemical, thermodynamics, and kinetics features such as optimum pH and temperature values, thermal stability, activation energy (E a), quotient energy (Q 10), K m , and V max were studied in four enzymatic extracts from the selected strains that showed the highest productivity. Additionally, these strains were evaluated by zymogram analysis obtaining protease profiles with a wide range of molecular weight for each sample. From these four strains with the highest productivity, the proteolytic extract of A. sojae ATCC 20235 was shown to be an appropriate biocatalyst for hydrolysis of casein and gelatin substrates, increasing its antioxidant activities in 35% and 125%, respectively.

Purification and biochemical characterization of a novel alkaline protease produced by Penicillium nalgiovense

Penicillium nalgiovense PNA9 produces an extracellular protease during fermentation with characteristics of growth-associated product. Enzyme purification involved ammonium sulfate precipitation, dialysis, and ultrafiltration, resulting in 12.1-fold increase of specific activity (19.5 U/mg). The protein was isolated through a series of BN-PAGE and native PAGE runs. ESI-MS analysis confirmed the molecular mass of 45.2 kDa. N-Terminal sequencing (MGFLKLLKGSLATLAVVNAGKLLTANDGDE) revealed 93 % similarity to a Penicillium chrysogenum protease, identified as major allergen. The protease exhibits simple Michaelis-Menten kinetics and K m (1.152 mg/ml), V max (0.827 mg/ml/min), and k cat (3.2 × 10(2)) (1/s) values against azocasein show that it possesses high substrate affinity and catalytic efficiency. The protease is active within 10-45 °C, pH 4.0-10.0, and 0-3 M NaCl, while maximum activity was observed at 35 °C, pH 8.0, and 0.25 M NaCl. It is active against the muscle proteins actin and myosin and inactive against myoglobin. It is highly stable in the presence of non-ionic surfactants, hydrogen peroxide, BTNB, and EDTA. Activity was inhibited by SDS, Mn(2+) and Zn(2+), and by the serine protease inhibitor PMSF, indicating the serine protease nature of the enzyme. These properties make the novel protease a suitable candidate enzyme in meat ripening and other biotechnological applications.

Structural and functional characterization of mature forms of metalloprotease E495 from Arctic sea-ice bacterium Pseudoalteromonas sp. SM495

E495 is the most abundant protease secreted by the Arctic sea-ice bacterium Pseudoalteromonas sp. SM495. As a thermolysin family metalloprotease, E495 was found to have multiple active forms in the culture of strain SM495. E495-M (containing only the catalytic domain) and E495-M-C1 (containing the catalytic domain and one PPC domain) were two stable mature forms, and E495-M-C1-C2 (containing the catalytic domain and two PPC domains) might be an intermediate. Compared to E495-M, E495-M-C1 had similar affinity and catalytic efficiency to oligopeptides, but higher affinity and catalytic efficiency to proteins. The PPC domains from E495 were expressed as GST-fused proteins. Both of the recombinant PPC domains were shown to have binding ability to proteins C-phycocyanin and casein, and domain PPC1 had higher affinity to C-phycocyanin than domain PPC2. These results indicated that the domain PPC1 in E495-M-C1 could be helpful in binding protein substrate, and therefore, improving the catalytic efficiency. Site-directed mutagenesis on the PPC domains showed that the conserved polar and aromatic residues, D26, D28, Y30, Y/W65, in the PPC domains played key roles in protein binding. Our study may shed light on the mechanism of organic nitrogen degradation in the Arctic sea ice.

The Aspergillus nidulans pigP gene encodes a subunit of GPI-N-acetylglucosaminyltransferase which influences filamentation and protein secretion

Glycosylphosphatidylinositol (GPI) anchoring is the main mechanism allowing proper localization of secretory proteins in cell membranes. We have isolated an Aspergillus nidulans homolog of the human PIG-P gene, which encodes a subunit of acetylglucosaminyltransferase (GPI-GnT)-an enzyme involved in the synthesis of GPI anchors. A. nidulans pigP mutants have significantly decreased GPI synthesis. On solid media they show strong growth retardation (the "button" phenotype) while in liquid minimal media they show overall good growth but with hyperbranched and bulbous hyphae with impaired septation. Furthermore, the pigP strains, in contrast to the wild-type, abundantly secrete a 33-kDa alkaline serine protease (ALP) into the liquid medium.

Aspergillus flavus: an emerging non-fumigatus Aspergillus species of significance

Invasive aspergillosis is rare in immunocompetent people but contributes to significant morbidity and mortality in immunosuppressed patients. The majority (approximately 80%) of invasive Aspergillus infections is caused by Aspergillus fumigatus. The second most frequent (approximately 15-20%) pathogenic species is Aspergillus flavus and to a lesser extent, Aspergillus niger and Aspergillus terreus. Aspergillus flavus has emerged as a predominant pathogen in patients with fungal sinusitis and fungal keratitis in several institutions worldwide. To date, there has not been any publication exclusively reviewing the topic of A. flavus in the literature. This article reviews the microbiology, toxigenicity and epidemiology of A. flavus as well as describes the clinical characteristics, diagnosis and management of infections caused by this organism.

Purification, characterization and crystallization of an extracellular alkaline protease from Aspergillus nidulans HA-10

Aspergillus nidulans is a highly potent fungus used in the production of alkaline protease. Extracellular alkaline protease was purified from A. nidulans in a two-step procedure involving ammonium sulphate precipitation and Sephadex G-100 column chromatography. The molecular mass of the enzyme was determined to be 42 kDa by SDS-PAGE. The enzyme activity was also analyzed by zymogram with gelatin. The enzyme was more stable over a wide range of pH (6-10) and the temperatures up to 50 degrees C. It showed optimum enzyme activity at pH 8.0 and a temperature of 35 degrees C. The protease enzyme was completely inhibited by the serine protease inhibitor of phenylmethylsulfonyl fluoride (PMSF). The crystallization of the purified enzyme was performed by hanging drop vapour diffusion method using PEG 6000 as the precipitant. The micro crystals occurred in 40% of PEG 6,000.

Purification and Characterization of a Keratinase from a Feather-Degrading Fungus, Aspergillus flavus Strain K-03

A keratinolytic enzyme secreted by Aspergillus flavus K-03 cultured in feather meal basal medium (FMBM) containing 2% (w/v) chicken feather was purified and characterized. Keratinolytic enzyme secretion was the maximal at day 16 of the incubation period at pH 8 and 28℃. No relationship was detected between enzyme yield and increase of fungal biomass. The fraction obtained at 80% ammonium sulfate saturation showed 2.39-fold purification and was further purified by gel filtration in Sephadex G-100 followed by ion exchange chromatography on DEAE-Sephadex A-50, yielding an active protein peak showing 11.53-fold purification. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and zymograms indicated that the purified keratinase is a monomeric enzyme with 31 kDa molecular weight. The extracellular keratinase of A. flavus was active in a board range of pH (7~10) and temperature (30℃~70℃) profiles with the optimal for keratinase activity at pH 8 and 45℃. The keratinase activity was totally inhibited by protease inhibitors such as phenylmethylsulfonyl fluoride (PMSF), iodoacetic acid, and ethylenediaminetetraacetate (EDTA) while no reduction of activity by the addition of dithiothreitol (DTT) was observed. N-terminal amino acid sequences were up to 80% homologous with the fungal subtilisins produced by Fusarium culmorum. Therefore, on the basis of these characteristics, the keratinase of A. flavus K-03 is determined to be subtilisins-like.

Chymostatin can combine with pepstatin to eliminate extracellular protease activity in cultures of Aspergillus niger NRRL-3

Aspergillus strains are being considered as potential hosts for recombinant heterologous protein production because of their excellent extracellular enzyme production characteristics. However, Aspergillus proteases are problematic in that they modify and degrade the heterologous proteins in the extracellular medium. In previous studies we observed that media adjustments and maintenance of a filamentous morphology greatly reduced protease activity and that a low concentration of the aspartic protease inhibitor pepstatin inhibited the latter protease activity to the extent of approximately 90%. In this paper we report that when the serine protease inhibitor chymostatin is used in combination with pepstatin 99-100% of total protease activity in Aspergillus cultures is inhibited. In protease assays a concentration of 30 microM chymostatin combined with 0.075 microM pepstatin was required for maximum inhibition. Inhibitor concentrations of chymostatin and pepstatin of 120 and 0.3 microM, respectively, when added to Aspergillus cultures, has no significant effect on biomass production, glucose utilization or culture pH pattern. The potential of using these protease inhibitors in cultures of recombinant Aspergillus strains producing heterologous proteins will now be investigated to determine if the previously observed recombinant protein denaturing effects of Aspergillus proteases can be negated.

Production and Biochemical Characterization of Insecticidal Enzymes from Aspergillus fumigatus Toward Callosobruchus maculatus

In the present work, Aspergillus fumigatus is described as a higher producer of hydrolytic enzymes secreted in response to the presence of the Callosobruchus maculatus bruchid pest. This fungus was able to grow over cowpea weevil shells as a unique carbon source, secreting alkaline proteolytic and chitinolytic enzymes. Enzyme secretion in A. fumigatus was induced by both C. maculatus exoskeleton as well as commercial chitin, and alkaline proteolytic and chitinolytic activities were detected after 48 hours of growth. Furthermore, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the production of specific proteins. Among them, two extracellular alkaline proteinases from culture enriched with C. maculatus exoskeleton were purified after chromatographic procedures using ion exchange and affinity columns. These proteins, named AP15 and AP30, had apparent molecular masses of 15,500 and 30,000 Da, respectively, as estimated by SDS-PAGE electrophoresis and mass spectrometry. AP30 was classified as a serine proteinase because it was inhibited by 5 mM: phenylmethylsulfonyl fluoride (100%) and 50 microM leupeptin (67.94%).

Purification and characterization of an extracellular protease from Penicillium chrysogenum Pg222 active against meat proteins

An extracellular protease from Penicillium chrysogenum (Pg222) isolated from dry-cured ham has been purified. The purification procedure involved several steps: ammonium sulfate precipitation, ion-exchange chromatography, filtration, and separation by high-performance liquid chromatography. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis and gel filtration, the purified fraction showed a molecular mass of about 35 kDa. The hydrolytic properties of the purified enzyme (EPg222) on extracted pork myofibrillar proteins under several conditions were evaluated by SDS-PAGE. EPg222 showed activity in the range of 10 to 60 degrees C in temperature, 0 to 3 M NaCl, and pH 5 to 7, with maximum activity at pH 6, 45 degrees C, and 0.25 M NaCl. Under these conditions the enzyme was most active against tropomyosin, actin, and myosin. EPg222 showed collagenolytic activity but did not hydrolyze myoglobin. EPg222 showed higher activity than other proteolytic enzymes like papain, trypsin, and Aspergillus oryzae protease. The N-terminal amino acid sequence was determined and was found to be Glu-Asn-Pro-Leu-Gln-Pro-Asn-Ala-Pro-Ser-Trp. This partial amino acid sequence revealed a 55% homology with serine proteases from Penicillium citrinum. The activity of this novel protease may be of interest in ripening and generating the flavor of dry-cured meat products.