Comparative Cold Shock Expression and Characterization of Fungal Dye-Decolorizing Peroxidases

A Bjerkandera adust new strain as a potential biocontrol agent against wheat scab

Bjerkandera adusta can decompose polycyclic aromatic hydrocarbons including cellulose and lignin, but its roles in inhibiting plant pathogens are unclear. Here, the confrontation culture and greenhouse pot experiments were employed to study the control effect of B. adusta M1 on Fusarium graminearum and wheat scab. The results showed that B. adusta M1 fermentation broth (FB) inhibited the growth of F. graminearum, with an inhibition rate of 52.7-89.17%. FB had a significant control effect (72.14 ± 1.42%) on wheat scab, which was slightly lower than that of the chemical fungicide carbendazim (77.34 ± 1.76%). The growth rate was significantly higher in B. adusta M1 than in F. graminearum, indicating a strong competitiveness by B. adusta M1. The images from a scanning electron microscope showed substantial deformations of the hyphae of F. graminearum being penetrated by the hyphae of B. adusta M1, indicating a strong mycoparasitism by B. adusta M1. In addition, FB increased the activity of catalase, peroxidase, and phenylalanine ammonia-lyase in wheat leaves related to disease resistance and decreased the malondialdehyde production and cell membrane permeability. We conclude that B. adusta M1 is a promising fungal agent to control the detriment of F. graminearum to cereal growth in the field.

Improved Foods Using Enzymes from Basidiomycetes

Within the kingdom of fungi, the division Basidiomycota represents more than 30,000 species, some with huge genomes indicating great metabolic potential. The fruiting bodies of many basidiomycetes are appreciated as food (“mushrooms”). Solid-state and submerged cultivation processes have been established for many species. Specifically, xylophilic fungi secrete numerous enzymes but also form smaller metabolites along unique pathways; both groups of compounds may be of interest to the food processing industry. To stimulate further research and not aim at comprehensiveness in the broad field, this review describes some recent progress in fermentation processes and the knowledge of fungal genetics. Processes with potential for food applications based on lipases, esterases, glycosidases, peptidases and oxidoreductases are presented. The formation and degradation of colourants, the degradation of harmful food components, the formation of food ingredients and particularly of volatile and non-volatile flavours serve as examples. In summary, edible basidiomycetes are foods—and catalysts—for food applications and rich donors of genes to construct heterologous cell factories for fermentation processes. Options arise to support the worldwide trend toward greener, more eco-friendly and sustainable processes.

Dye Decoloring Peroxidase Structure, Catalytic Properties and Applications: Current Advancement and Futurity

Dye decoloring peroxidases (DyPs) were named after their high efficiency to decolorize and degrade a wide range of dyes. DyPs are a type of heme peroxidase and are quite different from known heme peroxidases in terms of amino acid sequences, protein structure, catalytic residues, and physical and chemical properties. DyPs oxidize polycyclic dyes and phenolic compounds. Thus they find high application potentials in dealing with environmental problems. The structure and catalytic characteristics of DyPs of different families from the amino acid sequence, protein structure, and enzymatic properties, and analyzes the high-efficiency degradation ability of some DyPs in dye and lignin degradation, which vary greatly among DyPs classes. In addition, application prospects of DyPs in biomedicine and other fields are also discussed briefly. At the same time, the research strategy based on genetic engineering and synthetic biology in improving the stability and catalytic activity of DyPs are summarized along with the important industrial applications of DyPs and associated challenges. Moreover, according to the current research findings, bringing DyPs to the industrial level may require improving the catalytic efficiency of DyP, increasing production, and enhancing alkali resistance and toxicity.

Mutational and structural analysis of an ancestral fungal dye-decolorizing peroxidase

Dye-decolorizing peroxidases (DyPs) constitute a superfamily of heme-containing peroxidases that are related neither to animal nor to plant peroxidase families. These are divided into four classes (types A, B, C, and D) based on sequence features. The active site of DyPs contains two highly conserved distal ligands, an aspartate and an arginine, the roles of which are still controversial. These ligands have mainly been studied in class A-C bacterial DyPs, largely because no effective recombinant expression systems have been developed for the fungal (D-type) DyPs. In this work, we employ ancestral sequence reconstruction (ASR) to resurrect a D-type DyP ancestor, AncDyPD-b1. Expression of AncDyPD-b1 in Escherichia coli results in large amounts of a heme-containing soluble protein and allows for the first mutagenesis study on the two distal ligands of a fungal DyP. UV-Vis and resonance Raman (RR) spectroscopic analyses, in combination with steady-state kinetics and the crystal structure, reveal fine pH-dependent details about the heme active site structure and show that both the aspartate (D222) and the arginine (R390) are crucial for hydrogen peroxide reduction. Moreover, the data indicate that these two residues play important but mechanistically different roles on the intraprotein long-range electron transfer process. DATABASE: Structural data are available in the PDB database under the accession number 7ANV.

Characterization of a Dye-Decolorizing Peroxidase from Irpex lacteus Expressed in Escherichia coli: An Enzyme with Wide Substrate Specificity Able to Transform Lignosulfonates

A dye-decolorizing peroxidase (DyP) from Irpex lacteus was cloned and heterologously expressed as inclusion bodies in Escherichia coli. The protein was purified in one chromatographic step after its in vitro activation. It was active on ABTS, 2,6-dimethoxyphenol (DMP), and anthraquinoid and azo dyes as reported for other fungal DyPs, but it was also able to oxidize Mn²⁺ (as manganese peroxidases and versatile peroxidases) and veratryl alcohol (VA) (as lignin peroxidases and versatile peroxidases). This corroborated that I. lacteus DyPs are the only enzymes able to oxidize high redox potential dyes, VA and Mn⁺². Phylogenetic analysis grouped this enzyme with other type D-DyPs from basidiomycetes. In addition to its interest for dye decolorization, the results of the transformation of softwood and hardwood lignosulfonates suggest a putative biological role of this enzyme in the degradation of phenolic lignin.

Monokaryotic Pleurotus sapidus Strains with Intraspecific Variability of an Alkene Cleaving DyP-Type Peroxidase Activity as a Result of Gene Mutation and Differential Gene Expression

The basidiomycete Pleurotus sapidus produced a dye-decolorizing peroxidase (PsaPOX) with alkene cleavage activity, implying potential as a biocatalyst for the fragrance and flavor industry. To increase the activity, a daughter-generation of 101 basidiospore-derived monokaryons (MK) was used. After a pre-selection according to the growth rate, the activity analysis revealed a stable intraspecific variability of the strains regarding peroxidase and alkene cleavage activity of PsaPOX. Ten monokaryons reached activities up to 2.6-fold higher than the dikaryon, with MK16 showing the highest activity. Analysis of the PsaPOX gene identified three different enzyme variants. These were co-responsible for the observed differences in activities between strains as verified by heterologous expression in Komagataella phaffii. The mutation S371H in enzyme variant PsaPOX_high caused an activity increase alongside a higher protein stability, while the eleven mutations in variant PsaPOX_low resulted in an activity decrease, which was partially based on a shift of the pH optimum from 3.5 to 3.0. Transcriptional analysis revealed the increased expression of PsaPOX in MK16 as reason for the higher PsaPOX activity in comparison to other strains producing the same PsaPOX variant. Thus, different expression profiles, as well as enzyme variants, were identified as crucial factors for the intraspecific variability of the PsaPOX activity in the monokaryons.

A DyP-Type Peroxidase of Pleurotus sapidus with Alkene Cleaving Activity

Alkene cleavage is a possibility to generate aldehydes with olfactory properties for the fragrance and flavor industry. A dye-decolorizing peroxidase (DyP) of the basidiomycete Pleurotus sapidus (PsaPOX) cleaved the aryl alkene trans-anethole. The PsaPOX was semi-purified from the mycelium via FPLC, and the corresponding gene was identified. The amino acid sequence as well as the predicted tertiary structure showed typical characteristics of DyPs as well as a non-canonical Mn²⁺-oxidation site on its surface. The gene was expressed in Komagataella pfaffii GS115 yielding activities up to 142 U/L using 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) as substrate. PsaPOX exhibited optima at pH 3.5 and 40 °C and showed highest peroxidase activity in the presence of 100 µM H₂O₂ and 25 mM Mn²⁺. PsaPOX lacked the typical activity of DyPs towards anthraquinone dyes, but oxidized Mn²⁺ to Mn³⁺. In addition, bleaching of β-carotene and annatto was observed. Biotransformation experiments verified the alkene cleavage activity towards the aryl alkenes (E)-methyl isoeugenol, α-methylstyrene, and trans-anethole, which was increased almost twofold in the presence of Mn²⁺. The resultant aldehydes are olfactants used in the fragrance and flavor industry. PsaPOX is the first described DyP with alkene cleavage activity towards aryl alkenes and showed potential as biocatalyst for flavor production.

Differential regulation of Pleurotus ostreatus dye peroxidases gene expression in response to dyes and potential application of recombinant Pleos-DyP1 in decolorization

Dye-decolorizing peroxidase (DyP) from the white rot basidiomycete Pleurotus ostreatus is a heme peroxidase able to oxidize diverse substrates, including recalcitrant phenols and dyes. This study analyzed the effect of chemical dyes on P. ostreatus growth, DyP activity and the expression of four Pleos-dyp genes during the time-course of Pleurotus ostreatus cultures containing either Acetyl Yellow G (AYG), Remazol Brilliant Blue R (RBBR) or Acid Blue 129 (AB129) dyes. Additionally, Pleos DyP1 was heterologously expressed in the filamentous fungus Trichoderma atroviride in order to explore the potential of a secreted recombinant enzyme for decolorizing different dyes in cultures and plate assays. The addition of dyes had an induction effect on the enzymatic activity, with the fermentations undertaken using RBBR and AYG dyes presenting the highest total DyP activity. DyP gene expression profiles displayed up/down regulation during the culture of three Pleos-dyp genes (Pleos-dyp1, Pleos-dyp2 and Pleos-dyp4), while Pleos-dyp3 transcript was not detected under any of the culture conditions studied. A 14-fold relative induction level (log2) increase for Pleos-dyp2 and Pleos-dyp4 in AB129 and AYG, respectively, was also found. The presence of AB129 resulted in the highest Pleos-dyp1 gene induction and repression level, corresponding to 11.83 and -14.6-fold relative expression and repression levels, respectively. The lowest expression level of all genes was observed in RBBR, a response which is associated with the growth phase. The filamentous fungus Trichoderma atroviride was successfully transformed for the heterologous expression of Pleos-dyp1. The modified strains (TaDyP) were able to decolorize mono-azo, di-azo, anthraquinone and anthracenedione dyes with extracellular DyP1 activity found in the culture supernatant. After 96 h of culture, the recombinant TaDyP strains were able to degrade (decolorize) 77 and 34% of 0.05mM AB129 and 0.25mM AYG, respectively.

Comprehensive investigation of a dye-decolorizing peroxidase and a manganese peroxidase from Irpex lacteus F17, a lignin-degrading basidiomycete

Irpex lacteus F17 is well-known for its ability to degrade recalcitrant aromatic pollutants, which mainly results from the action of the manganese peroxidase (MnP) that it is able to produce. Recently, the genome sequencing and annotation of this strain provided comprehensive picture of the ligninolytic peroxidase gene family. In addition to revealing the presence of 13 MnPs, genes for five dye-decolorizing peroxidases (DyPs) were also discovered in the I. lacteus F17 genome, which are unrelated to the fungal class II peroxidases. In the present study, amino acid sequences of five DyPs and 13 MnPs, representing two different families of heme peroxidases, were analyzed. Of these, two enzymes, a DyP (Il-DyP4) and a MnP (Il-MnP6) were expressed respectively in Escherichia coli, and were characterized by comparing their molecular models, substrate specificities, and catalytic features. The results showed that Il-DyP4 possessed a higher catalytic efficiency for some representative substrates, and a stronger decolorizing ability to a wide range of synthetic dyes in acidic conditions. Based on electrochemical measurements, Il-DyP4 was found to have a high redox potential of 27 mV at pH 3.5, which was superior to that of Il-MnP6 (− 75 mV), thereby contributing to its ability to oxidize high redox potential substrates, such as veratryl alcohol and polymeric dye Poly R-478. The results highlighted the potential of Il-DyP4 for use in industrial and environmental applications.

BadGluc, a β-glucosidase from Bjerkandera adusta with anthocyanase properties

A glycosidase of the basidiomycete Bjerkandera adusta (BadGluc) was found in screenings to possess a strong decolorizing ability towards malvidin-3-galactoside, an anthocyanin abundant in various berry fruits. The BadGluc was purified from the culture supernatant via FPLC, and the corresponding gene was identified which showed low similarity to other characterized glucosidases. Scanning the primary sequence with PROSITE no active site motif was detected. Eventually, a specific 18 aa consensus pattern was identified manually. The active site motif possessed an undescribed sequence which was only found in a few hypothetical proteins. The corresponding gene was cloned and expressed in Pichia pastoris GS115 yielding activities up to 100 U/L using 4-nitrophenyl-β-d-glucopyranoside (pNPG) as substrate. The enzyme possessed a good temperature (70% after 1 h at 50°C) and pH stability (70% between pH 2 and 7.5), and preferably catalysed the hydrolysis of delphinidin-3-glucoside and cyanidin-3-glucoside, regardless of the position of the terminal Hexa-His tag. This novel glucosidase worked in aqueous solution as well as on pre-stained fabrics making it the first known candidate anthocyanase for applications in the detergent and food industries.

Cell-free one-pot conversion of (+)-valencene to (+)-nootkatone by a unique dye-decolorizing peroxidase combined with a laccase from Funalia trogii

A combined system of a unique dye-decolorizing peroxidase (Ftr-DyP) and a laccase obtained from the basidiomycete Funalia trogii converted the precursor (+)-valencene completely to the high-value grapefruit flavour constituent (+)-nootkatone, reaching a concentration maximum of 1100 mg/L. In the presence of 1 mM Mn²⁺ and 2.5 mM p-coumaric acid, (+)-nootkatone was the predominating volatile product, and only traces of substrate and the nootkatols were detectable after 24 h. Hence, the two-enzyme-system reproduced the oxidizing activity observed before for the crude culture supernatant. The newly discovered Ftr-DyP was purified, sequenced and further characterized as a thermostable, non-glycosylated protein with a pH-optimum in the acidic range and a calculated mass of 52.3 kDa. Besides the typical activity of DyPs towards anthraquinone dyes, Ftr-DyP also oxidized Mn²⁺ and showed activity in the absence of hydrogen peroxide. Neither the DyP from Mycetinis scorodonius nor the manganese peroxidase from Nematoloma frowardii were able to replace Ftr-DyP in this reaction. A hypothetical reaction mechanism is presented.

Variants of PpuLcc, a multi-dye decolorizing laccase from Pleurotus pulmonarius expressed in Pichia pastoris

A laccase of the basidiomycete Pleurotus pulmonarius (PpuLcc) possessed strong decolorizing abilities towards artificial and natural dyes. The PpuLcc was purified from the culture supernatant via FPLC, and the corresponding gene cloned and expressed in Pichia pastoris GS115. To examine the impact of the C-terminal tail region and the signal peptide on the recombinant expression of PpuLcc, a non-modified version or different truncations (-2, -5, -13 AA) of the target protein were combined with different secretion signals. Heterologous expression of codon optimized constructs resulted in extracellular activities of the PpuLcc variants of up to 7000 U L^-1 (substrate ABTS) which was six times higher than non-codon optimized constructs. In contrast to previous works, altering the C-terminal end of the protein did not influence kinetic parameters or the rate of expression. The His-Tag purified enzymes showed high temperature optima (50-70 °C) and thermo stability. All of the recombinant variants degraded triarylmethane and azo dyes. Rapid bleaching of β-carotene (E 160a) and the polyene acid norbixin (E 160b) using a laccase was found for the first time. Thus, the enzyme may be useful in decolorizing unwanted polyene pigments, for example from the processing of cheese, bakery, desserts, ice cream or coloured casings.