Biogenic synthesis and cytotoxic effects of silver nanoparticles mediated by white rot fungi

Silver nanoparticles (AgNPs) were successfully synthesized using silver nitrate via the biological route using the culture filtrate of Ganoderma enigmaticum as well as Trametes ljubarskyi white rot fungi materials at room temperature. The proposed synthetic technique was applied for the first time for AgNPs preparation via the biological route through a low-cost pathway, which considered as an adequate direction of preparation compared to the commercial methods. This study reports the in vitro cytotoxic effect of biologically synthesized AgNPs in disposing of the human lung cancer cell line (A549) and human breast cancer cell (MCF-7) by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. In addition, the viability of the tested cell lines was tested after treatment for 24 h in the presence of the prepared nanoparticles. The obtained results indicated the reduced viability of cancer cell lines with improving concentrations of AgNPs (40-120 μg/mL) at 24 h. Furthermore, at 120 μg/mL concentration, the fungal nanoparticles showed substantial cytotoxic effects toward the treated cells. Consequently, the results designated that the biologically synthesized silver nanoparticles have effective behavior for treating A549 and MCF-7 cancer cells from the laboratory experiment approach; however, additional studies are required to validate these results in vivo models as anticancer agents depending on their cytotoxic activity.

Proteomic insight on the polychlorinated biphenyl degrading mechanism of Pleurotus pulmonarius LBM 105

White-rot fungi are well known bioremediation agents capable of removing recalcitrant xenobiotics. However, the molecular mechanism involved in this process is not well understood. The aim of the present study was to compare the proteomic profiles of Pleurotus pulmonarius LBM 105 in presence and absence of a mixture of polychlorinated biphenyls. Cultures of the fungus were spiked with a mixture of Aroclors and cultivated for 28 days. This strain achieved a peak of PCBs-removal of 65.50 ± 8.09% after 21 days. The ecotoxicological assays showed a toxicity reduction of 46.47%. Based on these findings, a proteomic study was carried out and it was proven that the oxidative metabolism was highly affected. Two proteins that have a function at the transcriptional level and related to the oxidative metabolism, the glyceraldehyde-3-phosphate dehydrogenase and the basal transcription factor 3, presented an increase in their quantity in PCBs presence. Several oxidases and reductases were highly induced, presenting the short chain reductases, aldo/keto reductases, laccases and versatile peroxidases as the enzymes with the most notorious changes. These results indicate a complex response of the fungal metabolism towards these pollutants, which includes a transcriptional response to the oxidative stress and a modification of the intra- and extra-cellular enzymatic profile.

White rot fungi can be a promising tool for removal of bisphenol A, bisphenol S, and nonylphenol from wastewater

Endocrine-disrupting chemicals (EDC) are a wide group of chemicals that interfere with the endocrine system. Their similarity to natural steroid hormones makes them able to attach to hormone receptors, thereby causing unfavorable health effects. Among EDC, bisphenol A (BPA), bisphenol S (BPS), and nonylphenol (NP) seem to be particularly harmful. As the industry is experiencing rapid expansion, BPA, BPS, and NP are being produced in growing amounts, generating considerable environmental pollution. White rot fungi (WRF) are an economical, ecologically friendly, and socially acceptable way to remove EDC contamination from ecosystems. WRF secrete extracellular ligninolytic enzymes such as laccase, manganese peroxidase, lignin peroxidase, and versatile peroxidase, involved in lignin deterioration. Owing to the broad substrate specificity of these enzymes, they are able to remove numerous xenobiotics, including EDC. Therefore, WRF seem to be a promising tool in the abovementioned EDC elimination during wastewater treatment processes. Here, we review WRF application for this EDC removal from wastewater and indicate several strengths and limitations of such methods.

Lignin degradation and nutrient cycling by white rot fungi under the influence of pesticides

The production of enzymes involved in lignin degradation (laccase, ligninase), carbon cycling (β-glucosidase), and phosphorous cycling (phosphomonoesterase) by white rot fungi (Pleurotus sajor-caju) was studied. In the presence of chlorpyrifos, carbofuran, and their mixture, laccase activity was highest on the 7th day, i.e., 192.5 ± 0.31 U ml^- 1, 213.6 ± 0.31 U ml^- 1, and 164.6 ± 0.31 U ml^- 1, respectively, compared to the control which produced maximum laccase on the 14th day (126.9 ± 0.15 U ml^- 1). Phosphomonoesterase activity in the presence of chlorpyrifos, carbofuran, and their mixture was 31.5 ± 0.25, 24.1 ± 0.15, and 29.2 ± 0.35 µg PNP min^-1 ml^-1, respectively, which was more than the control on the 21st day (11.63 ± 0.21 µg PNP min^-1 ml^-1). β-Glucosidase production increased with the days of incubation in the presence of pesticides than in the control. β-Glucosidase activity on the 21st day in the presence of chlorpyrifos, carbofuran, and their mixture was 32.4 ± 0.1, 24.2 ± 0.3, and 28.4 ± 0.25 µg PNP min^-1 ml^-1, respectively, as compared to control (15.3 ± 0.6 µg PNP min^-1 ml^-1). Thus, chlorpyrifos, carbofuran, and their mixture were found to have a positive effect on the production of laccase, β-glucosidase, and phosphomonoesterase by P. sajor-caju, which can use these pesticides as a source of their nutrition, thereby improving the health of pesticide-polluted soils.

Trametes versicolor immobilized on rotating biological contactors as alternative biological treatment for the removal of emerging concern micropollutants

White rot fungi have been studied for the removal of micropollutants of emerging concern from wastewater during the last decade. However, several issues need to be overcome for its plausible implementation at full-scale installations such as the addition of supplementary substrates, the partial re-inoculation of fresh fungi or the use of extended hydraulic retention times. This work proposes the immobilization of Trametes versicolor on rotating biological contactors at bench scale (flowrates of 10 L/d and reactor capacity of 10 L) for the treatment of different urban wastewater. This type of bioreactor achieved remarkable reductions of the total organic carbon loading of the wastewater (70-75%) in a wide range of C:N and C:P ratios with limited addition of supplementary substrates, non-refreshment of the fungal biomass and only 1-day of hydraulic retention. The addition of gallic acid as quinone-like mediator and quelated iron and manganese complexes increased the removal of pharmaceutical micropollutants mediated by the so-called advanced bio-oxidation process. The immobilization of Trametes versicolor on rotating biological contactors also showed a remarkable stabilization of the fungi during the continuous treatment of different urban wastewater under non-sterile conditions. Thus, this system is a sound alternative for biological urban wastewater treatment with pharmaceutical removal because overcome all the problems usually associated with the water treatment technologies based on white rot fungi that makes difficult the scaling-up of the process and its implementation in full scale wastewater treatment plants.

Evaluation of white rot fungi pretreatment of mushroom residues for volatile fatty acid production by anaerobic fermentation: Feedstock applicability and fungal function

White rot fungi using P. sajor-caju and T. versicolor was examined to pretreat raw champost (lignin-rich) and oyster champost (cellulose-rich) for enhancement of fermentative volatile fatty acid (VFA) production. Results showed that the efficiency of pretreatment and VFA production was influenced by the fungal strains and substrates. P. sajor-caju pretreatment showed preferential lignin degradation on raw champost and obtained the maximum VFA yield (203 ± 9 mg COD/g VS_added), which increased by 60% and 74% compared to that of control and unpretreated champost, respectively. For cellulose-rich oyster champost, however, fungal pretreatment decreased VFA yield compared to unpretreated champost. Further mechanisms analysis demonstrated the two strains grow and secreted ligninolytic enzymes, which substantially influenced the characteristics of two champosts such as cellulose/lignin ratio and morphology in different extents. P. sajor-caju was highly efficient to lignin-rich champost on selectively degrading lignin and further enhancing digestibility such as VFA production.

A proposed stepwise screening framework for the selection of polycyclic aromatic hydrocarbon (PAH)-degrading white rot fungi

This study suggests a simple three-step screening protocol for the selection of white rot fungi (WRF) capable of degrading polycyclic aromatic hydrocarbons (PAHs), which combines easily applicable bioassay techniques, and verifies that protocol by evaluating the PAH degradation activity, ligninolytic enzyme secretion, and relevant gene expressions of the selected PAH-degraders. Using 120 fungal strains, a sequence of bioassay techniques was applied: Bavendamm's reaction (Step 1), remazol brilliant blue R (RBBR) decolorization (Step 2); assays for tolerance to four mixed PAHs-phenanthrene, anthracene, fluoranthene, and pyrene (Step 3). This stepwise protocol selected 14 PAH-degrading WRF, including Microporus vernicipes, Peniophora incarnata, Perenniporia subacida, Phanerochaete sordida, Phlebia acerina, and Phlebia radiata. Of these, P. incarnata exhibited the highest PAH degradative activity, ranging from 40 to > 90%, which was related to the time-variable secretions of three extracellular ligninolytic enzymes: laccase, manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP). Laccase and MnP production by P. incarnata tended to be greater in the early stages of PAH degradation, whereas its LiP production became intensified with decreasing laccase and MnP production. Pilc1 and pimp1 genes encoding laccase and MnP were expressed, indicating the occurrence of extracellular enzyme-driven biodegradation of PAH by the fungal strains.

Novel strategy to improve the colonizing ability of Irpex lacteus in non-sterile wheat straw for enhanced rumen and enzymatic digestibility

Pretreatment with white rot fungi is a promising method to enhance the digestibility of lignocelluloses; however, sterilization of feedstocks prior to inoculation is one of the costliest steps. To improve the colonizing ability of white rot fungi under non-sterile condition, Irpex lacteus, Pleurotus ostreatus, and Phanerochaete chrysosporium were inoculated in the wheat straw ensiled for 28 days and incubated for 56 days to determine the changes in microbe counts, organic acid content, chemical composition, and rumen and enzymatic digestibility. Results showed that ensiling produced abundant organic acids and suppressed most microbes in wheat straw. Significant growth of I. lacteus was observed after 3 days of incubation, and molds were only detectable at day 7 in the group. At the end of incubation, aerobic bacteria and lactic acid bacteria decreased by 18% and 38% in the wheat straw treated with I. lacteus, but molds, aerobic bacteria, and lactic acid bacteria thrived in those treated with P. ostreatus and P. chrysosporium. Even more, P. ostreatus and P. chrysosporium increased the lignin content of the ensiled wheat straw by 34% and 65%. However, I. lacteus selectively degraded lignin by 28% and improved the rumen and enzymatic digestibility by 18% and 34%. The finding indicates that ensiling prior to fermentation with I. lacteus is an effective method to control spoilage microbes and to enhance the rumen and enzymatic digestibility of wheat straw.

Exploiting the potential of metal and solvent tolerant laccase from Tricholoma giganteum AGDR1 for the removal of pesticides

Laccase from previously reported hardwood degrading fungus, Tricholoma giganteum AGDR1, was isolated, identified at molecular level, biochemically characterized and also utilized for pesticide degradation. Laccase gene is comprised of 3752 bp, which encompassed 742-bp of 5' flanking upstream sequence with 12 introns and 12 exons. Mature enzyme possesses 391 amino acids and signal peptide, which is determined to be monomeric protein with an apparent molecular weight of 41 kDa and 6.45 pI. Higher optimal activities were observed at 45 °C and pH 3.0 and surprisingly, it exhibited more than 20% of relative activity at pH 1.5. Purified laccase was tolerant to 100 mM of metals (i.e. Se, Pb, Cu, Cr and Cd), organic solvents (ethyl acetate, methanol, ethanol and acetone) and potent inhibitors (hydroxylamine, thiourea, NaF and Na-azide) as compared to reported laccases. It was able to degrade 29%, 7% and 72% of chlorpyrifos, profenofos and thiophanate methyl within 15 h, respectively. Molecular docking analysis revealed that higher binding efficacy of these pesticides is observed with H83, H320, A95, V384, and P366 which are presented near to the catalytic site. Based on the results, T. giganteum AGDR1 laccase can be applied for the potential remediation and industrial applications under harsh conditions.

Dye-decolorizing peroxidases in Irpex lacteus combining the catalytic properties of heme peroxidases and laccase play important roles in ligninolytic system

BACKGROUND

The white rot fungus Irpex lacteus exhibits a great potential in biopretreatment of lignocellulose as well as in biodegradation of xenobiotic compounds by extracellular ligninolytic enzymes. Among these enzymes, the possible involvement of dye-decolorizing peroxidase (DyP) in lignin degradation is not clear yet.

RESULTS

Based on the extracellular enzyme activities and secretome analysis, I. lacteus CD2 produced DyPs as the main ligninolytic enzymes when grown in Kirk's medium supplemented with lignin. Further transcriptome analysis revealed that induced transcription of genes encoding DyPs was accompanied by the increased expression of transcripts for H₂O₂-generating enzymes such as alcohol oxidase, pyranose 2-oxidase, and glyoxal oxidases. Meanwhile, accumulation of transcripts for glycoside hydrolase and protease was observed, in agreement with abundant proteins. Moreover, the biochemical analysis of IlDyP2 and IlDyP1 confirmed that DyPs were able to catalyze the oxidation of typical peroxidases substrates ABTS, phenolic lignin compounds DMP, and guaiacol as well as non-phenolic lignin compound, veratryl alcohol. More importantly, IlDyP1 enhanced catalytic activity for veratryl alcohol oxidation in the presence of mediator 1-hydroxybenzotriazole, which was similar to the laccase/1-hydroxybenzotriazole system.

CONCLUSIONS

The results proved for the first time that DyPs depolymerized lignin individually, combining catalytic features of different peroxidases on the functional level. Therefore, DyPs may be considered an important part of ligninolytic system in wood-decaying fungi.

Transcription of lignocellulose-decomposition associated genes, enzyme activities and production of ethanol upon bioconversion of waste substrate by Phlebia radiata

Previously identified twelve plant cell wall degradation-associated genes of the white rot fungus Phlebia radiata were studied by RT-qPCR in semi-aerobic solid-state cultures on lignocellulose waste material, and on glucose-containing reference medium. Wood-decay-involved enzyme activities and ethanol production were followed to elucidate both the degradative and fermentative processes. On the waste lignocellulose substrate, P. radiata carbohydrate-active enzyme (CAZy) genes encoding cellulolytic and hemicellulolytic activities were significantly upregulated whereas genes involved in lignin modification displayed a more complex response. Two lignin peroxidase genes were differentially expressed on waste lignocellulose compared to glucose medium, whereas three manganese peroxidase-encoding genes were less affected. On the contrary, highly significant difference was noticed for three cellulolytic genes (cbhI_1, eg1, bgl1) with higher expression levels on the lignocellulose substrate than on glucose. This indicates expression of the wood-attacking degradative enzyme system by the fungus also on the recycled, waste core board material. During the second week of cultivation, ethanol production increased on the core board to 0.24 g/L, and extracellular activities against cellulose, xylan, and lignin were detected. Sugar release from the solid lignocellulose resulted with concomitant accumulation of ethanol as fermentation product. Our findings confirm that the fungus activates its white rot decay system also on industrially processed lignocellulose adopted as growth substrate, and under semi-aerobic cultivation conditions. Thus, P. radiata is a good candidate for lignocellulose-based renewable biotechnology to make biofuels and biocompounds from materials with less value for recycling or manufacturing.

Simultaneous removal of ciprofloxacin, norfloxacin, sulfamethoxazole by co-producing oxidative enzymes system of Phanerochaete chrysosporium and Pycnoporus sanguineus

Pycnoporus sanguineus could remove 98.5% ciprofloxacin (CIP), 96.4% norfloxacin (NOR), 100% sulfamethoxazole (SMX), and 100% their mixture through biotransformation within 2 d, while Phanerochaete chrysosporium could only remove 64.5% CIP, 73.2% NOR, and 63.3% SMX through biosorption and biotransformation within 8 d, respectively. The efficiencies of antibiotic bioremoval under co-culture were more than that under the pure culture of P. chrysosporium but less than that under the pure culture of P. sanguineus. However, only 2% CIP and 3% NOR under co-culture were detected in the mycelia. In vitro enzymatic degradation and in vivo cytochrome P450 inhibition experiments revealed that laccase and cytochrome P450 could play roles in the removal of above all antibiotics, while manganese peroxidase could only play role in SMX removal. Transformation products of CIP and NOR under the pure culture of P. chrysosporium could be assigned to three different reaction pathways: (i) defluorination or dehydration, (ii) decarboxylation, and (iii) oxidation of the piperazinyl substituent. Additionally, other pathways, (iv) monohydroxylation, and (v) demethylation or deethylation at position N₁ also occurred under the co-culture and pure culture of P. sanguineus. Antibacterial activity of antibiotics could be eliminated after treatments with pure and co-culture of P. chrysosporium and P. sanguineus. The cytotoxicity of the metabolites of SMX and NOR under co-culture was lower than that under the pure culture of P. sanguineus, indicating co-culture is a more environmentally friendly strategy to eliminate SMX and NOR.

Stropharia rugosoannulata and Gymnopilus luteofolius: Promising fungal species for pharmaceutical biodegradation in contaminated water

Pharmaceuticals are environmental micropollutants that pose an emerging challenge because they are poorly eliminated in conventional wastewater treatment plants. Over the last decade, many attempts have been made to solve this problem, and wastewater fungal treatment is a promising alternative. In this study, six different ligninolytic fungi (Trametes versicolor, Ganoderma lucidum, Irpex lacteus, Stropharia rugosoannulata, Gymnopilus luteofolius and Agrocybe erebia) were studied as bioremediation candidates for the removal and degradation of six recalcitrant pharmaceutical micropollutants: Carbamazepine (CBZ), Venlafaxine (VFX), Iopromide (IPD), Diclofenac (DCF), Cyclophosphamide (CFD) and Ifosfamide (IFD). Self-immobilization in a pellet shape was achieved for all fungal mycelia (which was the first time that this was reported for S. rugosoannulata, G. luteofolius, and A. erebia). Biodegradation achievement was greater than 90% for IPD with G. luteofolius and greater than 70% for CBZ with S. rugosoannulata, which suggests a great potential for this alternative biological treatment. Besides, this was the first report where fungal treatment achieved CFD and IFD removals greater than 20% for the treatment with T. versicolor, G. lucidum and S. rugosoannulata.

Lignocellulosic waste valorisation strategy through enzyme and biogas production

Lignocellulosic wastes are generally pre-treated to facilitate the hydrolysis stage during the anaerobic digestion process. A process consisting of solid state fermentation carried out by white rot fungi and anaerobic digestion was evaluated on corn stover to produce ligninolytic enzymes and biogas. The enzyme production was quantified every 3d for a month at 30°C, and three fungal strains and two particle sizes of waste were compared. Of the main outcomes, Pleurotus eryngii produced the highest laccase enzyme activity compared with Pleurotus ostreatus and Trametes versicolor. Furthermore, this activity was improved by 16% when copper was used as an enzyme inducer. On the other hand, most of the conditions studied showed a decrease in maximum biogas production compared with untreated waste, the addition of copper decreased biogas production by 20%. Despite the above, Pleurotus eryngii showed promising results allowing a 19% increase of biogas production and high enzyme production values.

Minimum cocktail of cellulolytic multi-enzyme complexes obtained from white rot fungi via solid-state fermentation

The objective of this work was to optimize the total cellulase activity of the crude extract cocktails from five white rot fungi produced by solid-state fermentation, by means of the central composite design. The white rot fungi Pleurotus ostreatus PLO 06, Pleurotus eryngii PLE 04, Trametes versicolor TRAM 01, Pycnosporus sanguineus PYC 02 and Phanerochaete chrysosporium PC were tested. For optimization process aiming at the maximum value of total cellulase activity (FPAse), the multi-enzyme cellulase complexes (crude extracts) of each fungus were mixed simultaneously in different proportions. There was increase in FPAse activity for the cocktails formed by the extracts of the five fungi together, compared to the extracts of each fungus alone. The model presented the minimum cocktail of enzymes for maximum total cellulase activity, with 100.00 μL PYC; 100.00 μL PC; 100.00 μL PLO06; 100.00 μL PLE04 and 200 μL TRAM01. The maximum value found was of 304.86 U/L. The result of the cocktails was very relevant, showing that there is an enzymatic complementation in the extracts that should be further studied. Concentrated extract cocktails should also be evaluated for biomass saccharification.

Lignocellulosic waste valorisation strategy through enzyme and biogas production

Lignocellulosic wastes are generally pre-treated to facilitate the hydrolysis stage during the anaerobic digestion process. A process consisting of solid state fermentation carried out by white rot fungi and anaerobic digestion was evaluated on corn stover to produce ligninolytic enzymes and biogas. The enzyme production was quantified every 3d for a month at 30°C, and three fungal strains and two particle sizes of waste were compared. Of the main outcomes, Pleurotus eryngii produced the highest laccase enzyme activity compared with Pleurotus ostreatus and Trametes versicolor. Furthermore, this activity was improved by 16% when copper was used as an enzyme inducer. On the other hand, most of the conditions studied showed a decrease in maximum biogas production compared with untreated waste, the addition of copper decreased biogas production by 20%. Despite the above, Pleurotus eryngii showed promising results allowing a 19% increase of biogas production and high enzyme production values.

Comparative transcriptomic analysis of Cerrena unicolor revealed differential expression of genes engaged in degradation of various kinds of wood

To explore the number of enzymes engaged by Cerrena unicolor FCL139 for wood degradation, the transcriptomes of the fungus growing on birch, ash, maple sawdust and the control liquid medium were analyzed. Among 12,966 gene models predicted for the C. unicolor genome, 10,396 all-unigenes were detected, of which 9567 were found to be expressed in each of the tested growth media. The highest number (107) of unique transcripts was detected during fungus growth in the control liquid medium, while the lowest number (11) - in the fungal culture comprising maple saw dust. Analysis of C. unicolor transcriptomes identified numerous genes whose expression differed substantially between the mycelia growing in control medium and each of the sawdust media used, with the highest number (828) of upregulated transcripts observed during the fungus growth on the ash medium. Among the 294 genes that were potentially engaged in wood degradation, the expression of 59 was significantly (p < .01) changed in the tested conditions. The transcripts of 37 of those genes were at least four times more abundant in the cells grown in all sawdust media when compared to the control medium. Upregulated genes coding for cellulases and, to a lower extent, hemicellulases predominated during fungus growth on sawdust. Transcripts encoding cellulolytic enzymes were the most abundant in mycelia grown on birch and maple while lower number of such transcripts was detected in fungus growing on ash. The expression pattern of lignolytic activities-coding genes was strongly dependent on the type of sawdust applied for fungus growth medium.

Fungal treatment of humic-rich industrial wastewater: application of white rot fungi in remediation of food-processing wastewater

This paper presents the results of fungal treatment of a real industrial wastewater (WW), providing insight into the main mechanisms involved and clarifying some ambiguities and uncertainties in the previous reports. In this regard, the mycoremediation potentials of four strains of white rot fungi (WRF): Phanerochaete chrysosporium, Trametes versicolor, Pleurotus ostreatus and Pleurotus pulmonarius were tested to remove humic acids (HA) from a real humic-rich industrial treated WW of a food-processing plant. The HA removal was assessed by color measurement and size-exclusion chromatography (SEC) analysis. T. versicolor showed the best decolorization efficiency of 90% and yielded more than 45% degradation of HA, which was the highest among the tested fungal strains. The nitrogen limitation was studied and results showed that it affected the fungal extracellular laccase and manganese peroxidase (MnP) activities. The results of the SEC analysis revealed that the mechanism of HA removal by WRF involves degradation of large HA molecules to smaller molecules, conversion of HA to fulvic acid-like molecules and also biosorption of HA by fungal mycelia. The effect of HS on the growth of WRF was investigated and results showed that the inhibition or stimulation of growth differs among the fungal strains.

White rot fungi and advanced combined biotechnology with nanomaterials: promising tools for endocrine-disrupting compounds biotransformation

Endocrine-disrupting compounds (EDCs) can interfere with endocrine systems and bio-accumulate through the food chain and even decrease biodiversity in contaminated areas. This review discusses a critical overview of recent research progress in the biotransformation of EDCs (including polychlorinated biphenyl and nonylphenol, and suspected EDCs such as heavy metals and sulfonamide antibiotics) by white rot fungi (WRF) based on techniques with an emphasis on summarizing and analyzing fungal molecular, metabolic and genetic mechanisms. Not only intracellular metabolism which seems to perform essential roles in the ability of WRF to transform EDCs, but also advanced applications are deeply discussed. This review mainly reveals the removal pathway of heavy metal and antibiotic pollutants because the single pollution almost did not exist in a real environment while the combined pollution has become more serious and close to people's life. The trends in WRF technology and its related advanced applications which use the combined technology, including biocatalysis of WRF and adsorption of nanomaterials, to degrade EDCs have also been introduced. Furthermore, challenges and future research needs EDCs biotransformation by WRF are also discussed. This research, referring to metabolic mechanisms and the combined technology of WRF with nanomaterials, undoubtedly contributes to the applications of biotechnology. This review will be of great benefit to an understanding of the trends in biotechnology for the removal of EDCs.

Enhanced simultaneous saccharification and fermentation of pretreated beech wood by in situ treatment with the white rot fungus Irpex lacteus in a membrane aerated biofilm reactor

The aim of the present study was to investigate the combination of steam pretreatment and biological treatment with lignin degrading fungal strains in order to enable efficient bioprocessing of beech wood to ethanol. In a sequential process of steam and fungal pretreatment followed by enzymatic hydrolysis, Irpex lacteus almost doubled the glucose yield for mildly pretreated beech wood, but could not improve yields for more severely pretreated substrates. However, when simultaneous saccharification and fermentation is combined with in situ I. lacteus treatment, which is enabled by the application of a membrane aerated biofilm reactor, ethanol yields of optimally steam pretreated beech could be improved from 65 to 80%. Generally, in situ fungal treatment during bioprocessing of lignocellulose is an interesting method to harness the versatile abilities of white rot fungi.

Applications of white rot fungi in bioremediation with nanoparticles and biosynthesis of metallic nanoparticles

White rot fungi (WRF) are important environmental microorganisms that have been widely applied in many fields. To our knowledge, the application performance of WRF in bioremediation can be greatly improved by the combination with nanotechnology. And the preparation of metallic nanoparticles using WRF is an emerging biosynthesis approach. Understanding the interrelation of WRF and nanoparticles is important to further expand their applications. Thus, this mini-review summarizes the currently related reports mainly from the two different point of views. We highlight that nanoparticles as supports or synergistic agents can enhance the stability and bioremediation performance of WRF in wastewater treatment and the biosynthesis process and conditions of several important metallic nanoparticles by WRF. Furthermore, the potential toxicity of nanoparticles on WRF and challenges encountered are also discussed. Herein, we deem that this mini-review will strengthen the basic knowledge and provide valuable insight for the applications of WRF and nanoparticles.

Pilot-scale bioconversion of rice and sunflower agro-residues into medicinal mushrooms and laccase enzymes through solid-state fermentation with Ganoderma lucidum

Solid-state fermentation was evaluated at the pilot-scale for the bioconversion and valorization of rice husks and straw (RSH), or sunflower seed hulls (SSH), into medicinal mushrooms and crude extracts, with laccase activity. The average mushroom yield was 56kg dry weight per ton of agro-residues. Laccase activity in crude aqueous extracts showed its maximum value of 10,927Ukg^-1 in RSH (day 10, Exudate phase) and 16,442Ukg^-1 in SSH (day 5, Full colonization phase), the activity at the Residual substrate phase being 511Ukg^-1 in RSH and 803Ukg^-1 in SSH, respectively. Crude extracts obtained with various protocols revealed differences in the extraction yields. Lyophilization followed by storage at 4°C allowed the preservation of laccase activity for more than one month. It is proposed that standard mushroom farms could increase their profits by obtaining laccase as a byproduct during the gaps in mycelium running.

Single-step, single-organism bioethanol production and bioconversion of lignocellulose waste materials by phlebioid fungal species

Ethanol production from non-pretreated lignocellulose was carried out in a consolidated bioprocess with wood-decay fungi of phlebioid Polyporales. Ethanol production was attempted on glucose, spruce wood sawdust and waste core board. Substantial quantities of ethanol were achieved, and isolate Phlebia radiata 0043 produced 5.9g/L of ethanol reaching the yield of 10.4% ethanol from core board lignocellulose substrate. Acidic initial culture conditions (pH 3) induced ethanol fermentation compared to the more neutral environment. Together with bioethanol, the fungi were able to produce organic acids such as oxalate and fumarate, thus broadening their capacity and applicability as efficient organisms to be utilized for bioconversion of various lignocelluloses. In conclusion, fungi of Phlebia grow on, convert and saccharify solid lignocellulose waste materials without pre-treatments resulting in accumulation of ethanol and organic acids. These findings will aid in applying fungal biotechnology for production of biofuels and biocompounds.

Bioremoval of humic acid from water by white rot fungi: exploring the removal mechanisms

Twelve white rot fungi (WRF) strains were screened on agar plates for their ability to bleach humic acid (HA). Four fungal strains were selected and tested in liquid media for removal of HA. Bioremediation was investigated by HA color removal and changes in the concentration and molecular size distribution of HA by size exclusion chromatography. Trametes versicolor and Phanerochaete chrysosporium showed the highest HA removal efficiency, reaching about 80%. Laccase and manganese peroxidase were measured as extracellular enzymes and their relation to the HA removal by WRF was investigated. Results indicated that nitrogen limitation could enhance the WRF extracellular enzyme activity, but did not necessarily increase the HA removal by WRF. The mechanism of bioremediation by WRF was shown to involve biosorption of HA by fungal biomass and degradation of HA to smaller molecules. Also, contradicting previous reports, it was shown that the decolorization of HA by WRF could not necessarily be interpreted as degradation of HA. Biosorption experiments revealed that HA removal by fungal biomass is dependent not only on the amount of biomass as the sorbent, but also on the fungal species. The involvement of cytochrome P450 (CYP) enzymes was confirmed by comparing the HA removal capability of fungi with and without the presence of a CYP inhibitor. The ability of purified laccase from WRF to solely degrade HA was proven and the importance of mediators was also demonstrated.

Use of Swine Wastewater as Alternative Substrate for Mycelial Bioconversion of White Rot Fungi

Seven white rot fungal species were tested for growth as mycelia using swine wastewater (SW), an agro-waste with tremendous environmental footprint, as the sole nutrient source. The SW contained high concentrations of carbon and nitrogen components, which could support nutritional requirements for mycelial growth. Out of the seven species, Pleurotus ostreatus and Hericium erinaceus were successfully cultivated on the SW medium using solid-state fermentation. Response surface methodology was employed to determine the combination of pH, temperature (T), and substrate concentration (C) that maximizes mycelial growth rate (Kr) for the two species. The optimum condition was estimated as pH = 5.8, T = 28.8 °C, and C = 11.2 g chemical oxygen demand (COD)/L for P. ostreatus to yield Kr of 11.0 mm/day, whereas the greatest Kr (3.1 mm/day) was anticipated at pH = 4.6, T = 25.5 °C, and C = 11.9 g COD/L for H. erinaceus. These Kr values were comparable to growth rates obtained using other substrates in the literature. These results demonstrate that SW can be used as an effective substrate for mycelial cultivation of the two white rot fungal species, suggesting an alternative method to manage SW with the production of potentially valuable biomass.