White Rot Fungus Irpex Lacteus Research Articles

Medium-Temperature Pyrolysis of Corn Stover Improved by Biopretreatment with White-rot Fungi

This work investigated the ability of biopretreatment with different white-rot fungi to improve the medium-temperature pyrolysis of biomass. It was found that biopretreatment can significantly increase the production of phenols and glucopyranoside up to 2.82 and 2.94 fold, respectively. Biopretreatment can also decrease the content of carbon dioxide, propanol, and propanone, making the pyrolysis more efficient and product-oriented. Moreover, distinct bio-deconstruction mechanisms can result in different pyrolysis products. By deconstructing cellulose and modifying lignin with a minimum of demethoxyation, white-rot fungus Irpex lacteus CD2 can improve the production of acetaldehyde (up to 6.72%) and methoxyl substitutes such as dimethoxyphenyl (up to 21.59 folds). By decomposing carbohydrates, carbonxyl, and methoxyl groups, white-rot fungi Pleurotus ostreatus BP2 and Echinodontium taxodii 2538 can increase the production of D-allose (up to 3.09%) and formic acid (up to 6.98%), while decreasing the methoxyl substitutes such as 2-methoxy-4-vinylphenol (up to 70.08%).

Fermentation of Biologically Pretreated Wheat Straw for Ethanol Production: Comparison of Fermentative Microorganisms and Process Configurations

The pretreatment of lignocellulosic biomass with white-rot fungi to produce bioethanol is an environmentally friendly alternative to the commonly used physico-chemical processes. After biological pretreatment, a solid substrate composed of cellulose, hemicellulose and lignin, the two latter with a composition lower than that of the initial substrate, is obtained. In this study, six microorganisms and four process configurations were utilised to ferment a hydrolysate obtained from wheat straw pretreated with the white-rot fungus Irpex lacteus. To enhance total sugars utilisation, five of these microorganisms are able to metabolise, in addition to glucose, most of the pentoses obtained after the hydrolysis of wheat straw by the application of a mixture of hemicellulolytic and cellulolytic enzymes. The highest overall ethanol yield was obtained with the yeast Pachysolen tannophilus. Its application in combination with the best process configuration yielded 163 mg ethanol per gram of raw wheat straw, which was between 23 and 35 % greater than the yields typically obtained with a conventional bioethanol process, in which wheat straw is pretreated using steam explosion and fermented with the yeast Saccharomyces cerevisiae.

Biological Pretreatment under Non-sterile Conditions for Enzymatic Hydrolysis of Corn Stover

Pretreatment with white-rot fungi can effectively remove lignin and decompose the structure of biomass to enhance subsequent enzymatic hydrolysis. This study developed a novel fungal pretreatment of biomass, which was operated under non-sterile conditions. The white-rot fungus Irpex lacteus colonized stably on the non-sterile substrates and effectively degraded lignin. After non-sterile fungal pretreatment for 42 days, lignin was degraded by 43.8%. The maximum saccharification efficiency was 7-fold higher after enzymatic hydrolysis compared to that of raw corn stover. Furthermore, the production of ethanol from corn stover improved. During non-sterile biological pretreatment, several microorganisms coexisted with Irpex lacteus, and the microbial community generated abundant by-products that greatly improved the efficiency of enzymatic hydrolysis. Non-sterile fungal pretreatment presents a feasible and promising technology for the production of biofuels by integrating on-farm wet storage systems. Moreover, it provides a low-cost bioconversion process and a stable, secure, and environmentally friendly energy supply.

Improving the conversion of biomass in catalytic fast pyrolysis via white-rot fungal pretreatment

This study investigated the effect of white-rot fungal pretreatment on corn stover conversion in catalytic fast pyrolysis (CFP). Corn stover pretreated by white-rot fungus Irpex lacteus CD2 was fast pyrolyzed alone (non-CFP) and with ZSM-5 zeolite (CFP) in a semi-batch pyroprobe reactor. The fungal pretreatment considerably increased the volatile product yields (predominantly oxygenated compounds) in non-CFP, indicating that fungal pretreatment enhances the corn stover conversion in fast pyrolysis. In the presence of ZSM-5 zeolite, these oxygenated volatiles were further catalytically converted to aromatic hydrocarbons, whose yield increased from 10.03wt.% for the untreated corn stover to 11.49wt.% for the pretreated sample. In contrast, the coke yield decreased from 14.29 to 11.93wt.% in CFP following the fungal pretreatment. These results indicate that fungal pretreatment can enhance the production of valuable aromatics and decrease the amount of undesired coke, and thus has a beneficial effect on biomass conversion in CFP.

Enhanced Saccharification of Biologically Pretreated Wheat Straw for Ethanol Production

The biological pretreatment of lignocellulosic biomass with white-rot fungi for the production of bioethanol is an alternative to the most used physico-chemical processes. After biological treatment, a solid composed of cellulose, hemicellulose, and lignin-this latter is with a composition lower than that found in the initial substrate-is obtained. On the contrary, after applying physico-chemical methods, most of the hemicellulose fraction is solubilized, while cellulose and lignin fractions remain in the solid. The optimization of the combination of cellulases and hemicellulases required to saccharify wheat straw pretreated with the white-rot fungus Irpex lacteus was carried out in this work. The application of the optimal dosage made possible the increase of the sugar yield from 33 to 54%, and at the same time the reduction of the quantity of enzymatic mixture in 40%, with respect to the initial dosage. The application of a pre-hydrolysis step with xylanases was also studied.

Biodecolorization and biodegradation of reactive Levafix Blue E-RA granulate dye by the white rot fungus Irpex lacteus

The treatment of effluents from textile industry with microorganisms, especially bacteria and fungi, has recently gained attention. The present study was conducted using white rot fungi Irpex lacteus, Trametes hirsuta, Trametes sp., and Lentinula edodes for the decolorization of reactive textile Levafix Blue E-RA granulate dye. I. lacteus resulted in the best decolorization and degradation of the dye within four days. Therefore, more detailed studies were carried out using I. lacteus. The decolorization was evaluated at various concentration, pH values, and temperatures. The activities of laccase, manganese peroxidase, and lignin peroxidase enzymes were estimated to reveal the roles of enzymes in decolorization. The colorless nature of the fungal cells revealed that decolorization occurred through degradation, and confirmed by analysis of the metabolites by UV–visible spectroscopy and High Performance Liquid Chromatography after decolorization. The metabolites were identified by Gas Chromatography–Mass Spectrometry, and functional group analysis was performed by Fourier Transform Infrared Spectroscopy. The degraded dye metabolites were assessed for phytotoxicity using Vigna radiata and Brassica juncea, which demonstrated nontoxic nature of the metabolites formed after degradation of dye.

Degradation of Alkylphenols by White Rot Fungus Irpex lacteus and Its Manganese Peroxidase

Alkylphenols are common endocrine disrupters that are produced from the degradation of widely used surfactants. Since they cause various harmful effects on aquatic life and in humans, they should be removed from the environments being contaminated. White rot fungus Irpex lacteus can completely degrade 100 mg/L of octylphenol, nonylphenol, and phenylphenol during 1 day of incubation in the complex YMG medium, which was the highest degrading capability among nine strains of white rot fungi tested. In the N-limited Kirk's basal salts medium, I. lacteus could degrade almost 100 % of 100 mg/L octylphenol and nonylphenol in 1 h, and exhibited a high activity of manganese peroxidase (MnP; 1,790 U/L). MnP of I. lacteus was purified by ion exchange chromatography, and this degraded 99 % of 50 mg/L octylphenol and removed 80 % of estrogenic activity in 2 hours. In addition, the purified MnP (10 U/mL) degraded over 90 % of 50 mg/L nonylphenol in 1 h.

Hydrodynamics of a Laboratory Scale Rotating Biological Contactor and Its Application for Decolorization of Textile Dyes by White Rot Fungus Irpex Lacteus

Textile industries produce huge amounts of colored wastewaters contaminated with various textile dyes. These waters represent serious environmental problem as common wastewater treatment procedures are not efficient to degrade the dyes. Therefore, new ways of textile wastewater treatment are looked for in order to tackle this environmental problem. An application of the white rot fungus Irpex lacteus, that is known to degrade many recalcitrant pollutants, seems to be one of possible options for the waste water decolorization. A laboratory scale Rotating Biological Contactor was constructed to perform the decolorization tests. The reactor vas equipped with 12 flat circular discs (o = 0.13 m, ?? = 0.01 m) mounted on a common shaft. The discs were made of the Filtren TM30 reticulated polyether foam. Volume of the liquid in the reactor was 1.5 dm3. Residence time distributions of the liquid phase in the reactor were measured to obtain hydrodynamic characteristics. The measurements were carried out at various liquid volumetric flow rates and at different rotational speeds of the discs uncovered with the biomass. The measured data were used to determine the liquid mean residence time and parameters of the gamma distribution model and of the model of the stirred tanks in series with the back-flow. The residence time distributions were also measured after 36 days of the reactor operation, i.e., with the discs covered with the Irpex lacteus mycelium biofilm. The flow behavior of the reactor without the fungus was close to the ideally stirred reactor behavior. The presence of the biomass in the reactor brought about deviations from the ideal mixing. Continuous decolorization experiments with the textile dye Remazol Brilliant Blue R and with a sample of an industrial textile waste water were performed. In the course of the experiments, activities of the enzymes involved in the dye decolorization, i.e., laccase, manganese-dependent peroxidase and lignin peroxidase were determined in the outlet stream of the reactor. The inlet and outlet concentrations of glucose were also measured. The results of the decolorization experiments will be presented and mutually compared and effects of hydrodynamic parameters on decolorization will be discussed.

Rotating Drum Biological Contactor and its Application for Textile Dyes Decolorization

A laboratory-scale rotating drum biological contactor (RDBC) with immobilized white rot fungus Irpex lacteus was used to decolorize synthetic wastewaters containing the azo dye Reactive Orange 16 (RO16) and the anthraquinone dye Remazol Brilliant Blue R (RBBR). Two particulate drum packings were used to immobilize the fungus: the AL-Schwimmbett Medium 100L that appeared not to be convenient, because of a low adhesion of the fungal mycelium to the particles, and the oak wood cylinders that supported formation of a thin layer of the fungal biofilm on the surface of the particles resulting to faster degradation of the dyes in comparison with the AL-Schwimmbett Medium 100L particles. In batch decolorization experiments at the initial dyes concentration of 100 mg dm-3 it took from 4 to 5 hours for the RBBR and 21 hours for RO16 to get 85% decolorization. In the continuous decolorization experiment at high inlet mass flow rate (0.5 mg min-1) of the RBBR dye the degree of decolorization achieved was just 20%. Activities of the enzymes manganese-dependent peroxidase, lignin peroxidase and laccase were also monitored during experiments.

Comparative Studies on Thermochemical Characterization of Corn Stover Pretreated by White-Rot and Brown-Rot Fungi

The effects of white-rot and brown-rot fungal pretreatment on the chemical composition and thermochemical conversion of corn stover were investigated. Fungus-pretreated corn stover was analyzed by Fourier transform infrared spectroscopy and X-ray diffraction analysis to characterize the changes in chemical composition. Differences in thermochemical conversion of corn stover after fungal pretreatment were investigated using thermogravimetric and pyrolysis analysis. The results indicated that the white-rot fungus Irpex lacteus CD2 has great lignin-degrading ability, whereas the brown-rot fungus Fomitopsis sp. IMER2 preferentially degrades the amorphous regions of the cellulose. The biopretreatment favors thermal decomposition of corn stover. The weight loss of IMER2-treated acid detergent fiber became greater, and the oil yield increased from 32.7 to 50.8%. After CD2 biopretreatment, 58% weight loss of acid detergent lignin was achieved and the oil yield increased from 16.8 to 26.8%.

Mathematical modeling of wastewater decolorization in a trickle-bed bioreactor

This work focuses on mathematical modeling of removal of organic dyes from textile industry waste waters by a white-rot fungus Irpex lacteus in a trickle-bed bioreactor. We developed a mathematical model of biomass and decolorization process dynamics. The model comprises mass balances of glucose and the dye in a fungal biofilm and a liquid film. The biofilm is modeled using a spatially two-dimensional domain. The liquid film is considered as homogeneous in the direction normal to the biofilm surface. The biomass growth, decay and the erosion of the biofilm are taken into account. Using experimental data, we identified values of key model parameters: the dye degradation rate constant, biofilm corrugation factor and liquid velocity. Considering the dye degradation rate constant 1×10⁻⁵ kg m⁻³ s⁻¹, we found optimal values of the corrugation factor 0.853 and 0.59 and values of the liquid velocity 5.23×10⁻³ m s⁻¹ and 6.2×10⁻³ m s⁻¹ at initial dye concentrations 0.09433 kg m⁻³ and 0.05284 kg m⁻³, respectively. A good agreement between the simulated and experimental data using estimated values of the model parameters was achieved. The model can be used to simulate the performance of laboratory scale trickle-bed bioreactor operated in a batch regime or to estimate values of principal parameters of the bioreactor system.

Biological Pretreatment of Corn Stover by Irpex lacteus for Enzymatic Hydrolysis

The feasibility of biological pretreatment for subsequent saccharification largely depends upon an effective pretreatment system. A significant enhancement of saccharification was discovered with corn stover pretreated by white rot fungus Irpex lacteus CD2. The highest saccharification ratio reached 66.4%, which was significantly higher than what was reported. Hemicellulose was first destroyed in the process and then lignin. Lignin and hemicellulose were selectively degraded over cellulose, respectively, resulting in increased crystallinity. Enhanced saccharification and the fluctuation in crystallinity together indicated the destruction of the cellulose crystalline structure. Additionally, further studies revealed the disruption of the cell wall and the vital increase of large pores in the pretreated samples, which might be caused by the selective degradation of amorphous components and fungal penetration. Results suggest that I. lacteus has a more efficient degradation system than other reported white rot fungi and can be further explored as an alternative to the existing thermochemical processes.

Isolation and characterization of novel pI 4.8 MnP isoenzyme from white-rot fungus Irpex lacteus

Growth of Irpex lacteus on polyurethane solid support led to secretion of various manganese-dependent peroxidase (MnP) isoenzymes with pI in the range of 3.8–6.7. The highest MnP activity was obtained at 8.9 mmol l −1 Mn 2+ when predominantly a pI 4.8 isoenzyme was produced. Optimization of anion exchange chromatography (Mono Q) allowed the separation of MnP isoenzymes and collection of extensive sequence information by tandem LC–MS. The pI 4.8 isoenzyme was purified 109-fold (6% activity yield) by ion exchange chromatography, its specific activity of Mn 2+ oxidation was 2800 nkat mg −1, molecular mass 37 kDa and pH optimum 5. The other properties were: respective half-lives (pH 4.5) of 575, 325 and 7 min at 40, 50 and 60 °C, K m values 46.7; 9.5; 21.4 μmol l −1 and k cat values 69.0; 64.2; 15.7 s −1 for Mn 2+, H 2O 2 and DMP with Mn 2+, respectively. The pI 4.8 isoenzyme was shown to be a true MnP affecting secondary substrates via the oxidation of Mn 2+. Its biochemical properties and production by I. lacteus make the enzyme a candidate for biotechnological applications.

Structure alteration of lignin in corn stover degraded by white-rot fungus Irpex lacteus CD2

Lignin was isolated from corn stover degraded by Irpex lacteus CD2 to better understand how white-rot fungi decomposed corn stover lignin, and the structure alterations were analyzed by elemental analysis, FTIR, 13C NMR, 1H NMR, and UV spectra. These investigations illustrate significant structure differences between degraded and undegraded corn stover lignin that, in I. lacteus CD2 degraded lignin, aliphatic hydroxyl groups decreased remarkably, while conjugated carbonyl groups increased obviously. Moreover, the content of etherified guaiacyl units enhanced nearly twice, with the content of etherified syringyl units declining simultaneously. The increasing content of CH 3 in ArOCH 3 and the decreasing contents of guaiacyl and syringyl units were also observed in the degraded lignin, supposed to be the result of aromatic ring cleavage. By isolating lignin from degraded corn stover, the research demonstrates lignin structure differences contributed by white-rot fungus I. lacteus CD2 more profound and clear than investigations carried out by researching on lignin model compounds.

Lignocellulose degradation and enzyme production by Irpex lacteus CD2 during solid-state fermentation of corn stover

The white rot fungus Irpex lacteus CD2 was incubated on corn stover under solid-state fermentation conditions for different durations, from 5 days up to 120 days. Lignocellulose component loss, enzyme production and Fe3+-reducing activity were studied. The average weight loss ranged from 1.7% to 60.5% during the period of 5-120 days. In contrast to lignin, hemicellulose and cellulose were degraded during the initial time period. After 15 days, 63.0% of hemicellulose was degraded. Cellulose was degraded the most during the first 10 days, and 17.2% was degraded after 10 days. Lignin was significantly degraded and modified, with acid insoluble lignin loss being nearly 80% after 60 days. That weight loss, which was lower than the total component loss, indicated that not all of the lost lignocellulose was converted to carbon dioxide and water, which was indicated by the increase in soluble reducing sugars and acid soluble lignin. Filter paper activity, which corresponds to total cellulase activity, peaked at day 5 and remained at a high level from 40 to 60 days. High hemicellulase activity appeared after 30 days. No ligninases activity was detected during the incipient stage of lignin removal and only low lignin peroxidase activity was detected after 25 days. Apparently, neither of the enzymatic peaks coincided well with the highest amount of component loss. Fe3+-reducing activity could be detected during all the decay periods, which might play an important role in lignin biodegradation by I. lacteus CD2.

Biodegradation of 2,4,6-Trinitrotoluene by White-Rot Fungus Irpex lacteus

White-rot fungus Irpex lacteus degraded TNT significantly in proportion to the culture time. After 48 h incubation, about 95% of TNT was degraded. Two reduced metabolites were identified as 4-amino-2,6-dinitrotoluene (4-ADNT) and 2-amino-4,6-dinitrotoluene (2-ADNT) which was further degraded.

Iron and calcium translocation from pure gypsum and iron-amended gypsum by two brown rot fungi and a white rot fungus

Abstract Wood-degrading fungi commonly grow in contact with calcium (Ca)-containing building materials and may import Ca and iron (Fe) from soil into forest woody debris. For brown rot fungi, imported Ca2+ may neutralize oxalate, while Fe3+ may facilitate Fenton-based degradation mechanisms. We previously demonstrated, in two independent trials, that degradation of spruce by wood-degrading fungi was not promoted when Ca or Fe were imported from gypsum or metallic Fe, respectively. Here, we tested pine wood with lower endogenous Ca than the spruce blocks used in prior experiments, and included a pure gypsum treatment and one amended with 1% with FeSO4. Electron microscopy with microanalysis verified that brown rot fungi Serpula himantioides and Gloeophyllum trabeum and the white rot fungus Irpex lacteus grew on gypsum and produced iron-free Ca-oxalate crystals away from the gypsum surface. Wood cation analysis verified significant Fe import by both brown rot isolates in Fe-containing treatments. Wood degradation was highest in Fe-gypsum-containing treatments for all three fungi, although only wood degraded by I. lacteus had significant Ca import. We suggest that Fe impurities may not exacerbate brown rot, and that both brown and white rot fungi may utilize Ca-containing materials.

Mobilizing agents enhance fungal degradation of polycyclic aromatic hydrocarbons and affect diversity of indigenous bacteria in soil

The impact of several mobilizing agents (MAs) (i.e., soybean oil, Tween-20, Tween-80, olive-oil mill wastewaters, and randomly methylated beta-cyclodextrins) on the degradation performances of the white-rot fungi Irpex lacteus and Pleurotus ostreatus was comparatively assessed in a soil spiked with a mixture of seven polycyclic aromatic hydrocarbons (PAHs). Among the different MAs, soybean oil best supported the growth of both fungi that was twice that observed in soil in the absence of MAs. In addition, soybean oil positively affected PAH degradation by both fungi. In this case, the total weight of organic contaminants (TWOC) was lower than that in the absence of MAs (57.7 vs. 201.3 and 26.3 vs. 160.4 mg kg(-1) with I. lacteus and P. ostreatus, respectively). On the other hand, the number of cultivable heterotrophic bacteria was significantly lower in the soil with soybean oil augmented with either one of the two fungi (5.21 vs. 8.71 and 0.22 vs. 0.51 x 10(7) CFU g(-1) soil with I. lacteus and P. ostreatus, respectively). The effect of soybean oil was confirmed by denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA genes that showed a general decrease in biodiversity. The impact of the other MAs on bacterial diversity was either slightly negative or positive in incubation controls. Both richness and Shannon-Weaver index decreased upon treatment with P. ostreatus. Moreover, with this fungus the composition of the indigenous bacteria was not significantly affected by the type of MA used. By contrast, both indices increased in soil with I. lacteus in the presence of randomly methylated beta-cyclodextrins (39 vs. 33 and 1.43 vs. 1.26, respectively) and soybean oil (19 vs. 5 and 1.01 vs. 0.65, respectively).

Implication of mycelium-associated laccase from Irpex lacteus in the decolorization of synthetic dyes

The white rot fungus Irpex lacteus is able to decolorize such synthetic dyes as Reactive Orange 16 and Remazol Brilliant Blue R. Here, we demonstrate that this type of dye decolorization is mainly related to a laccase-like enzyme activity associated with fungal mycelium. In its bound form, the enzyme detected showed a pH optimum of 3.0 for the oxidation of ABTS, DMP and guaiacol, and a pH of 7.0 for syringaldazine. The highest enzymatic activity was obtained with ABTS as substrate. Enzyme activity was fully inhibited with 50 mM NaN 3. Depending on the chemical structure of dyes, redox mediators had a positive effect on the dye decolorization by fungal mycelium. Enzyme isolated from fungal mycelium was able to decolorize synthetic dyes in vitro.

Purification of a new manganese peroxidase of the white-rot fungus Irpex lacteus, and degradation of polycyclic aromatic hydrocarbons by the enzyme

The white-rot fungus Irpex lacteus has been reported to be an efficient degrader of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and pentachlorophenol. The fungus produces ligninolytic enzymes laccase, lignin peroxidase and manganese peroxidase (MnP), the latter being the major one produced. MnP was purified using anion exchange and size exclusion chromatography. SDS–PAGE showed the purified MnP to be a monomeric protein of 37 kDa (37.5 kDa using MALDI-TOF) with an isoelectric point at 3.55. The pH optimum was relatively broad, from 4.0 to 7.0 with a peak at pH 5.5. Kinetic constants K m were 8 μM for H 2O 2 and 12 or 31 μM for Mn 2+ depending on the substrate. The enzyme did not perform oxidation in the absence of H 2O 2 or Mn 2+. MnP was active at 5–70 °C with an optimum between 50–60 °C. At temperatures above 65 °C the enzyme rapidly lost activity. Degradation of four representatives of PAHs (phenanthrene, anthracene, fluoranthene, and pyrene) was tested and the enzyme showed the ability to degrade them in vitro. Major degradation products of anthracene were identified. The results confirm the role of MnP in PAH degradation by I. lacteus, including cleavage of the aromatic ring.