Ligninolytic Enzyme Activities Research Articles

Fungal Bioremediation of the β-Lactam Antibiotic Ampicillin under Laccase-Induced Conditions.

Due to widespread overuse, pharmaceutical compounds, such as antibiotics, are becoming increasingly prevalent in greater concentrations in aquatic ecosystems. In this study, we investigated the capacity of the white-rot fungus, Coriolopsis gallica (a high-laccase-producing fungus), to biodegrade ampicillin under different cultivation conditions. The biodegradation of the antibiotic was confirmed using high-performance liquid chromatography, and its antibacterial activity was evaluated using the bacterial growth inhibition agar well diffusion method, with Escherichia coli as an ampicillin-sensitive test strain. C. gallica successfully eliminated ampicillin (50 mg L-1) after 6 days of incubation in a liquid medium. The best results were achieved with a 9-day-old fungal culture, which treated a high concentration (500 mg L-1) of ampicillin within 3 days. This higher antibiotic removal rate was concomitant with the maximum laccase production in the culture supernatant. Meanwhile, four consecutive doses of 500 mg L-1 of ampicillin were removed by the same fungal culture within 24 days. After that, the fungus failed to remove the antibiotic. The measurement of the ligninolytic enzyme activity showed that C. gallica laccase might participate in the bioremediation of ampicillin.

Temporal dynamics of lignin degradation in Quercus acutissima sawdust during Ganoderma lucidum cultivation

Despite a fair amount of lignin conversion during mycelial growth, previous structural analyses have not yet revealed how lignin changes continuously and what the relationship is between lignin and ligninolytic enzymes. To clarify these aspects, Quercus acutissima sawdust attaching Ganoderma lucidum mycelium collected from different growth stage was subjected to analysis of lignin structure and ligninolytic enzyme activity. Two key periods of lignin degradation are found during the cultivation of G. lucidum: hypha rapid growth period and primordium formation period. In the first stage, laccase activity is associated with the opening of structures such as methoxyls, β-O-4′ substructures and guaiacyl units in lignin, as well as the shortening of lignin chains. Manganese peroxidases and lignin peroxidases are more suitable for degrading short chain lignin. The structure of phenylcoumarans and syringyl changes greatly in the second stage. The results from sawdust attaching mycelium provide new insights to help improve the cultivation substrate formulation of G. lucidum and understand biomass valorization better.

Characterization and removal mechanism of fluoroquinolone-bioremediation by fungus Cladosporium cladosporioides 11 isolated from aquacultural sediments.

Antibiotics have been widely detected in aquatic environments, and fungal biotransformation receives considerable attention for antibiotic bioremediation. Here, a fungus designated Cladosporium cladosporioides 11 (CC11) with effective capacity to biotransform fluoroquinolones was isolated from aquaculture pond sediments. Enrofloxacin (ENR), ciprofloxacin (CIP) and ofloxacin (OFL) were considerably abated by CC11, and the antibacterial activities of the fluoroquinolones reduced significantly after CC11 treatment. Transcriptome analysis showed the removal of ENR, CIP and OFL by CC11 is a process of enzymatic degradation and biosorption which consists well with ligninolytic enzyme activities and sorption experiments under the same conditions. Additionally, CC11 significantly removed ENR in zebrafish culture water and reduced the residue of ENR in zebrafish. All these results evidenced the potential of CC11 as a novel environmentally friendly process for the removal of fluoroquinolones from aqueous systems and reduce fluoroquinolone residues in aquatic organisms.

Lignin bioconversion based on genome mining for ligninolytic genes in Erwinia billingiae QL-Z3

BackgroundBioconversion of plant biomass into biofuels and bio-products produces large amounts of lignin. The aromatic biopolymers need to be degraded before being converted into value-added bio-products. Microbes can be environment-friendly and efficiently degrade lignin. Compared to fungi, bacteria have some advantages in lignin degradation, including broad tolerance to pH, temperature, and oxygen and the toolkit for genetic manipulation.ResultsOur previous study isolated a novel ligninolytic bacterial strain Erwinia billingiae QL-Z3. Under optimized conditions, its rate of lignin degradation was 25.24% at 1.5 g/L lignin as the sole carbon source. Whole genome sequencing revealed 4556 genes in the genome of QL-Z3. Among 4428 protein-coding genes are 139 CAZyme genes, including 54 glycoside hydrolase (GH) and 16 auxiliary activity (AA) genes. In addition, 74 genes encoding extracellular enzymes are potentially involved in lignin degradation. Real-time PCR quantification demonstrated that the expression of potential ligninolytic genes were significantly induced by lignin. 8 knock-out mutants and complementary strains were constructed. Disruption of the gene for ELAC_205 (laccase) as well as EDYP_48 (Dyp-type peroxidase), ESOD_1236 (superoxide dismutase), EDIO_858 (dioxygenase), EMON_3330 (monooxygenase), or EMCAT_3587 (manganese catalase) significantly reduced the lignin-degrading activity of QL-Z3 by 47–69%. Heterologously expressed and purified enzymes further confirmed their role in lignin degradation. Fourier transform infrared spectroscopy (FTIR) results indicated that the lignin structure was damaged, the benzene ring structure and groups of macromolecules were opened, and the chemical bond was broken under the action of six enzymes encoded by genes. The abundant enzymatic metabolic products by EDYP_48, ELAC_205 and ESOD_1236 were systematically analyzed via liquid chromatography–mass spectrometry (LC–MS) analysis, and then provide a speculative pathway for lignin biodegradation. Finally, The activities of ligninolytic enzymes from fermentation supernatant, namely, LiP, MnP and Lac were 367.50 U/L, 839.50 U/L, and 219.00 U/L by orthogonal optimization.ConclusionsOur findings provide that QL-Z3 and its enzymes have the potential for industrial application and hold great promise for the bioconversion of lignin into bioproducts in lignin valorization.

Production of oxidative and hydrolytic enzymes from Pleurotus florida and their implication in mushroom cultivation

One of the most economically viable processes for the bioconversion of many types of lignocellulosic wastes is represented by edible mushroom cultivation. Pleurotus florida is one of the prominent economically cultivated mushrooms with varied abilities to utilize lignocellulose as a growth substrate. Thus, the profile of oxidative and hydrolytic enzymes was measured during the submerged and solid-state fermentation at Punjab Agricultural University, Ludhiana, Punjab during the winter (rabi) season of the year 2020–21. The intracellular activity of laccase (10.23 IU/mg), manganese peroxidase (9.98 IU/mg), cellobiohydrolase (5.46 IU/mg) was best obtained in P. florida on the 14th day. The extracellular activity of laccase (15.43 IU/ml), lignin peroxidase (11.21 IU/ml), endoxylanases (9.22 IU/ml)were found to be highest on the 14th day. P. florida had substantial levels of ligninolytic enzymes during substrate colonization but rapidly diminished during fruit body development. On the other hand, P. florida showed relatively low hydrolase activity during substrate colonization. The activity of these enzymes increased when primordia formed. The hydrolytic activities peaked at the mature fruiting body stage. When mushrooms switched to vegetative development, ligninolytic enzyme activity increased again, while hydrolase activity declined. The yield was found to be 58.78% after the enzymatic treatment of paddy straw. These findings suggest that fluctuations in oxidative and hydrolytic enzyme activities are linked to the growth of the fruiting body and the physiological state of mushroom cultivation.

Deciphering ligninolytic enzymes in the secretome of Pycnoporus sp. and their potential in degradation of 2-chlorophenol.

Chlorophenols and their derivatives are persistent environmental pollutants, posing a threat to terrestrial and aquatic life. The biological approach for eliminating toxic contaminants is an effective, sustainable, and environmental friendly method. In this study, the crude enzymes present in the secretome of white-rot fungus (Pycnoporus sp.) were explored for the degradation of 2-chlorophenol. The activity of ligninolytic enzymes in the secretome was analyzed and characterized for their kinetics and thermodynamic properties. Laccase and manganese peroxidase were prevalent ligninolytic enzymes and exhibited temperature stability in the range of 50-65°C and pH 4-5, respectively. The kinetic parameters Michaelis constant (Km) and turnover number (Kcat) for Lac were 42.54μM and 45s-1 for 2,2'-azino-bis (3-ethylben- zothiazoline-6-sulfonic acid), and 93.56μM and 48s-1 towards 2,6-dimethoxyphenol whereas Km and Kcat for MnP were 2039μM and 294s-1 for guaiacol as substrate. Treatment with the crude enzymes laccase and manganese peroxidase results in the reduction of 2-chlorophenol concentration, confirmed by UV-visible absorption spectra and high-performance liquid chromatography analysis. The detoxification of 2-chlorophenol into less toxic forms was confirmed by the plate toxicity assay. This study demonstrated that crude enzymes produced by Pycnoporus sp. could potentially minimize the toxicity of phenolic compounds in a sustainable way.

Mycoremediation of pretilachlor and its metabolite by Aspergillus ficuum

Pretilachlor is one of the widely used chloroacetamide herbicides in Asian countries to control weeds in the rice field. The extensive use of herbicides has caused major concern among scientists throughout the world. Therefore, it is essential to develop an efficient method for the remediation of pretilachlor and its harmful by-products from contaminated surfaces. Mycoremediation is known to play a key role in the removal of various environmental contaminants. Hence, in the present study, strain AJN2 Aspergillus ficuum was isolated from a paddy field that was in continuous exposure to pretilachlor for over a decade. The degradation studies showed that the strain was efficiently able to degrade 73% of pretilachlor in an aqueous medium within 15 days of incubation and 70% of its major metabolite PME (2-methyl-6-ethylalanine). The GC/MS profile revealed the formation of aldehyde as the end product of degradation which was confirmed through the infrared fingerprint of the degradation sample. The ligninolytic enzyme activity studies showed that the lignin peroxidase enzyme system could be responsible for the degradation of pretilachlor and its major metabolite. The results highlight that the strain AJN2 A. ficuum could be a potential strain for the bioremediation of pretilachlor from the contaminated areas.

Effect of different water contents in the substrate on cultivation of Pleurotus ostreatus Jacq. P. Kumm

ABSTRACT Pleurotus ostreatus is a widely cultivated and investigated mushroom for its economical and ecological values and medicinal properties. P. ostreatus can be cultivated on different lignocellulosic substrates (oak sawdust, wheat straw, corn cobs and many more). Optimal growth is influenced not only by the composition of the substrate but also by the amount of water in it. In our study, P. ostreatus was cultivated on wheat straw pellets with different water contents (60%, 65%, 70% and 75%). Mycelium growth, biological efficiency (BE), moisture of substrate, pH, enzymatic activities and relationships were the parameters that were evaluated. Based on the results, the optimum initial substrate water content for mycelial growth and BE of the substrate ranged between 65% and 75%. On the other hand, the highest enzymatic activities of hydrolytic and ligninolytic enzymes (Mn-dependent peroxidase, 1,4-β-glucosidase and cellobiohydrolase) were determined for substrates with 75% of water content.

Bacterial assisted phytoremediation of heavy metals and organic pollutants by Cannabis sativa as accumulator plants growing on distillery sludge for ecorestoration of polluted site

The aim of the study is to explore the potential rhizospheric bacterial communities associated with Cannabis sativa L. (Cannabis); growing on the complex pollutant-rich distillery sludge. Seven bacterial species were isolated, among which four potential bacterial species were characterized based on the 16s rRNA sequencing from the rhizosphere sludge of C. sativa; they are Bacillus thuringiensis (MW887525), Bacillus cereus (MW887524), Achromobacter denitrificans (MW886333), Bacillus subtilis (MW886231). The isolated bacteria showed PGPR attributes and potential for ligninolytic enzyme activity. Further, to correlate these bacteria with organic pollutants of sludge, the GC-MS analysis of fresh disposed distillery sludge and after growth of 30 and 60 days C. sativa was also analysed, which showed the conversion and disappearance of compounds by the activity of rhizospheric bacterial communities. Additionally, C. sativa showed a higher metal accumulation pattern of Fe (801.81 ± 0.123)> Cu (275.086 ± 0.069)> Zn (162.15 ± 0.085)> Mn (63.92 ± 0.093)> Pb (28.619 ± 0.192)> Ni (5.02 ± 0.078)> Cd (2.53 ± 0.085)> Cr (1.87 ± 0.079) mg kg −1 in their shoot, root followed by leaf. The plant also showed BCF >1 and TF > 1 for most of the metals. Thus, this showed the phytoextraction properties of C. sativa from distillery sludge polluted sites. The findings of this study will enable to understand the functional role of rhizospheric bacterial community for the detoxification and degradation of complex organometallic waste, and will thus aid in the development of adequate phytoremediation techniques for the eco-restoration of polluted industrial sites for sustainable development.

Efecto del tamaño de partícula, aireación y altura del sustrato sobre la producción de enzimas lignocelulolíticas producidas por Trametes polyzona HHM001 crecido sobre residuos de hojas de maíz

The objective of the work was to evaluate the production of lignocllulolytic enzymes produced by Trametes polyzona HHM001 during its growth on corn leaf residues. Two particle sizes (PS) (PS8 and PS12), two levels of aeration (1 vvm and 0 vvm), as well as the height of the substrate in the production of lignocellulolytic enzymes were tested. The enzymatic activities of Laccase (Lcc), Lignin peroxidase (LiP), and Manganese peroxidase (MnP) were favored under aerated conditions (1 vvm). The enzymatic activity of Lcc was the most favored, with 80 Activity Units (AU)/mL, compared to the culture without aeration, in which 40 AU/mL was obtained. The production of xylanases (Xyl) and cellulases (Cel) were not influenced by aeration under the tested conditions. The results indicated that the particle size has more effect on enzyme production than the presence or absence of air, with a particle size of 8 where the best levels of enzymatic activity were observed. It was observed that the height of the substrate in the fermentation column strongly affects the activity of ligninolytic enzymes and not of the hydrolytic; at 5 cm, the highest ligninolytic activity was detected, where aeration favors oxidative conditions.

Wheat straw delignification by Djerkandera adusta (Willd.) P. Karst. 1879: The effect on enzymatic hydrolysis

The use of lignocellulosic materials in the production of biofuels and biochemicals holds a huge prospect since wood and agricultural residues represent the most abundant global source of renewable biomass. However, delignification is an inevitable step in lignocellulose pre-treatment rendering the cellulose and hemicellulose more exposed to enzymatic saccharification. The aim of this study was to assess the potential of different Bjerkandera adusta strains to enhance the efficiency of enzymatic saccharification of wheat straw after solid-state culturing. Three white-rot fungal strains of Bjerkandera adusta (Willd.) P. Karst. 1879, (BEOFB1601, BEOFB1602 and BEOFB1603) were used for partial delignification of wheat straw during solid-state cultivation. Activity of ligninolytic enzymes were measured spectrophotometrically while wheat straw residues were used for determination of hemicelluloses, cellulose and lignin contents. Enzymatic hydrolysis of pre-treated wheat straw was conducted using commercial cellulase in loadings of 60 U g-1 of solid substrate. The content of reducing sugars was measured calorimetrically using 1,4-dinitrosalycilic acid. Enzymes predominantly responsible for lignin degradation by tested fungal strains were peroxidases. The highest rate of lignin degradation was noticed in samples pretreated with the strain BEOFB1601 (42.3 ? 3.7%). The highest reducing sugars yield (8.6 ? 0.3 gGE L-1) was achieved after enzymatic saccharification of samples pre-treated with the strain BEOFB1601, as the most selective lignin degrader. The obtained results suggest that fungal culturing as a bio?logical pre-treatment method can be significantly strain specific. A key mechanism which enhances convertibility of carbohydrates is selective lignin degradation of the biomass.

Transforming second-generation ethanol production waste into sustainable enzymatic cosmetic inputs

Agro-industrial residues were used as a successful, cheap and renewable substrate, capable of increasing activity of ligninolytic enzymes for further use in melanin degradation assays to develop inputs for the treatment of skin hyperpigmentation. The analysis of melanin degradation was performed in a quantitative and qualitative way. The enzymatic crude broth extract, rich in laccases , produced by Marasmiellus palmivorus VE111 in medium formulated with lignocellulosic residues of Araucaria angustifolia subjected to hydrolysis and alcoholic fermentation , degraded almost 33% of the melanin content and enzymatic crude broth extract produced by Pycnoporus sanguineus PR_32 degraded 13%, in just 8 h, using vanillin as a mediator. Proton 2D NMR spectra show melanin changes after laccase treatment. This work has provided an insight for the development of ecofriendly, sustainable and innovative cosmetics to deal with skin hyperpigmentation. • By-products from 2nd generation ethanol production act as inducer to laccases activity. • Vanillin can be used as a safe redox mediator for laccase activity in cosmetics. • Laccase from Marasmiellus palmivorus VE111 can degrade melanin. • HSQC 2D NMR data shows changes in melanin after enzymatic treatment.

Evaluating the potential of engineered Trichoderma atroviride and its laccase-mediated system for the efficient bioconversion of 5-hydroxymethylfufural

5-Hydroxymethylfurfural (HMF) is a fermentation inhibitor which is formed during acid-based thermochemical pre-treatment of biomass. The present study involves two approaches for HMF conversion; the first includes screening and identification of fungal strains which produce oxidoreductases for HMF bioconversion, and thereafter evaluating their roles in HMF conversion. Out of the ten fungal strains screened, genetically engineered Trichoderma atroviride (Lac+) showed maximum HMF bioconversion and the activities of ligninolytic enzymes produced were noted. Maximum HMF conversion of 99% was achieved at pH 5.0 and 30 °C when 72 h old 10% inoculum of T. atroviride (Lac+) was utilized for 6 days. Based on the fungal bioconversion of HMF to 2, 5 diformylfuran with 58% yield, laccase was observed to influence the conversion process. Thus, a comparative study was established on HMF conversion by 100 U/mL of commercial laccases and partially purified laccase from T. atroviride (Lac+). In the presence of TEMPO, T. atroviride laccase showed comparable HMF conversion to commercial laccases, which establishes the efficiency of fungi and ligninolytic enzymes in bioconversion of HMF to value-added products.

White rot fungus Calocybe indica: Incredulous factory of lignocellulolytic enzymes and their potential applicability for mushroom cultivation

Abstract Cultivation of specialty mushrooms on lignocellulosic wastes represents one of the most economical organic recycling processes. Compared with other cultivated mushrooms, very little is known about the nature of the lignocellulolytic enzymes produced by the edible fungus Calocybe indica, its enzymatic activity profiles during submerged and solid state fermentation. The intracellular activity of laccase (7.67 U mg−1), manganese peroxidase (7.48 U mg−1), cellobiohydrolase (5.46 U mg−1), and endoxylanase (4.21 U mg−1) was best obtained in C. indica on 14th and 21st day of incubation. The extracellular activity of laccase (11.57 U mL−1), lignin peroxidase (8.45 U mL−1), and endoxylanases (6.22 U mL−1) were found to be highest on the 14th day. Ligninolytic enzyme activity was substantial during substrate colonisation but quickly dropped during fruiting body development. C. indica, on the other hand, showed relatively modest hydrolase activity during substrate colonisation. The activity of hydrolytic enzymes increased dramatically when primordia formed and peaked at the mature fruiting body stage. The yield of the crude enzyme-treated wheat straw utilised for mushroom production was 52.47%. These findings showed that the activities of lignocellulolytic enzymes were regulated in line with developmental phase of growth of C. indica.

Evaluation of Phanerochaete chrysosporium for swine wastewater treatment

The swine slurry is a mixture of manure, urine, and cleaning water from pig livestock farms, characterized by its high chemical oxygen demand (COD) and ammonia concentration. This effluent needs to be treated before being spilled to avoid negative environmental impacts as eutrophication of surface water reservoirs. In this study, an untreated slurry and two pig slurries pre-treated by anaerobic digestion with and without ammonia trapping were treated biologically by Phanerochaete chrysosporium. The effect on the biological treatment of pre-treating the raw slurry by sieving and centrifugation was evaluated. Samples were inoculated with 3 g/L (dry matter) of fungus and incubated at 26 °C during 10 days in a batch reactor. The activity of ligninolytic enzymes (LiP, MnP and Lac), colour, COD, total nitrogen and BOD5 evolution during the treatment were analysed. For undigested slurries, the best results were obtained for sieved slurry, reaching removal efficiencies for soluble COD and colour around 68% and 78%, respectively. For digested effluents, the digestate coming from the reactor with ammonia trapping membrane showed the best results with efficiencies of 38% for soluble COD and 35% for colour. These results provide new insights into the application of this fungus as complementary method to treat swine wastewaters.

Isolation and characterization of a novel thermotolerant alkali lignin-degrading bacterium Aneurinibacillus sp. LD3 and its application in food waste composting

The aim of this study was to isolate thermotolerant alkali lignin-degrading bacteria and to investigate their degradation characteristics and application in food waste composting. Two thermotolerant alkali lignin-degrading bacteria isolates were identified as Bacillus sp. LD2 (LD2) and a novel species Aneurinibacillus sp. LD3 (LD3). Compared with strain LD2, LD3 had a higher alkali lignin degradation rate (61.28%) and ligninolytic enzyme activities, and the maximum lignin peroxidase, laccase, and manganese peroxidase activities were 3117.25, 1484.5, and 1770.75 U L−1, respectively. GC-MS analysis revealed that low-molecular-weight compounds such as 4′-hydroxy-3′-methoxy acetophenone, vanillic acid, 1-(4-hydroxy-3,5-dimethoxyphenyl), benzoic acid, and octadecanoic acid were formed in the degradation of alkali lignin by LD3, indicating the cleavage of β-aryl ether, Cα-Cβ bonds, and aromatic rings in lignin. Composting results showed that inoculating LD3 improved the degradation of organic matter by 20.11% and reduced the carbon-to-nitrogen (C/N) ratio (15.66). Additionally, a higher decrease in the content of lignocellulose was observed in the LD treatment. FTIR and 3D-EEM spectra analysis indicated that inoculating LD3 promoted the decomposition of easily available organic substances and lignocellulose and the formation of aromatic structures and humic acid-like substances. In brief, the thermotolerant lignin-degrading bacterium Aneurinibacillus sp. LD3 is effective in degrading lignin and improving the quality of composting.

Fermenting and Lignin Degradability of a White-Rot Fungus Coriolopsis trogii Using Industrial Lignin as Substrate.

Bio-depolymerized the lignin macromolecules into low molecular lignin-derived aromatic compounds satisfies the requirement for carbon dioxide peaking and is also one of the important ways to realize lignin valorization. Coriolopsis trogii is a kind of less reported lignin-degrading white-rot fungus. The degradability of a self-isolated C. trogii TS01 on industrial lignins, including enzymatic hydrolysis lignin (EHL) and Kraft lignin (KL), was investigated in this paper. The results indicated that EHL could be used as an efficient carbon source to promote the cell growth and ligninolytic enzyme secretion of C. trogii TS01. Compared with using 2% glucose as carbon source, 1% EHL plus 1% glucose would increase the maximum cell dry weight, laccase activity, and manganese-dependent peroxidase activity of C. trogii TS01 by 24.8%, 164.1%, and 200%, respectively. However, the cell growth and ligninolytic enzyme secretion would be significantly inhibited in the case of 1% KL plus 1% glucose used as carbon source. As a result, at the 12th day of fermentation, the degradation rates of EHL and KL were 50.6% and 5.7%, respectively. The UV and FTIR analysis indicated that after been fermented by C. trogii TS01, S-unit content in EHL was decreased by 12.5% but G-unit content was increased by 53.7%. In conclusion, the research of this paper will provide a promising solution for the valorization of enzymatic hydrolysis lignin since the high biodegradation rate of lignin and high activity of ligninolytic enzymes could be achieved simultaneously.

Use of Anthracophyllum discolor and Stereum hirsutum as a Suitable Strategy for Delignification and Phenolic Removal of Olive Mill Solid Waste.

This study evaluated the use of the white-rot fungi (WRF) Anthracophyllum discolor and Stereum hirsutum as a biological pretreatment for olive mill solid mill waste (OMSW). The WRF strains proposed were added directly to OMSW. The assays consisted of determining the need to add supplementary nutrients, an exogenous carbon source or use agitation systems, and evaluating WRF growth, enzyme activity, phenolic compound removal and lignin degradation. The highest ligninolytic enzyme activity was found at day 10, reaching 176.7 U/L of manganese-independent peroxidase (MniP) produced by A. discolor, and the highest phenolic removal (more than 80% with both strains) was reached after 24 days of incubation. The confocal laser scanning microscopy analysis (CLSM) confirmed lignin degradation through the drop in lignin relative fluorescence units (RFU) from 3967 for untreated OMSW to 235 and 221 RFU, showing a lignin relative degradation of 94.1% and 94.4% after 24 days of treatment by A. discolor and S. hirsutum, respectively. The results demonstrate for the first time that A. discolor and S. hirsutum were able to degrade lignin and remove phenolic compounds from OMSW using this as the sole substrate without adding other nutrients or using agitation systems. This work indicates that it could be possible to design an in situ pretreatment of the valorization of OMSW, avoiding complex systems or transportation. In this sense, future research under non-sterile conditions is needed to evaluate the competition of WRF with other microorganisms present in the OMSW. The main drawbacks of this work are associated with both the low reaction time and the water addition. However, OMSW is seasonal waste produced in one season per year, being stored for a long time. In terms of water addition, the necessary optimization will be addressed in future research.

Evaluation of Lignocellulosic Wastewater Valorization with the Oleaginous Yeasts R. kratochvilovae EXF7516 and C. oleaginosum ATCC 20509

During the conversion of lignocellulose, phenolic wastewaters are generated. Therefore, researchers have investigated wastewater valorization processes in which these pollutants are converted to chemicals, i.e., lipids. However, wastewaters are lean feedstocks, so these valorization processes in research typically require the addition of large quantities of sugars and sterilization, which increase costs. This paper investigates a repeated batch fermentation strategy with Rhodotorula kratochvilovae EXF7516 and Cutaneotrichosporon oleaginosum ATCC 20509, without these requirements. The pollutant removal and its conversion to microbial oil were evaluated. Because of the presence of non-monomeric substrates, the ligninolytic enzyme activity was also investigated. The repeated batch fermentation strategy was successful, as more lipids accumulated every cycle, up to a total of 5.4 g/L (23% cell dry weight). In addition, the yeasts consumed up to 87% of monomeric substrates, i.e., sugars, aromatics, and organics acids, and up to 23% of non-monomeric substrates, i.e., partially degraded xylan, lignin, cellulose. Interestingly, lipid production was only observed during the harvest phase of each cycle, as the cells experienced stress, possibly due to oxygen limitation. This work presents the first results on the feasibility of valorizing non-sterilized lignocellulosic wastewater with R. kratochvilovae and C. oleaginosum using a cost-effective repeated batch strategy.

Optimization of White-Rot Fungi Mycelial Culture Components for Bioremediation of Pharmaceutical-Derived Pollutants

White-rot fungi can degrade a wide spectrum of environmental pollutants, including pharmaceuticals, which are not efficiently removed from wastewater by conventional methods, e.g., the activated sludge method. However, the treatment of wastewater with the use of fungal cultures (mycoremediation) also has significant limitations: among others, the need to use appropriate, often-expensive culture media. We aimed to screen 18 media ingredients, including seven agrifood byproducts for Armillaria mellea, Phanerochaete chrysosporium and Pleurotus ostreatus in submerged cultures to select the low-cost medium optimal for biomass production and laccase activity. We screened nine mathematic models to describe the relation of fungal growth and the amount of the selected byproduct in media. Finally, we tested the ability of the strain with the highest mycelial growth and enzyme-producing ability in the selected medium to degrade eight drug contaminants. Three media variants composed of byproducts provided both efficient growth and laccase production: corn steep liquor + poplar, dried distillers grains with solubles + poplar and corn steep liquor 50%. Among the investigated growth models, the Han–Levenspiel equation described well the specific growth rate in function of the nominal substrate concentration in one-component media. Pleurotus ostreatus, the fungus with the highest ligninolytic enzyme activity, cultured in medium composed of corn steep liquor, removed six of eight drug contaminants with a removal degree of 20–90% in 48 h. The obtained data on the optimal culture media consisting of insoluble components provide initial data for upscaling the process and designing an appropriate type of bioreactor for the process of removing drug contaminants from water.