Green potential of Pleurotus spp. in biotechnology

A systematic study on the characteristics and applications of laccases produced by fungi: insights on their potential for biotechnologies

Laccases are polyphenol oxidase enzymes and form the enzyme complex known for their role in wood decomposition and lignin degradation. The present study aimed to systematically review the state-of-the-art trends in scientific publications on laccase enzymes of the last 10 years. The main aspects checked included the laccase-producing fungal genera, the conditions of fungal growth and laccase production, the methods of immobilization, and potential applications of laccase. After applying the systematic search method 177 articles were selected to compound the final database. Although various fungi produce laccase, most studies were Trametes and Pleurotus genera. The submerged fermentation (SmF) has been the most used, however, the use of solid-state fermentation (SSF) appeared as a promising technique to produce laccase when using agro-industrial residues as substrates. Studies on laccase immobilization showed the covalent bonding and entrapment methods were the most used, showing greater efficiency of immobilization and a high number of enzyme reuses. The main use of the laccase was in bioremediation, especially in the discoloration of dyes from the textile industry and the degradation of pharmaceutical waste. Implications and consequences of all these findings in biotechnology and environment, as well as the trends and gaps of laccase research were discussed.

PriA is involved in Pleurotus ostreatus development and defense against Pseudomonas tolaasii

Pleurotus ostreatus is a crucial commercial mushroom widely cultivated for diverse uses. Scientists have worked on breeding disease-resistant and high-yielding varieties to secure food supply. Studies on the molecular genetic mechanism of growth and development can provide valuable information to facilitate crop breeding programs by genetic engineering. Aegerolysins are pore-forming proteins widely distributed in both prokaryotes and eukaryotes, which are reported to have haemolytic activity and be involved in the early stages of fructification. The present study aimed to explore biological function of a differential expressed aegerolysin gene PriA in P. ostreatus. The expression level of PriA gene was higher in primordium and fruiting body than that in mycelium. The PriA expression in overexpression (OE) and RNAi interference (RNAi) strains was detected by qRT-PCR. The RNAi strains grew at slightly slower rates and advanced producing yellow pigments than the wild type, while OE strains showed no prominent phenotypic characteristics. Furthermore, Pseudomonas tolaasii infection assays showed that the PriA OE strains could enhance mycelia and caps resistance to P. tolaasii. These data demonstrate PriA from P. ostreatus play an essential role in mycelial development and increase antagonism against P. tolaasii. Our study provides some reference information on interactions between edible fungi and pathogenic bacteria and offers a new resistance-conferring gene for breeding.

Silencing of the Laccase (lacc2) Gene from Pleurotus ostreatus Causes Important Effects on the Formation of Toxocyst-like Structures and Fruiting Body

A wide variety of biological functions, including those involved in the morphogenesis process of basidiomycete fungi, have been attributed to laccase enzymes. In this work, RNA interference (RNAi) was used to evaluate the role of the laccase (lacc2) gene of Pleurotus ostreatus PoB. Previously, transformant strains of P. ostreatus were obtained and according to their level of silencing they were classified as light (T7), medium (T21) or severe (T26 and T27). The attenuation of the lacc2 gene in these transformants was determined by RT-PCR. Silencing of lacc2 resulted in a decrease in laccase activity between 30 and 55%, which depended on the level of laccase expression achieved. The silenced strains (T21, T26, and T27) displayed a delay in the development of mycelium on potato dextrose agar (PDA) medium, whereas in the cultures grown on wheat straw, we found that these strains were incapable of producing aerial mycelium, primordia, and fruiting bodies. Scanning electron microscopy (SEM) showed the presence of toxocyst-like structures. The highest abundance of these structures was observed in the wild-type (PoB) and T7 strains. However, the abundance of toxocysts decreased in the T21 and T26 strains, and in T27 they were not detected. These results suggest that the presence and abundance of toxocyst-like structures are directly related to the development of fruiting bodies. Furthermore, our data confirm that lacc2 is involved in the morphogenesis process of P. ostreatus.

From pomiculture waste to biotechnological raw material: efficient transformation using ligninosomes and cellulosomes from Pleurotus spp

The goal of this study was to determine the capacity of Pleurotus spp. lignocellulosome to transform frequent pomiculture residues (grapevine-, plum-, and raspberry sawdust) into raw materials for biotechnological processes. All three lignocellulosics induced the synthesis of ligninolytic and cellulolytic enzymes in the tested species. Laccase was dominant in the ligninolytic cocktail, with a maximum activity of 40,494.88 U L-1 observed after the cultivation of P. pulmonarius on grapevine sawdust. Grapevine sawdust also proved to be the optimal substrate for the synthesis of versatile peroxidases especially in P. eryngii (1010.10 U L-1), while raspberry sawdust favored the production of Mn-dependent peroxidase in P. pulmonarius (479.17 U L-1). P. pulmonarius was the dominant cellulolytic agent and raspberry sawdust was optimal for the synthesis of xylanases, and endo- and exo-cellulases (15,746.35 U L-1, 9741.56 U L-1, and 836.62 U L-1), while grapevine sawdust mostly induced β-glucosidase activity (166.11 U L-1). The degree of residues delignification was more substrate- than species-dependent, ranging between 6.44 and 23.72% after the fermentation of grapevine and raspberry sawdust with P. pulmonarius. On the other hand, the lowest level of cellulose consumption was also observed on raspberry sawdust after the cultivation of P. eryngii, which together with high delignification also induced the highest selectivity index (1.27). The obtained results show the exceptional lignocellulolytic potential of Pleurotus spp. enzyme cocktails which opens up many possibilities for their application in numerous biotechnological processes.

Green Biotechnology of Oyster Mushroom (Pleurotus ostreatus L.): A Sustainable Strategy for Myco-Remediation and Bio-Fermentation

The field of biotechnology presents us with a great chance to use many organisms, such as mushrooms, to find suitable solutions for issues that include the accumulation of agro-wastes in the environment. The green biotechnology of mushrooms (Pleurotus ostreatus L.) includes the myco-remediation of polluted soil and water as well as bio-fermentation. The circular economy approach could be effectively achieved by using oyster mushrooms (Pleurotus ostreatus L.), of which the substrate of their cultivation is considered as a vital source for producing biofertilizers, animal feeds, bioenergy, and bio-remediators. Spent mushroom substrate is also considered a crucial source for many applications, including the production of enzymes (e.g., manganese peroxidase, laccase, and lignin peroxidase) and bioethanol. The sustainable management of agro-industrial wastes (e.g., plant-based foods, animal-based foods, and non-food industries) could reduce, reuse and recycle using oyster mushrooms. This review aims to focus on the biotechnological applications of the oyster mushroom (P. ostreatus L.) concerning the field of the myco-remediation of pollutants and the bio-fermentation of agro-industrial wastes as a sustainable approach to environmental protection. This study can open new windows onto the green synthesis of metal-nanoparticles, such as nano-silver, nano-TiO2 and nano-ZnO. More investigations are needed concerning the new biotechnological approaches.

Edible Mushrooms as Novel Myco-Therapeutics: Effects on Lipid Level, Obesity and BMI

Obesity, usually indicated by a body mass index of more than 30 kg/m², is a worsening global health issue. It leads to chronic diseases, including type II diabetes, hypertension, and cardiovascular diseases. Conventional treatments for obesity include physical activity and maintaining a negative energy balance. However, physical activity alone cannot determine body weight as several other factors play a role in the overall energy balance. Alternatively, weight loss may be achieved by medication and surgery. However, these options can be expensive or have side effects. Therefore, dietary factors, including dietary modifications, nutraceutical preparations, and functional foods have been investigated recently. For example, edible mushrooms have beneficial effects on human health. Polysaccharides (essentially β-D-glucans), chitinous substances, heteroglycans, proteoglycans, peptidoglycans, alkaloids, lactones, lectins, alkaloids, flavonoids, steroids, terpenoids, terpenes, phenols, nucleotides, glycoproteins, proteins, amino acids, antimicrobials, and minerals are the major bioactive compounds in these mushrooms. These bioactive compounds have chemo-preventive, anti-obesity, anti-diabetic, cardioprotective, and neuroprotective properties. Consumption of edible mushrooms reduces plasma triglyceride, total cholesterol, low-density lipoprotein, and plasma glucose levels. Polysaccharides from edible mushrooms suppress mRNA expression in 3T3-L1 adipocytes, contributing to their anti-obesity properties. Therefore, edible mushrooms or their active ingredients may help prevent obesity and other chronic ailments.

Use of green light to improve the production of lignocellulose-decay enzymes by Pleurotus spp. in liquid cultivation

The influence of green light on mycelium biomass growth and extracellular enzyme activities of edible mushrooms from the Pleurotus genus, which is popularly cultivated all over the world, were investigated. The mycelium of seven strains of five species of Pleurotus (P. citrinopileatus, P. djamor, P. eryngii, P. ostreatus, and P. pulmonarius) was grown in liquid medium at 28 °C in the dark or under green light (515-530 nm). The light source was light-emitting diodes (LED) with photon flux density adjusted to 20 μmol m^-2 s^-1 that was kept on throughout the cultivation period. After 12 days of growth, the mycelium was recovered and used for biomass determination and the cultivation medium was used to total cellulase, endoglucanase, xylanase, and laccase activities determination. Green light reduced the mycelial biomass growth of Pleurotus spp. but increased the cellulolytic and xylanolytic activities. The cellulolytic activity of most strains increased in the presence of green light with increases ranging from 1.5 times (P. ostreatus endoglucanase) to 8 times (P. citrinopileatus total cellulase and endoglucanase). Green light reduced laccase activity for most strains with the greatest reduction for P. eryngii (2.2 times lower). The specific enzymatic activity of cellulase and endoglucanase from P. citrinopileatus, increased by 31 times and 30 times, respectively, compared to the dark. Also, the specific laccase and xylanase activities of P. pulmonarius increased 4.4 times and 6.8 times, respectively, under green light. The use of light at particular wavelengths can be a viable strategy to increase the production of enzymes for different biotechnological applications and species of Pleurotus are particularly interesting for this purpose.

Comparative study of single cultures and a consortium of white rot fungi for polychlorinated biphenyls treatment

AIMS

To evaluate the mycoremediation of polychlorinated biphenyls (PCBs) by either single cultures or binary consortia of Pleurotus pulmonarius LBM 105 and Trametes sanguinea LBM 023.

METHODS AND RESULTS

PCBs tolerance, removal capacity, toxicity reduction and ligninolytic enzyme expression were assessed when growing single culture and binary consortium of fungus in 217 mg l^-1 of a technical mixture of Aroclor 1242, 1254 and 1260 in transformer oil. A decrease in tolerance and variation in ligninolytic enzyme secretion were observed in PCB-amended solid media. Pleurotus pulmonarius LBM 105 mono-culture was able to remove up to 95·4% of PCBs, whereas binary consortium and T. sanguinea LBM 023 could biodegrade about 55% after 24 days. Significant detoxification levels were detected in all treatments by biosorption mechanism.

CONCLUSIONS

Pleurotus pulmonarius LBM 105 in single culture had the best performance regarding PCBs biodegradation and toxicity reduction. Ligninolytic enzyme secretion changed in co-culture.

SIGNIFICANCE AND IMPACT OF THE STUDY

The evaluation of PCBs bioremediation effectiveness of basidiomycetes consortium in terms of PCB removal, toxicity and ligninolytic enzyme production to unravel the differences between using individual cultures or consortium has not been reported. The results from this study enable the selection of P. pulmonarius LBM 105 mono-culture to bioremediate PCBs as it showed higher efficiency compared to binary consortium with T. sanguinea LBM 023 for potential decontamination of PCB-contaminated transformer oil.

Therapeutic applications of mushrooms and their biomolecules along with a glimpse of in silico approach in neurodegenerative diseases

Neurodegenerative diseases (NDs) represent a common neurological pathology that determines a progressive deterioration of the brain or the nervous system. For treating NDs, comprehensive and alternative medicines have attracted scientific researchers' attention recently. Edible mushrooms are essential for preventing several age-based neuronal dysfunctions such as Parkinson's and Alzheimer's diseases. Mushroom such as Grifola frondosa, Lignosus rhinocerotis, Hericium erinaceus, may improve cognitive functions. It has also been reported that edible mushrooms (basidiocarps/mycelia extracts or isolated bioactive compounds) may reduce beta-amyloid-induced neurotoxicity. Medicinal mushrooms are being used for novel and natural compounds that help modulate immune responses and possess anti-cancer, anti-microbial, and anti-oxidant properties. Compounds such as polyphenols, terpenoids, alkaloids, sesquiterpenes, polysaccharides, and metal chelating agents are validated in different ND treatments. This review aims to assess mushrooms' role and their biomolecules utilization for treating different kinds of NDs. The action mechanisms, presented here, including reducing oxidative stress, neuroinflammation, and modulation of acetylcholinesterase activity, protecting neurons or stimulation, and regulating neurotrophins synthesis. We also provide background about neurodegenerative diseases and in-silico techniques of the drug research. High costs associated with experiments and current ethical law imply efficient alternatives with limited cost value. In silico approaches provide an alternative method with low cost that has been successfully implemented to cure ND disorders in recent days. We also describe the applications of computational procedures such as molecular docking, virtual high-throughput screening, molecular dynamic (MD) simulation, quantum-mechanical methods for drug design. They were reported against various targets in NDs.

Bioactivity assessment of exopolysaccharides produced by Pleurotus pulmonarius in submerged culture with different agro-waste residues

Pleurotus spp. are white-rot fungi that utilize different agro-wastes to produce useful biologically active compounds. In this study, exopolysaccharides (EPS) were produced by Pleurotus pulmonarius in submerged culture supplemented with different agro-wastes. Functional groups in EPS were revealed using Fourier Transform-Infrared (FT-IR) spectroscopy. Antimicrobial activity of EPS was tested against microorganisms using agar well diffusion. Scavenging potentials of EPS was tested against 1, 1- diphenyl-2-picryhydrazyl (DPPH), hydroxyl (OH), iron (Fe2+) and nitric oxide (NO) radicals. In vitro prebiotic activity of EPS was carried out. The highest yield (5.60 g/L) of EPS was produced by P. pulmonarius in submerged culture supplemented with groundnut shell (20.0 g/L). The functional groups in EPS were hydroxyl (-OH), methyl (-CH3), ketone (-RCOH) and carbonyl group (-C=O). EPS displayed zones of inhibition (5.00-14.00 mm) against tested microorganisms. Scavenging activity of EPS ranged from 65.70-81.80% against DPPH. EPS supported the growth of Lactobacillus delbrueckii and Streptococcus thermophiles with values ranged from 3.04 × 104-3.40 × 104 cfu/ml and 2.50 × 104-2.81 × 104 cfu/ml, respectively. Submerged culture of P. pulmonarius with addition of agro-wastes enhanced yield of EPS. The EPS exhibited bio-functional properties like antimicrobial, antioxidant and prebiotic activities. Hence, agrowastes can be recycled in submerged fermentation with fungi to produce promising biomaterials for biopharmaceutical applications.

A comparative study of antimicrobial and anti-inflammatory efficiency of modified solvent evaporated and vacuum oven dried bioactive components of Pleurotus floridanus

In the present study, we compared vacuum microwave oven drying Vacuum Oven Drying (VOD) and modified solvent evaporation (MSE) assisted methanolic mushroom extracts for their antimicrobial and anti-inflammatory efficacy. MSE extract showed significantly (p < 0.05) higher total phenolic content (64.4 mg/g) followed by flavonoid content (20.62 mg/g), ascorbic acid (17.54 mg/g), β-carotene content (12.52 mg/g), and lycopene (9.57 mg/g) content than that of VOD extract. MSE showed a significantly (p < 0.05) higher zone of inhibition against all selected microorganisms as compared to VOD extract. During the time-kill study, the MSE extract inhibited significantly (p < 0.05) higher growth of Staphylococcus aureus followed by Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli than that of VOD extract. Also, MSE extract showed significantly (p < 0.05) higher anti-inflammatory activity in comparison with VOD extract during the Human Red Blood Cell (HRBC) membrane stabilization test and albumin denaturation test. MSE extract revealed significantly (p < 0.05) higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) and N₂O₂ scavenging assay than that of VOD extract, however, statistically, MSE extract showed comparable results with Butylated Hydroxyanisole (BHA) and Butylated Hydroxytoluene (BHT). During the characterization of the selected extract, Fourier transform infrared spectroscopy confirmed the functional groups of the flavonoid content, ascorbic acid, β-carotene, and lycopene. Quantitative analysis of gallic acid (54.32 mg/g) and rutin content (14.80 mg/g) was revealed using a high-pressure liquid chromatogram.

Cultivation and Nutritional Value of Prominent Pleurotus spp.: An Overview

Pleurotus species are commercially essential mushrooms and widely cultivated throughout the world. The production of Pleurotus mushrooms alone accounts for around 25% of that total cultivated mushrooms globally. In America and Europe, Pleurotus species are considered specialty mushrooms, whereas, in Korea, their cultivation is economically profitable, and it is one of the highly consumed species. Pleurotus species are predominantly found in tropical forests and often grow on fallen branches, dead and decaying tree stumps, and wet logs. Biographical studies have shown that the Pleurotus genus is among the more conspicuous fungi that induce wood decay in terrestrial ecosystems worldwide due to its formidable lignin-modifying enzymes, including laccase and versatile peroxidases. Pleurotus species can be grown easily due to their fast colonization nature on diversified agro-substrates and their biological efficiency 100%. Pleurotus mushrooms are rich in proteins, dietary fiber, essential amino acids, carbohydrates, water-soluble vitamins, and minerals. These mushrooms are abundant in functional bioactive molecules, though to influence health. Pleurotus mushrooms are finding unique applications as flavoring, aroma, and excellent preservation quality. Apart from its unique applications, Pleurotus mushrooms have a unique status delicacy with high nutritional and medicinal values. The present review provides an insight into the cultivation of Pleurotus spp. using different agro-waste as growth substances paying attention to their effects on the growth and chemical composition.

Characterization of the Nutritional Composition of a Biotechnologically Produced Oyster Mushroom and its Physiological Effects in Obese Zucker Rats

SCOPE

Sustainable protein sources are needed to meet the increasing protein demands of a continuously growing world population. This study is focused on the biotechnological production of a protein rich oyster mushroom (Pleurotus sajor-caju; PSC) by valorization of an agricultural side stream and the evaluation of the physiological effects of PSC in a rat model of metabolic syndrome.

METHODS AND RESULTS

PSC is produced via submerged cultivation in a 150 L bioreactor that utilizes isomaltulose molasses as its sole carbon source, and is further analyzed for its nutritional composition. A feeding trial is performed using Zucker rats which are fed a 5% PSC supplemented diet, for 4 weeks. Biochemical analyses reveal a significant reduction of the liver lipid concentrations and liver inflammation in the PSC fed obese rats in comparison to the obese rats from the control group. Hepatic qPCR analyses, differential transcript profiling, and enzyme activity measurements reveal a number of altered pathways that may be responsible for these anti-steatotic and anti-inflammatory effects of the mushroom.

CONCLUSION

Bioconversion of a low quality agricultural side stream to an improved protein source is performed by submerged cultured PSC, and the obtained mycelium shows strong anti-steatotic and anti-inflammatory effects.

Aegerolysins from the fungal genus Pleurotus - Bioinsecticidal proteins with multiple potential applications

The aegerolysin proteins ostreolysin A6, pleurotolysin A2 and erylysin A are produced by mushrooms of the genus Pleurotus. These aegerolysins can interact specifically with sphingolipid-enriched membranes. In particular, they strongly bind insect cells and to artificial lipid membranes that contain physiologically relevant concentrations of the main invertebrate-specific sphingolipid, ceramide phosphoethanolamine. Moreover, the aegerolysins permeabilise these membranes when combined with their protein partner pleurotolysin B, which contains a membrane-attack-complex/perforin domain. These aegerolysin/ pleurotolysin B complexes show strong and selective toxicity towards western corn rootworm larvae and adults and Colorado potato beetle larvae. Their insecticidal activities arise through aegerolysin binding to ceramide phosphoethanolamine in the insect midgut. This mode of membrane binding is different from those described for similar aegerolysin-based complexes of bacterial origin (e.g., Cry34Ab1/Cry35Ab1), or other Bacillus thuringiensis proteinaceous crystal toxins, which associate with protein receptors. The ability of Pleurotus aegerolysins to specifically interact with sphingolipid-enriched domains in mammalian cells can be further exploited to visualize lipid rafts in living cells, and to treat certain types of tumours and metabolic disorders. Finally, these proteins can strongly enhance fruiting initiation of P. ostreatus even when applied externally. In this review, we summarise the current knowledge of the potential biotechnological and biomedical applications of the Pleurotus aegerolysins, either alone or when complexed with pleurotolysin B, with special emphasis on their bioinsecticidal effects.

Modulation of agronomic and nutritional response of Pleurotus eryngii strains by utilizing glycine betaine enriched cotton waste

BACKGROUND

This study aimed to evaluate the possibility of cotton waste enrichment with glycine betaine (GB) for production of two strains (P9, P10) of king oyster (Pleurotus eryngii). Cotton waste was used as (100%) control (T0 = cotton waste) and augmented with various combinations of GB, (T1 = 2 mmol L^-1 , T2 = 4 mmol L^-1 , T3 = 6 mmol L^-1 , T4 = 8 mmol L^-1 and T5 = 10 mmol L^-1 ). The response of king oyster to GB was evaluated by earliness, yield, biological efficiency (BE), minerals (nitrogen, phosphorus, potassium, zinc (Zn), copper (Cu), magnesium (Mg), manganese (Mn), iron (Fe), sodium (Na), calcium (Ca)), total sugars, total soluble solids, reducing sugars, non-reducing sugars, ascorbic acid, proximate (crude protein, carbohydrates, crude fibers, ash, fats) content of fruiting body and Fourier-transform infrared (FTIR) spectroscopy analysis compared with the control substrate (cotton waste).

RESULTS

The earliness, yield, and BE were higher as compared to control substrate and increased with an augmentation in the concentration of GB within the cotton waste. Two strains showed (on dry weight basis) 33.9-54.9 mg g^-1 nitrogen, 6.8-12.5 mg g^-1 phosphorus, 16.9-25.1 mg g^-1 potassium, 40.5-64.2 mg kg^-1 Zn, 17.1-37.3 mg kg^-1 Cu, 1174-1325 mg kg^-1 Mg, 20.1-29.1 mg kg^-1 Mn, 129-265 mg kg^-1 Fe, 779-835 mg kg^-1 Ca), 6.3%-11.3% total sugars, 7.3-14.9 °Brix total soluble solids, 2.1-7.3% reducing sugars, 10.4-18.1% crude protein, 3.6-4.4% crude fiber and 5.6-16.7 mg (100 g)^-1 on various concentration of GB enrich cotton waste. Cotton waste enriched with GB significantly affected nutritional profile of king oyster mushroom.

CONCLUSION

The results revealed that GB enriched cotton waste can be used as an innovative substrate to enhance the yield and quality of king oyster mushroom. © 2019 Society of Chemical Industry.