Effects of Atmospheric and Room Temperature Plasma (ARTP) Mutagenesis on Physicochemical Characteristics and Immune Activity In Vitro of Hericium erinaceus Polysaccharides

Optimization of substrate formulation for Hericium erinaceus by replacing wood by straw and their effect on enzyme activities

Introduction

China is rich in straw resources. The utilization of straw in the cultivation of edible fungi partially resolves the resource conflicts between mushroom cultivation and forest industry and also contributes to environmental protection.

Methods

In this study, based on the technology of replacing wood by grass, the straw formula for mycelial culture of Hericium erinaceus was optimized with Simplex-lattice method commonly used in mixture design. By measuring the growth rate and the activity of lignocellulose degrading enzymes of mycelia in different formulations, and further combining with model optimization, the optimal formulation was screened and validated for mushroom cultivation.

Results

In the experiments, different kinds of straw used as the main material showed interaction effects, further affecting the growth rate of mycelia and the activities of laccase, cellulase, and neutral xylanase. The screened optimal formula was composed of 16.3% rice straw, 59.7% cob, 20.0% wheat bran, 2.0% gypsum, 1.0% sucrose, and 1.0% calcium superphosphate. In the mushroom cultivation, 445.69 g of fresh mushroom were obtained and the biological efficiency reached 89.14%. The growth period of the first mushroom was shortened by 7-9 days. Some nutritional components of fruiting bodies, such as crude fats (6.10%), crude proteins (152.02 g/kg), K (19.71 g/kg), P (2.48 g/kg), and Se (6.06 g/kg), were significantly higher than those of the control formula.

Discussion

These above indicators indicated that the screened formula could be applied in the high-yield and high-quality cultivation of H. erinaceus. Our study lays the foundation for expanding cultivation and strains improvement of H. erinaceus, and is conducive in promoting the rapid development of H. erinaceus industry.

Optimizing mycelial protein yield in Pleurotus djamor via ARTP mutagenesis and hybridization strategies

With the world's population rapidly increasing, the demand for high-quality protein is on the rise. Edible fungi breeding technology stands as a crucial avenue to obtain strains with high yield, high-quality protein, and robust stress resistance. To address the protein supply gap, Atmospheric and Room Temperature Plasma (ARTP) mutagenesis, and spore hybridization techniques were employed to enhance Pleurotus djamor mycelium protein production. Beginning with the original strain Pleurotus djamor JD-1, ARTP was utilized to mutate spore suspension. The optimal treatment time for Pleurotus djamor spores, determined to achieve optimal mortality, was 240 s. Through primary and secondary screenings, 6 mutant strains out of 39 were selected, exhibiting improved protein yield and growth rates compared to the original strain. Among these mutagenic strains, 240S-4 showcased the highest performance, with a mycelial growth rate of 9.5±0.71 mm/d, a biomass of 21.45±0.54 g/L, a protein content of 28.75±0.92%, and a remarkable protein promotion rate of 128.03±7.29%. Additionally, employing spore hybridization and breeding, 7 single-nuclei strains were selected for pin-two hybridization, resulting in 21 hybrid strains. The biomass and protein content of 9 hybrid strains surpassed those of the original strains. One hybrid strain, H-5, exhibited remarkable mycelial protein production, boasting a mycelial growth rate of 26.5±0.7 mm/d, a biomass of 21.70±0.46 g/L, a protein content of 28.44±0.22%, and a protein promotion rate of 128.02±1.73%. Notably, both strains demonstrated about a 28% higher mycelial protein yield than the original strains, indicating comparable effectiveness between hybrid breeding and mutagenesis breeding. Finally, we analyzed the original and selected strains by molecular biological identification, which further proved the effectiveness of the breeding method. These findings present novel insights and serve as a reference for enhancing edible fungi breeding, offering promising avenues to meet the escalating protein demand.

Effects of Cold Plasma Pretreatment on the Synthesis of Polysaccharide from Pleurotus ostreatus

Fungal polysaccharides have attracted wide attention because of their medical pharmaceutical and health care value. So far, many efforts have been made in strain improvement to produce polysaccharides on a large scale at low cost. Here, a novel cold plasma-induced strain improvement technology was employed to pretreat Pleurotus ostreatus CGMCC 5.374 by radio-frequency (RF) low-vacuum cold plasma (LVCP) for the purpose of obtaining a high-yield polysaccharide strain. The optimum pretreatment conditions including discharge power, treatment time, and working pressure were determined by single factor and orthogonal experiment in succession. Furthermore, transcriptome analysis was conducted to study the effects of RF-LVCP on cell metabolism and proliferation. Results showed that under the optimal condition of discharge power of 130 W, treatment time of 25 s and working pressure of 140 Pa, polysaccharide content in mycelium was increased by 3.16% after 6 days in comparison to the original strain. Transcriptome analysis showed that RF-LVCP is helpful for specific gene transcription profiles, Gene Ontology (GO) and KEGG pathways, of which the differentially expressed genes (DEGs) were mainly involve with the up-regulation of polysaccharide transport, physiology, synthesis and metabolism, as well as the down-regulation of polysaccharide hydrolysis and macromolecular degradation.

Recent progress of atmospheric and room-temperature plasma as a new and promising mutagenesis technology

At present, atmospheric and room-temperature plasma (ARTP) is regarded as a new and powerful mutagenesis technology with the advantages of environment-friendliness, operation under mild conditions, and fast mutagenesis speed. Compared with traditional mutagenesis strategies, ARTP is used mainly to change the structure of microbial DNA, enzymes, and proteins through a series of physical, chemical, and electromagnetic effects with the organisms, leading to nucleotide breakage, conversion or inversion, causing various DNA damages, so as to screen out the microbial mutants with better biological characteristics. As a result, in recent years, ARTP mutagenesis and the combination of ARTP with traditional mutagenesis have been widely used in microbiology, showing great potential for application. In this review, the recent progress of ARTP mutagenesis in different application fields and bottlenecks of this technology are systematically summarized, with a view to providing a theoretical basis and technical support for better application. Finally, the outlook of ARTP mutagenesis is presented, and we identify the challenges in the field of microbial mutagenesis by ARTP.

The mechanism of polysaccharide synthesis of Sanghuangporus sanghuang based on multi-omic analyses and feedback inhibition

S. sanghuang polysaccharide has various biological roles in promoting human health, however, the underlying mechanism of polysaccharide synthesis in S. sanghuang remain elusive. In the present study, the molecular structure of novel polysaccharide in the mutant S. sanghuang strain A130 with high yield of polysaccharide was characterized. The critical genes/proteins and pathways involved in polysaccharide synthesis were investigated via comparative transcriptomic, proteomic, and integrative analysis between wildtype strain SH-1 and A130. An integrated analysis of transcriptomic and proteomic results was also performed to locate potential regulators in the production of polysaccharides. The genes of cellobiohydrolase1 (CBH1) and MutS Homolog 6 (MSH6) related to glycolysis/gluconeogenesis were differentially expressed between A130 and SH-1, suggesting the potential involvement of these genes in regulating the production of polysaccharide. Proteomic analysis revealed that the abundance of Tyrosinase (TYR) and Trehalase (TREH) were substantially different between A130 and SH-1. The potential involvement of TYR in polysaccharide production was confirmed by transcriptomic-proteomic integrated analysis. The biological role of TYR and TREH in polysaccharide production was further verified by feedback inhibition of kojic acid and validamycin A, respectively. Overall, our study provides critical insights for the polysaccharide synthesis and high yield of polysaccharide through genes/pathways regulating in S. sanghuang.

Moringa oleifera leaf polysaccharides exert anti-lung cancer effects upon targeting TLR4 to reverse the tumor-associated macrophage phenotype and promote T-cell infiltration

Tumor-associated macrophages (TAMs) participate in tumorigenesis, growth, invasion as well as metastasis by facilitating an immunosuppressive tumor microenvironment. Reversing the pro-tumoral M2 phenotype of TAMs has become a hot spot in advancing cancer immunotherapy. In the current study, the content of Moringa oleifera leaf polysaccharides (MOLP) was determined and characterized, along with the anti-cancer mechanism of MOLP studied in a Lewis lung cancer (LLC) tumor-bearing mouse model and bone marrow-derived macrophages. The monosaccharide composition and gel permeation chromatography analyses show that MOLP are mainly composed of galactose, glucose, and arabinose, with approximately 17.35 kDa average molecular weight (Mw). In vivo studies demonstrate that MOLP convert TAMs from the immunosuppressive M2 phenotype to the antitumor M1 phenotype, thus inducing CXCL9 and CXCL10 expression and increasing T-cell infiltration in the tumor. Furthermore, macrophage depletion and T cell suppression demonstrated that the tumor suppressive effect of MOLP was reliant on reprogramming macrophage polarization and T cell infiltration. In vitro studies revealed that MOLP could induce the phenotypic switch from M2 macrophages to M1 by targeting TLR4. The current study highlights that MOLP are promising anticancer plant-derived polysaccharides with potential in modulating the immune microenvironment and have a bright application prospect in the immunotherapy of lung cancer.

Nonthermal Plasma Effects on Fungi: Applications, Fungal Responses, and Future Perspectives

The kingdom of Fungi is rich in species that live in various environments and exhibit different lifestyles. Many are beneficial and indispensable for the environment and industries, but some can threaten plants, animals, and humans as pathogens. Various strategies have been applied to eliminate fungal pathogens by relying on chemical and nonchemical antifungal agents and tools. Nonthermal plasma (NTP) is a potential tool to inactivate pathogenic and food-contaminating fungi and genetically improve fungal strains used in industry as enzyme and metabolite producers. The NTP mode of action is due to many highly reactive species and their interactions with biological molecules. The interaction of the NTP with living cells is believed to be synergistic yet not well understood. This review aims to summarize the current NTP designs, applications, and challenges that involve fungi, as well as provide brief descriptions of underlying mechanisms employed by fungi in interactions with the NTP components.

Application of Non-Thermal Plasma to Fungal Resources

In addition to being key pathogens in plants, animals, and humans, fungi are also valuable resources in agriculture, food, medicine, industry, and the environment. The elimination of pathogenic fungi and the functional enhancement of beneficial fungi have been the major topics investigated by researchers. Non-thermal plasma (NTP) is a potential tool to inactivate pathogenic and food-spoiling fungi and functionally enhance beneficial fungi. In this review, we summarize and discuss research performed over the last decade on the use of NTP to treat both harmful and beneficial yeast- and filamentous-type fungi. NTP can efficiently inactivate fungal spores and eliminate fungal contaminants from seeds, fresh agricultural produce, food, and human skin. Studies have also demonstrated that NTP can improve the production of valuable enzymes and metabolites in fungi. Further studies are still needed to establish NTP as a method that can be used as an alternative to the conventional methods of fungal inactivation and activation.

Characterization and Heterologous Expression of UDP-Glucose 4-Epimerase From a Hericium erinaceus Mutant with High Polysaccharide Production

Hericium erinaceus is an important medicinal fungus in traditional Chinese medicine because of its polysaccharides and other natural products. Compared terpenoids and polyketides, the analysis of synthetic pathway of polysaccharides is more difficult because of the many genes involved in central metabolism. In previous studies, A6180, encoding a putative UDP-glucose 4-epimerase (UGE) in an H. erinaceus mutant with high production of active polysaccharides, was significantly upregulated. Since there is no reliable genetic manipulation technology for H. erinaceus, we employed Escherichia coli and Saccharomyces cerevisiae to study the function and activity of A6180. The recombinant overexpression vector pET22b-A6180 was constructed for heterologous expression in E. coli. The enzymatic properties of the recombinant protein were investigated. It showed that the recombinant A6180 could strongly convert UDP-α-D-glucose into UDP-α-D-galactose under optimal conditions (pH 6.0, 30°C). In addition, when A6180 was introduced into S. cerevisiae BY4742, xylose was detected in the polysaccharide composition of the yeast transformant. This suggested that the protein coded by A6180 might be a multifunctional enzyme. The generated polysaccharides with a new composition of sugars showed enhanced macrophage activity in vitro. These results indicate that A6180 plays an important role in the structure and activity of polysaccharides. It is a promising strategy for producing polysaccharides with higher activity by introducing A6180 into polysaccharide-producing mushrooms.

Enhanced Erinacine A Production by Hericium erinaceus Using Solid-State Cultivation

Hericium erinaceus (HE) is a large edible medicinal fungus. Erinacine A (ErA) is a secondary metabolite presented in the mycelia of HE, with pharmacological effects as a nerve growth factor on the central nervous system. In this study, solid-state cultivation of HE was carried out in Petri dishes and glass jars for the production of mycelial biomass and ErA. The potato dextrose agar (PDA) had the highest mycelial biomass at an optimal temperature of 25 °C, but no ErA was found in the agar media. In glass jar cultivation, the mycelial biomass and specific yield of ErA in different substrates, particle sizes, substrate weights, nitrogen sources, and inorganic salts were investigated. The ErA was purified by a self-pack silica gel column and a semi-preparative HPLC and was identified by liquid chromatography-tandem mass spectrometer. The best conditions for solid-state cultivation of HE when using corn kernel as substrate, particle size less than 2.38 mm, and addition of 10mM ZnSO4, 7H2O, mycelial biomass of 50.24 mg cell dry weight/g substrate was obtained, in addition, the specific yield of ErA could reach 165.36 mg/g cell dry weight.

Design and construction of novel biocatalyst for bioprocessing: Recent advances and future outlook

Bioprocess, a biocatalysis-based technology, is becoming popular in many research fields and widely applied in industrial manufacturing. However, low bioconversion, low productivity, and high costs during industrial processes are usually the limitation in bioprocess. Therefore, many biocatalyst strategies have been developed to meet these challenges in recent years. In this review, we firstly discuss protein engineering strategies, which are emerged for improving the biocatalysis activity of biocatalysts. Then, we summarize metabolic engineering strategies that are promoting the development of microbial cell factories. Next, we illustrate the necessity of using the combining strategy of protein engineering and metabolic engineering for efficient biocatalysts. Lastly, future perspectives about the development and application of novel biocatalyst strategies are discussed. This review provides theoretical guidance for the development of efficient, sustainable, and economical bioprocesses mediated by novel biocatalysts.

Key metabolism pathways and regulatory mechanisms of high polysaccharide yielding in Hericium erinaceus

Background

Hericium erinaceus, a rare edible and medicine fungus, is widely used in the food and medical field. Polysaccharides from H. erinaceus are the main bioactive compound that exert high bioactive value in the medical and healthcare industries.

Results

The genome of H. erinaceus original strain HEA was reported 38.16 Mb, encoding 9780 predicted genes by single-molecule, real-time sequencing technology. The phylogenomic analysis showed that H. erinaceus had the closest evolutionary affinity with Dentipellis sp. The polysaccharide content in the fermented mycelia of mutated strains HEB and HEC, which obtained by ARTP mutagenesis in our previous study, was improved by 23.25 and 47.45%, and a new β-glucan fraction with molecular weight 1.056 × 10⁶ Da was produced in HEC. Integrative analysis of transcriptome and proteomics showed the upregulation of the carbohydrate metabolism pathway modules in HEB and HEC might lead to the increased production of glucose-6P and promote the repeating units synthesis of polysaccharides. qPCR and PRM analysis confirmed that most of the co-enriched and differentially co-expressed genes involved in carbohydrate metabolism shared a similar expression trend with the transcriptome and proteome data in HEB and HEC. Heatmap analysis showed a noticeably decreased protein expression profile of the RAS-cAMP-PKA pathway in HEC with a highly increased 47.45% of polysaccharide content. The S phase progression blocking experiment further verified that the RAS-cAMP-PKA pathway’s dysfunction might promote high polysaccharide and β-glucan production in the mutant strain HEC.

Conclusions

The study revealed the primary mechanism of the increased polysaccharide synthesis induced by ARTP mutagenesis and explored the essential genes and pathways of polysaccharide synthesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07480-x.

The Structural Characteristics and Biological Activities of Intracellular Polysaccharide Derived from Mutagenic Sanghuangporous sanghuang Strain

Sanghuangporous sanghuang is a rare medicinal fungus which contains polysaccharide as the main active substance and was used to treat gynecological diseases in ancient China. The intracellular polysaccharide yield of S. sanghuang was enhanced by the strain A130 which was screened from mutant strains via atmospheric and room temperature plasma (ARTP) mutagenesis. The objective of this research was to investigate the effects of ARTP mutagenesis on structural characteristics and biological activities of intracellular polysaccharides from S. sanghuang. Six intracellular polysaccharide components were obtained from S. sanghuang mycelia cultivated by the mutagenic strain (A130) and original strain (SH1), respectively. The results revealed that the yields of polysaccharide fractions A130-20, A130-50 and A130-70 isolated from the mutagenic strain fermentation mycelia were significantly higher than those of the original ones by 1.5-, 1.3- and 1.2-fold, and the clear physicochemical differences were found in polysaccharide fractions precipitated by 20% ethanol. A130-20 showed a relatively expanded branching chain with higher molecular weight and better in vitro macrophage activation activities and the IL-6, IL-1, and TNF-α production activities of macrophages were improved by stimulation of A130-20 from the mutagenic strain. This study demonstrates that ARTP is a novel and powerful tool to breed a high polysaccharide yield strain of S. sanghuang and may, therefore, contribute to the large-scale utilization of rare medicinal fungi.

Elevated H2AX Phosphorylation Observed with kINPen Plasma Treatment Is Not Caused by ROS-Mediated DNA Damage but Is the Consequence of Apoptosis

Phosphorylated histone 2AX (γH2AX) is a long-standing marker for DNA double-strand breaks (DSBs) from ionizing radiation in the field of radiobiology. This led to the perception of γH2AX being a general marker of direct DNA damage with the treatment of other agents such as low-dose exogenous ROS that unlikely act on cellular DNA directly. Cold physical plasma confers biomedical effects majorly via release of reactive oxygen and nitrogen species (ROS). In vitro, increase of γH2AX has often been observed with plasma treatment, leading to the conclusion that DNA damage is a direct consequence of plasma exposure. However, increase in γH2AX also occurs during apoptosis, which is often observed with plasma treatment as well. Moreover, it must be questioned if plasma-derived ROS can reach into the nucleus and still be reactive enough to damage DNA directly. We investigated γH2AX induction in a lymphocyte cell line upon ROS exposure (plasma, hydrogen peroxide, or hypochlorous acid) or UV-B light. Cytotoxicity and γH2AX induction was abrogated by the use of antioxidants with all types of ROS treatment but not UV radiation. H2AX phosphorylation levels were overall independent of analyzing either all nucleated cells or segmenting γH2AX phosphorylation for each cell cycle phase. SB202190 (p38-MAPK inhibitor) and Z-VAD-FMK (pan-caspase inhibitor) significantly inhibited γH2AX induction upon ROS but not UV treatment. Finally, and despite γH2AX induction, UV but not plasma treatment led to significantly increased micronucleus formation, which is a functional read-out of genotoxic DNA DSBs. We conclude that plasma-mediated and low-ROS γH2AX induction depends on caspase activation and hence is not the cause but consequence of apoptosis induction. Moreover, we could not identify lasting mutagenic effects with plasma treatment despite phosphorylation of H2AX.

The Effect of Hemicellulose and Lignin on Properties of Polysaccharides in Lentinus edodes and Their Antioxidant Evaluation

Lentinus edodes, whose polysaccharides possess diverse bioactivities, commonly grows on hardwood sawdust composed of hemicellulose, lignin and cellulose. In this study the effect of hemicellulose and lignin on the growth of mycelia, as well as the physicochemical properties of polysaccharides from L. edodes mycelia (LEPs) were investigated. The antioxidant properties of LEPs were evaluated through radical scavenging assays in vitro and through the Caenorhabditis elegans model in vivo. The results showed that hemicellulose at a concentration of 4% increased the yield of the mycelia biomass to twice that of the control group. Meanwhile, when cultured with 4.0% hemicellulose, the polysaccharide content of the mycelia was raised by 112.2%. In addition, the appropriate concentration of lignin could stimulate mycelia growth and polysaccharide biosynthesis in L. edodes. Monosaccharide composition analysis showed that a higher content of xylose was found when mycelia were cultured with higher concentrations of hemicellulose. The molecular structure, including the molecular weight distribution and configuration type, was affected by hemicellulose and lignin. Antioxidant assays indicated that LEPs supplemented with hemicellulose and/or lignin possessed higher radical scavenging abilities in vitro and exhibited a thermal resistance effect on C. elegans, implying that the antioxidant effect is potent in vivo. In summary, the addition of hemicellulose and lignin improved the biosynthesis and bioactivity of LEPs.