Production of extracellular polysaccharides by submerged mycelial culture of Laetiporus sulphureus var. miniatus and their insulinotropic properties

Pilot-Scale Production of the Natural Colorant Laetiporic Acid, Its Stability and Potential Applications

Laetiporus sulphureus, a wood-decaying basidiomycete, produces yellow-orange pigments in fruiting bodies and, as was recently shown, in submerged cultivated mycelia. Out of four strains, the most potent laetiporic acid producer was identified and its yield compared in different media. The complex Moser b medium was replaced by potato dextrose broth, achieving higher yields at a lower cost. Cultivation was then scaled up from shake flask to a 7 L stirred tank bioreactor. Optimization of parameters led to increased product concentrations up to 1 g L−1, the highest yield reported so far. An in situ product recovery strategy with a biphasic system was established, increasing the yield by 19% on the shake flask scale. A crude ethanolic extract of the biomass was examined for color stability and application trials. In contrast to what has been suggested in the past, the pigment showed limited long-term stability to oxygen and light, but was stable under storage in the dark at 4 °C under nitrogen. The orange extract was successfully incorporated into different matrices like foods, cosmetics and textiles. Laetiporic acid can potentially replace petrochemical based synthetic dyes, and can thus support the development of a circular bioeconomy.

Chromosome-Level Genome Sequences, Comparative Genomic Analyses, and Secondary-Metabolite Biosynthesis Evaluation of the Medicinal Edible Mushroom Laetiporus sulphureus

Laetiporus sulphureus mushroom is a complementary and alternative medicine that has anticancer, antioxidation, and analgesic effects and immunomodulatory activity; it is used as a treatment for cough and rheumatism and is a functional food that can improve physical fitness. Even though L. sulphureus has garnered considerable biotechnological and pharmacological interest due to its excellent cellulose-degrading ability and diverse biological activities, its biosynthetic potential regarding polysaccharides and secondary metabolites has not been thoroughly examined. In this study, we sequenced and assembled the whole genome of a wild L. sulphureus isolate, NWAFU-1, from the Qinling Mountains in China. Comparative genomes analysis revealed genomic differences between subspecies, and phylogenomic analysis revealed evolutionary divergence as well as genome expansion and contraction of individual Polyporaceae family species. Bioinformatics investigation identified candidate genes associated with mating type, polysaccharide synthesis, carbohydrate-active enzymes, and secondary-metabolite biosynthesis, which included multiple terpenoids, nonribosomal peptides, and polyketides. The locations of biosynthetic core genes were mapped and displayed on chromosomes and contigs. Totals of 143 proteins from 126 coding genes were identified and divided into 14 cytochrome P450 families. Furthermore, the biosynthetic network of tetracyclic triterpenoid active components was postulated by genome mining of related genes combined with the molecular network of metabolites. The genome analysis of L. sulphureus in this study improves the understanding of the biosynthesis of active compounds, which will lay a theoretical foundation for subsequent research on active-compound biosynthesis and promote the application of Laetiporus in the field of drug research and functional-food creation. IMPORTANCE L. sulphureus is a parasitic basidiomycete fungus that causes brown rot. The fruiting bodies of L. sulphureus are used as ancient medicines in China and Europe to cure cancer, analgesia, cough, and rheumatism and are considered a functional food that regulates the body and improves health. L. sulphureus was inferred to be a tetrapolar system based on a high-quality genome, which will aid molecular breeding and artificial farming. Screening polysaccharide synthesis candidate genes and comparing carbohydrate-associated genes in brown-rot basidiomycetes help understand their growth. Identifying core genes for secondary-metabolite biosynthesis, gene cluster family analysis, and comparative cluster analysis will guide heterologous-biosynthesis investigations of these genes and help elucidate the biosynthetic pathways for L. sulphureus bioactive natural components. The biosynthesis network of tetracyclic triterpenes was mapped using metabolite profiling and genome scanning. This work explores the biosynthetic capacity of L. sulphureus-derived natural products and lays the foundation for biosynthetic studies of them.

Bioactive components of Laetiporus species and their pharmacological effects

Laetiporus species are brown rot fungi belonging to the order Polyporales in the division Basidiomycota. These species produce a variety of metabolites and provide a great source of natural material for the screening of medicinally active natural products or their derivatives. This review summarizes the research progress on bioactive metabolites of Laetiporus species up to April 2022, including biological macromolecules, for instance, polysaccharides and lectins, as well as 80 reported small molecule chemical components (15 sterols, 29 triterpenes, 10 sesquiterpenes, 5 polyenes, 10 volatile compounds, and 11 other compounds). These metabolites exhibit antimicrobial, anticancer, antioxidant, hepatoprotective, anti-inflammatory, and antidiabetic activities. Genome mining predicted 23 terpene synthases, 7 polyketide synthases, and 9 non-ribosomal peptide synthases involved in bioactive metabolites biosynthesis, which were analyzed by antiSMASH in L. sulphureus genome. This review will provide a basis for the biosynthesis of active components in Laetiporus species and a reference for the research of medical precursors. KEY POINTS: • The mini-review summarized 80 secondary metabolites of Laetiporus spp. • The main pharmacological activities of Laetiporus spp. were summarized. • Biosynthetic genes of terpenoids, polyketides, and non-ribosomal peptides were also summarized.

Improved Production and Insulinotropic Properties of Exopolysaccharide by Phellinus igniarius in Submerged Cultures

Phellinu igniarius (P. igniarius), a basidiomycete belonging to the family Polyporaceae, is a medicinal basidiomycetous fungus belonging to the Hymenochaetaceae and is an excellent remedy with anticancer and antioxidant qualities. The mushroom has been used as traditional medicines for the treatment of cardiovascular disease, tuberculosis, liver or heart diseases, bellyache, bloody gonorrhea, and diabetes. However, the limited production and market shortage have been attributed to the slow growth and the difficult collection of the fruiting body as well as the rare natural resources. The problem can be solved through the effective approach of submerged culture to produce a high bioactivity polysaccharide of P. igniarius. The project was proposed to investigate the effect of a surfactant on the production of polysaccharide in submerged culture of P. igniarius and their insulinotropic properties. Eight different surfactants including PEG series (4000, 6000), Tween series (20, 40, 80, 85), and Span series (20, 80) all at a concentration of 0.5 g/L were supplemented in turn to the basal medium in shake flasks. Among the various surfactants tested, Tween 80 exhibited the greatest exopolysaccharide production of 128.43 mg/L, and PEG 6000 showed the maximum biomass of 6.76 mg/mL. To find the optimal Tween 80 concentration for biomass and exopolysaccharide production, different Tween 80 levels (0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 g/L) were used in the medium. The maximal exopolysaccharide production of 132.76 mg/mL was achieved with the addition of 0.6 g/L of Tween 80 to the medium. The experimental results exhibited that the maximum of mycelia production in a stirred tank bioreactor was 3.01 mg/mL at Tween 80 0.2 g/L. In this study, their compounds, molecular weight, and protein content from fermentation product extracts were also tested. The average molecular weights of exopolysaccharide and intracellular polysaccharide were 1.715 × 106 Da and 4.87 × 105 Da, respectively. The protein contents of exopolysaccharide and intracellular polysaccharide were about 3.68% and 3.02%. The maximum RINm5F cell proliferations of exopolysaccharide and intracellular polysaccharide at 2 mg/mL were 142.3% and 120.07%, respectively. Cell proliferations of exopolysaccharide and intracellular polysaccharide increased with their concentrations. The maximum insulin secretion of exopolysaccharide at 2 mg/mL on RINm5F cell insulin was 0.615 μg/L.

Determining the amount of potentially bioavailable phenolic compounds and bioelements in edible mushroom mycelia of Agaricus bisporus, Cantharellus cibarius, and Lentinula edodes

Release of bioelements and phenolic compounds from edible mushrooms (Agaricus bisporus, Cantharellus cibarius, and Lentinula edodes) enriched with zinc, selenium, l-phenylalanine, alone and as a mixture was examined using a simulated human gastrointestinal digestion method. Due to the extensive amount of data obtained, in order to interpret them more precisely in the work, the methods of chemometric analysis (Cluster Analysis-CA and Principal Compenent Analysis-PCA) were additionally applied. The results showed mycelium of L. edodes has the best health-promoting properties and addition of mixture to the media increased significantly the synthesis of p-hydroxybenzoic and protocatechuic acid (267 and 16.3 mg/100 g d.w.). After extraction into artificial digestive juices, 97.4 mg/100 g d.w. p-hydroxybenzoic acid and 15.6 mg/100 g d.w. of protocatechuic acid were released. The greatest amounts of Se and Zn were extracted from enriched A. bisporus mycelium (32.3 and 342 mg/100 g d.w., respectively). This study confirmed that mycelium might prevent nutritional deficiencies in the diet through use of functional foods.

Production of natural colorants by liquid fermentation with Chlorociboria aeruginascens and Laetiporus sulphureus and prospective applications

The replacement of potentially hazardous synthetic dyes with natural dyes and pigments are of great interest for a sustainable economy. In order to obtain cost-efficient, environmentally friendly and competitive products, improvements in the cultivation and extraction of pigment-producing organisms and in dyeing processes are necessary. In our study, we were able to scale up the production of xylindein by Chlorociboria aeruginascens from 3 to 70 L bioreactor cultivations. We have identified important bioprocess parameters like low shear stress (150 rpm, tip speed <0.5 m/s) for optimal pigment yield (4.8 mg/L/d). Additionally, we have demonstrated the potential of laetiporic acid production by Laetiporus sulphureus in various cultivation systems and media, achieving dried biomass concentrations of almost 10 g/L with a 7 L bioreactor cultivation after 17 days. Extractions performed at 70°C and 15 min incubation time showed optimal results. To the best of our knowledge, we have described for the first time the use of this pigment in silk dyeing, which results in a brilliant hue that cannot easily be produced by other natural pigments.

Laetiporus sulphureus-fermented wheat bran enhanced the broiler growth performance by improving the intestinal microflora and inflammation status

This study investigates the effects of Laetiporus sulphureus–fermented wheat bran (LS) as a feed supplementation on the immunomodulative properties in broiler chickens. Crude phenolic compounds, crude polysaccharides, crude triterpenoids, and ergosterol were determined in LS water extracts. In animal experiments, 400 male broilers (Ross 308) were randomly assigned into 5 groups fed with a corn–soybean–based diet (control) and a control diet replaced with 5% wheat bran (WB), 10% WB, 5% LS, and 10% LS, respectively. Each group had 4 replicates and 20 birds per pen (total of 80 birds/treatment). The results showed that the 5% LS–supplemented group had significantly higher BW in the finisher phase (22–35 D). Better feed conversion ratio (P < 0.05) of LS-supplemented groups was observed in both the finisher phase and the overall experimental period. The LS-supplemented groups had significantly lower coliform counts in the ileum than the other treatment and control groups (P < 0.05). The results of serum immunoglobulin showed that LS supplementation significantly increased serum IgA concentration compared with the control and WB-supplemented groups (P < 0.05). Simultaneously, ileal IgA contents of the LS groups were significantly higher than in the WB and control groups (P < 0.05). Regarding proinflammatory cytokines, serum tumor necrosis factor alpha and IL-6 in the LS-supplemented groups were significantly lower than those in the 10% WB group (P < 0.05), whereas serum tumor necrosis factor alpha and IL-1β in the 5% LS group were significantly lower than in both the control and WB-supplemented groups (P < 0.05). An investigation on the effects of LS on immune-related genes in broiler showed that chickens supplemented with 5% LS had lower levels of liver and jejunum IL-1β and NF-κB mRNA compared with the control group and WB groups (P < 0.05). In conclusion, LS supplementation can potentially enhance growth performance of broilers by improving intestinal microflora and inflammation status.

Four lanostane-type triterpenes from the fruiting bodies of mushroom Laetiporus sulphureus var. miniatus

Two new 3,4-seco-lanostane-type triterpenes, named as 15α-hydroxy-3,4-seco-lanosta-4(28),8,24-triene-3,21-dioic acid (1), 5α-hydroxy-3,4-seco-lanosta-4(28),8,24-triene-3,21-dioic acid 3-methyl ester (2), and one new lanostane triterpene 15α-acetoxylhydroxytrametenolic acid (3) together with a known one versisponic acid D (4) were isolated from the fruiting bodies of Laetiporus sulphureus var. miniatus. Their structures were determined on the basis of extensive spectroscopic methods and comparison with reported data. All four compounds were evaluated for their cytotoxicities against five human cancer cell lines; however, none exhibited inhibitory effects.

Optimal conditions of mycelia growth of Laetiporus sulphureus sensu lato

Laetiporus sulphureus is an edible wood-rotting basidiomycete, growing on decaying logs, stumps, and trunks of many deciduous and coniferous tree species. This fungus produces relatively large striking yellowish or orange-coloured bracket-like fruitbodies. L. sulphureus is widely consumed as a nutritional food because of its fragrance and texture. In this study, two L. sulphureus strains, MFLUCC 12-0546 and MFLUCC 12-0547, isolated from Chiang Rai, Thailand, were investigated for optimal conditions of mycelia growth. Potato dextrose agar and malt extract agar were observed as the favourable medium for mycelia growth. The optimum pH and temperature for the mushroom mycelia were 6–8 and 25–30°C, respectively.

Fermentation characteristics in stirred-tank reactor of exopolysaccharides with hypolipidemic activity produced by Pleurotus geesteranus 5#

In this study, the hypolipidemic effect of exopolysaccharides (EPS) from Pleurotus geesteranus 5# fermenting liquor by the optimal culture conditions in a 5-L stirred-tank reactor was investigated. The hypolipidemic effect of the polysaccharide, investigated in streptozotocin induced diabetic mice, decreased plasma glucose, total cholesterol and triacylglycerol concentrations by 17.1 %, 18.8 % and 12.0 %, respectively. The results of the present investigation strongly demonstrate the potential of this polysaccharide to prevent hyperglycemia in the experimental animals. Under optimal culture conditions, the maximum concentrations of mycelial and EPS were 22.63 g/L after 7 d cultivation and 11.09 g/L after 10 d, respectively. Furthermore, the morphological parameters (i.e. mean diameter, circularity, roughness and compactness) of the pellets and the broth viscosity were characterized. It was proved that compactness of the pellet morphology (R²=0.963, p<0.01) was significantly and positively determined with mycelial biomass. Moreover, mean diameter (R²=93.3, p<0.01) and broth viscosity (R²=0.950, p<0.01) were significantly and positively determined with EPS content.

Optimization of exopolysaccharide production in submerged culture of Daedalea dickinsii and its antioxidant activity

The major nutrients, pH and temperature were evaluated for the exopolysaccharide (EPS) production by Daedalea dickinsii in submerged culture to derive an optimal medium composition and conditions as follows: 50 g/L maltose, 5 g/L soy peptone, 5 mM CaCl(2), at pH 6.0 and 28 °C. A purified EPS fraction was attained from gel filtration chromatography and its major molecular characteristics were determined. FT-IR spectral analysis revealed the prominent characteristic groups of polyhydric alcohols. GC analysis and NMR spectrum showed its major molecular composition of glucose and galactose. Furthermore, thermogravimetric analysis indicated its degradation temperature (T(d)) of 189 °C. The antioxidant activity of the EPS fraction showed a correlation with the molecular properties. It might be attributed to the functional groups in the EPS fraction, which can donate electrons to reduce the radicals to a more stable form or react with the free radicals to terminate the radical chain reaction.

Identification and functional analysis of the gene ste9 involving in Ebosin biosynthesis from Streptomyces sp. 139

Ebosin is a novel exopolysaccharide produced by Streptomyces sp. 139 with remarkable antirheumatic arthritis activity in vivo, and its biosynthesis gene cluster (ste) consisting of 27 ORFs has been identified. For functional analysis, one of the ste genes, ste9, was disrupted and then the gene complementation was performed. The resultant mutant Streptomyces sp. 139 (ste9(-)) produced polysaccharides with molecular weights of about 4.153 × 10(5) which is much smaller than that of Ebosin (9.03 × 10(5)). The complemented strain Streptomyces sp. 139 (pKC9c) showed recovery in the molecular weights of EPS produced (8.004 × 10(5)). As the theoretical protein product of ste9 is a chain length determinant (Wzz) homologue by sequence similarity, ste9 was cloned and expressed in E. coli 086:H2 (wzz(-)) for a complementation test. SDS-PAGE analysis showed that E. coli 086:H2 (wzz(-)) (pET30a-ste9) produced a modal chain length lipid polysaccharide (LPS) similar to that of the wild-type E. coli 086:H2. In addition, the expression of ste9 was able to restore the serum resistance of E. coli 086:H2 (wzz(-)) to almost the level of the wild-type strain. These results indicate that the ste9 gene is coding for a chain length determinant which plays an important role in Ebosin biosynthesis.

Anti-Inflammatory Effect of Ebosin on Rat Collagen-Induced Arthritis through Suppressing Production of Interleukin-1β, Interleukin-6 and Tumor Necrosis Factor-α

Reumatoid arthritis (RA) is an autoimmune disease which has been studied experimentally using a wide variety of animal models including collagen-induced arthritis (CIA). Using this CIA model we studied the therapeutic effects and mechanism of action of Ebosin, a novel exopolysaccharide produced by Streptomyces sp. 139, on arthritis. Ebosin at 200, 400 and 600 mg/kg/day was orally administered to rats respectively between day 10 and 30 after immunization with chicken type II collagen. With the treatment arthritic progression was remarkably suppressed. Levels of anti-type II collagen-specific antibody, IL-1β and TNF-α were significantly lower in the Ebosin-treated CIA rats compared with the untreated controls. In cultured fibroblast-like synoviocytes (FLS), remarkable suppression of IL-1β, TNF-α and IL-6 production was detected at both protein and mRNA levels after Ebosin administration. Ebosin also resulted in lower activities of IL-1β-converting enzyme and TNF-α-converting enzyme in FLS. Based on these results, it is concluded that development and progression of rat CIA can be significantly suppressed by orally-administrated Ebosin. The therapeutic effect may be attributed to its inhibition in the production of IL-1β, TNF-α and IL-6 in the CIA rats.

Successful large-scale production of fruiting bodies of Laetiporus sulphureus (Bull.: Fr.) Murrill on an artificial substrate

Laetiporus sulphureus is an edible wood-rotting basidiomycete fungus whose fruiting bodies contain substances with verified therapeutic evidences and large amounts of α-(1 → 3)-glucan which is used as an effective inducer of microbial α-(1 → 3)-glucanases. However, production of mature fruiting bodies of this species under artificially controlled conditions has not been reported until now. Here, we provide the first report of successful initiation and development of L. sulphureus fruiting bodies in large-scale experiments. Twelve Laetiporus strains were isolated from a natural habitat. A synthetic log production system with a substrate composed of a mixture of sawdust enriched with organic and inorganic additives was developed. It was found that shocking the fungus mycelium with cold water or low temperature was the only suitable method for forced fruiting of L. sulphureus strains. Primordia of two strains were initiated already after 5-6 days from induction, and after another 2 days, they began to develop into fruiting bodies. Carpophores appeared fastest on substrates with high organic supplementation (40-45 %) and a low moisture content (40 %). The resulting mature fruiting bodies reached a weight of 200-300 g. The method of cultivation presented in this paper opens the way to commercial production of this valuable basidiomycete.

Influence of rutin, FeSO4, Tween 80, aspartate and complex vitamins on synthesis of fungal exopolysaccharide

The influence of several components on exopolysaccharide (EPS) production and antioxidative activity (TEAC, Trolox-Equivalent Antioxidant Capacity) as well as their effects on the morphological development and cell viability of Phellinus sp. P0988 was determined. Rutin, FeSO(4), Tween 80 and complex vitamins were found to impose a stronger influence on EPS production and TEAC compared to their effects on the mycelia growth of Phellinus sp. P0988. The relative effects of these components on EPS activity were found to be different from that on EPS yield. Rutin and aspartate significantly affected EPS TEAC (P<0.05), while FeSO(4) and Tween 80 significantly influenced EPS production (P<0.05). These results yielded the optimum culture medium composition, with an EPS yield and TEAC of 6.2±0.2 g/L and 5.5±0.1 mM, respectively.

Exopolysaccharide of Laetiporus sulphureus var. miniatus downregulates LPS-induced production of NO, PGE₂, and TNF-α in BV2 microglia cells via suppression of the NF-κB pathway

Our previous study showed that the exopolysaccharide (EPS) of Laetiporus sulphureus var. miniatus was well characterized and prevented cell damage in streptozotocin-induced apoptosis. However, little is known about the molecular mechanisms underlying its anti-inflammatory effects. Therefore, we attempted in this study to determine whether EPS induces a significant inhibition of pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated murine BV2 microglia cells. Our results showed that EPS significantly inhibited LPS-induced pro-inflammatory mediators, such as nitric oxide (NO), prostaglandin E(2) (PGE(2)), and tumor necrosis factor-α (TNF-α), without any significant cytotoxicity. EPS also downregulated mRNA and protein expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α in LPS-induced BV2 microglia cells. Our data also revealed that EPS treatment significantly reduced translocation of nuclear factor-κB (NF-κB) subunit p65 and its DNA-binding activity in LPS-stimulated BV2 microglia cells. Furthermore, we confirmed by using proteasome inhibitor N-acetyl-l-cysteine (NAC), that the inhibition of NF-κB activity influenced the expression of pro-inflammatory genes in LPS-induced BV2 microglia cells. As expected, NAC suppressed the expression of iNOS, COX-2, and TNF-α by blocking proteasome-mediated degradation. Taken together, our data indicate that EPS inhibits the expression of pro-inflammatory mediators by suppressing NF-κB activity.

Polysaccharide fromGynura divaricatamodulates the activities of intestinal disaccharidases in streptozotocin-induced diabetic rats

During diabetes, structural and functional changes in the alimentary tract are known to take place resulting in an increased absorption of intestinal glucose and alterations in the activities of brush-border disaccharidases. To elucidate the effect of administrating polysaccharide fromGynura divaricata(PGD) on disaccharidase activities, the specific activities of intestinal disaccharidases, namely sucrase, maltase and lactase, were measured in streptozotocin-induced diabetic rats. Normal control and diabetic rats were treated by oral administration with PGD. Specific activities of intestinal disaccharidases were increased significantly during diabetes, and amelioration of the activities of sucrase and maltase during diabetes was clearly visible by the treatment with PGD. However, the increased activity of lactase during diabetes mellitus was remarkably alleviated by the administration of PGD only in the duodenum. Meanwhile, oral sucrose tolerance tests demonstrated that PGD alleviated the hyperglycaemia during diabetes mellitus, resulting from the amelioration in the activities of intestinal disaccharidases. The present investigation suggests that PGD exerted an anti-diabetic effect partly via inhibiting the increased intestinal disaccharidase activities of diabetic rats. This beneficial influence of administration of PGD on intestinal disaccharidases clearly indicates their helpful role in the management of diabetes.

An exopolysaccharide produced by the novel halophilic bacterium Halomonas stenophila strain B100 selectively induces apoptosis in human T leukaemia cells

Microbial exopolysaccharides (EPSs) are highly heterogeneous polymers produced by fungi and bacteria and have recently been attracting considerable attention from biotechnologists because of their potential applications in many fields, including biomedicine. We have screened the antitumoural activity of a panel of sulphated EPSs produced by a newly discovered species of halophilic bacteria. We found that the novel halophilic bacterium Halomonas stenophila strain B100 produced a heteropolysaccharide that, when oversulphated, exerted antitumoural activity on T cell lines deriving from acute lymphoblastic leukaemia (ALL). Only tumour cells were susceptible to apoptosis induced by the sulphated EPS (B100S), whilst primary T cells were resistant. Moreover, freshly isolated primary cells from the blood of patients with ALL were also susceptible to B100S-induced apoptosis. The newly discovered B100S is therefore the first bacterial EPS that has been demonstrated to exert a potent and selective pro-apoptotic effect on T leukaemia cells, and thus, we propose that the search for new antineoplastic drugs should include the screening of other bacterial EPSs, particularly those isolated from halophiles.