Aureobasidium pullulans

Aureobasidium pullulans: A Comprehensive Reference on the Black Yeast and Its Bioactive Polysaccharides

1. Identity and Taxonomy

1.1 Scientific Classification and Nomenclature

Aureobasidium pullulans is a polymorphic, black-pigmented yeast-like fungus in the phylum Ascomycota, renowned for producing the exopolysaccharide pullulan and exhibiting remarkable environmental adaptability across diverse habitats. Belonging to the family Dothioraceae and order Dothideales, it displays dimorphic growth, alternating between unicellular yeast forms and multicellular hyphal structures depending on environmental cues such as pH and nutrient availability.

First described in 1866 as Dematium pullulans, the species forms part of a complex that includes closely related taxa like A. melanogenum and A. subglaciale, reflecting its genetic diversity with over 78 genomes sequenced to date. The organism has also been referred to historically under the synonyms Pullularia pullulans and Hormonema dematioides. Production of pullulan by the black yeast, Aureobasidium pullulans (formerly referred to as Pullularia pullulans), was initially identified by Bauer in 1938, with its characteristics and isolation process detailed couple of years later by Bernier.

Human disease cases involving Aureobasidium-complex organisms have been caused predominantly by A. pullulans var. melanigenum rather than A. pullulans var. pullulans. This distinction is important when evaluating the safety profile of supplement-grade strains. Aureobasidium melanogenum, formerly known as Aureobasidium pullulans var. melanogenum, is a ubiquitous black yeast-like fungus that includes strains causing human infections, which were previously classified as A. pullulans.

1.2 Ecology and Natural Habitat

This extremotolerant organism inhabits a wide range of ecological niches, from temperate soils and plant surfaces to extreme environments like glacial ice, hypersaline waters, and even aircraft fuel tanks, tolerating conditions such as up to 17% salinity, broad pH ranges, and extreme temperatures. Despite its prevalence in edible plant tissues and frequent environmental exposure, its broader role within microbiomes and potential relevance for human health remain underexplored.

The organism is isolated commonly from soil, water, and plant materials. A. pullulans is a polymorphic fungus present in three distinct forms: elongated branched septate filaments, large chlamydospores, and smaller, elliptical yeast-like cells. Research synthesis supports the view of A. pullulans as a safe, plant-beneficial symbiont with high value for sustainable crop protection and potential relevance for the One Health framework.

1.3 Principal Bioproducts and Common Supplement Forms

Two major classes of polysaccharide produced by A. pullulans are relevant to dietary supplement use:

• Pullulan (poly-α-1,6-maltotriose): A black yeast-like species particularly known for its biotechnological significance as a producer of the biodegradable extracellular polysaccharide (EPS) pullulan (poly-α-1,6-maltotriose). Pullulan is a neutral linear exopolysaccharide produced aerobically in starch and sugar media. It has been conferred with GRAS excipient status due to its lack of toxic, immunogenic, carcinogenic, and mutagenic properties. Its flexibility to chemical modification is a reason for its extensive application in cosmetics, food, and pharmaceutical industries.
• β-1,3-1,6-Glucan: A. pullulans extracellularly produces β-(1,3),(1,6)-D-glucan (β-glucan) under certain conditions. The β-glucan is known to be an immunomodulatory agent, and β-glucan-enriched A. pullulans cultured fluid (AP-CF) is used in supplements to maintain human health.

The black yeast Aureobasidium pullulans produces abundant soluble β-1,3-1,6-glucan — a functional food ingredient with known health benefits. For use as a food material, soluble β-1,3-1,6-glucan is produced via fermentation using sucrose as the carbon source. Commercially available supplement preparations include oral granules, gel sachets, and encapsulated powders. Two prominent supplement-grade strains in clinical research are designated AFO-202 and N-163.

Pullulan is not genetically modified and is commercially produced by a non-pathogenic and non-toxigenic strain of the organism using a liquid starch syrup as the fermentation substrate. Pullulan can be made into very thin films with high tensile strength and stability over a range of temperatures, making it an ideal material for the manufacture of empty capsules for encapsulating dietary supplements or as a coating for dietary supplement tablets.

2. Traditional and Historical Use

The production of pullulan was started by the Hayashibara Company, Japan in 1972. Since then pullulan has become the major polysaccharide produced by this company. Since 1976, it has been utilized as an additive and culinary component in Japan. Pullulan has been used extensively in the food industry as a food ingredient for over 20 years in Japan, and has Generally Regarded As Safe (GRAS) status in the USA.

The β-1,3-1,6-glucan fraction of A. pullulans does not have a documented history of traditional medicinal use predating modern fermentation biotechnology. Unlike mushroom-derived polysaccharides (such as lentinan from Lentinus edodes), A. pullulans-derived β-glucan is a product of industrial microbial fermentation developed in Japan in the late 20th century. Aureobasidium pullulans extracellularly produces a β-(1→3),(1→6)-D-glucan highly branched with β-(1→6)-glycosidic bonds with high efficiency. The β-(1→3),(1→6)-D-glucan contained in the cultured fluid of A. pullulans is approved as a food additive and is consumed as a health-promoting food in many countries.

Aureobasidium pullulans is an industrially important microorganism especially because of its capability to produce pullulan (poly-α-1,6-maltotriose). Pullulan is a commercially exploited biodegradable extracellular polysaccharide used in coatings and wrappings and as a food ingredient. The polysaccharide β-glucan produced by Aureobasidium is also commercially available.

3. Key Constituents and Active Compounds

3.1 Pullulan

Pullulan is an extracellular water-soluble homo-polysaccharide composed of linear maltotriose units interconnected via α-1,6-glycosidic linkages. These linkages endow pullulan with structural flexibility and high aqueous solubility. Although it is an α-d-glucan polysaccharide, it is not susceptible to mammalian amylases and thus can be used as a substitute to starch in food products such as low-calorie dietary fiber.

3.2 β-1,3-1,6-Glucan

Aureobasidium pullulans-derived β-glucan (AP-PG) consists of a β-(1,3)-linked glucose main chain and β-(1,6)-linked glucose branches and is taken as a supplement to improve health. Basically, an extraction process, such as hot-water extraction, is required for the production of β-(1→3),(1→6)-D-glucan-containing supplemental food derived from other organisms, but because A. pullulans secretes the glucan directly into its culture medium, it can be harvested without harsh extraction steps, facilitating water-soluble preparations. Unlike traditional beta-glucans that require extraction and have solubility challenges, A. pullulans-derived beta-glucans are water-soluble, simplifying oral administration.

Researchers have reported that if all β-1,6-branch side chains are removed from β-1,3-1,6-glucan by a chemically oxidized reaction, little anticancer activity is observed compared with that before the reaction, suggesting that β-1,3-glucan with β-1,6-branch enhances immunoactivity.

3.3 Other Metabolites

Other metabolites produced by A. pullulans that are used as medical supplements or additives in food include additional polysaccharide derivatives. Analyses consistent with the main component of certain A. pullulans extracts being aureobasidins — cyclic depsipeptide antifungal compounds — have also been described. However, aureobasidins are associated with biocontrol applications rather than dietary supplementation and are not currently used in consumer health products.

4. Mechanisms of Action

4.1 Immunoreceptor Engagement

Immune-mediated effects of glucan are primarily induced by pattern recognition receptors (PRRs), which include Dectin-1, CR3, TLRs, lactosylceramides, and scavenger receptors. Dectin-1 is the key beta-glucan receptor. The recognition and binding of TLR and Dectin-1 control the immune response by modulating the release of pro- and anti-inflammatory cytokines.

Beta-glucans activate a variety of immune cells, including macrophages, neutrophils, monocytes, natural killer cells, and dendritic cells, by binding to immune receptors such as Dectin-1, complement receptor 3 (CR3), and TLR-2/6. This pattern recognition receptor contains a single extracellular lectin-like carbohydrate recognition domain and a cytoplasmic tail with an immunoreceptor tyrosine-based activation-like motif (ITAM-like), which initiates intracellular signaling upon engagement of β-glucans. The recognition of β-glucans by Dectin-1 induces numerous cellular responses, including phagocytosis, the respiratory burst, the production of arachidonic acid metabolites, and the induction of a number of cytokines and chemokines.

Notably, A. pullulans-derived β-glucan has also been documented to act via receptor pathways independent of Dectin-1. The production of IFN-γ in mouse-derived splenocytes by A. pullulans-fermented β-d-glucan (AP–FBG) was not inhibited following treatment with an anti-dectin-1 neutralizing antibody. AP–FBG failed to activate dectin-1-mediated signaling pathways and failed to bind to dectin-1 — a pivotal receptor for 1,3-β-d-glucan. Together, AP–FBG induced cell activation via dectin-1-independent pathways. A so far unidentified beta-glucan receptor that induces an Akt/PI3K-dependent anti-inflammatory response also contributes to the metabolic and immune effects.

4.2 Trained Immunity and Epigenetic Reprogramming

Beta-glucan is a potent inducer of epigenetic and functional reprogramming of innate immune cells, a process known as "trained immunity" that improves the host's response to infections. Beta-glucan induces acquired immunity via histone modifications at gene promoters in human monocytes, which is accompanied by increased production of proinflammatory cytokines in response to a microbial challenge.

β-Glucan exhibits immune-modulating properties by binding to receptors like CR3 or Dectin-1 on innate cells, inducing the production of pro-inflammatory cytokines and altering epigenetic reprogramming of myeloid cells, initiating "trained immunity." Additionally, β-glucan activates lymphocytes, enhancing humoral immunity. These attributes collectively position β-glucan as a robust immune adjuvant.

4.3 TRAIL Induction and Antitumor Signaling

A β-glucan produced by Aureobasidium pullulans (AP-PG) consists of a β-(1,3)-linked main chain with β-(1,6)-linked glucose side residues. Various β-glucans consisting of a β-(1,3)-linked main chain, including AP-PG, are believed to exhibit anti-tumor activities, and anti-tumor activities of AP-PG in mice have been demonstrated. Stimulation with AP-PG has been shown to induce TRAIL expression in mouse and human macrophage-like cell lines. TRAIL is known to be a cytokine which specifically induces apoptosis in transformed cells, but not in untransformed cells.

4.4 Antiviral Gene Expression

The mRNA expression of virus sensors RIG-I (retinoic acid-inducible gene-I) and MDA5 (melanoma differentiation-associated protein 5) was strongly increased at 5 hours after stimulation with A. pullulans-produced purified β-(1→3),(1→6)-D-glucan in murine macrophage-derived RAW264.7 cells. Furthermore, the replication of influenza PR8 virus was significantly repressed by pre-treatment with this glucan. These findings suggest the increased expression of virus sensors is effective for the prevention of influenza by the inhibition of viral replication.

4.5 Tumor Microenvironment Modulation

Beta-glucans can also modulate the tumor microenvironment by bridging the innate and adaptive arms of the immune system and by altering the phenotype of immunosuppressive cells to make them immune-stimulatory, contributing to the effects against cancer.

5. Scientific Evidence by Area of Use

5.1 Immune Modulation

In vitro and animal evidence (strong preclinical basis): Various functionalities of β-1,3-1,6-glucan have been reported, including its immunomodulatory effect, particularly in the intestine. It also exhibits antitumor and antimetastatic effects, alleviates influenza and food allergies, and relieves stress. A highly purified soluble β-1,3/1,6-glucan derived from Aureobasidium pullulans (designated PPTEE-glycan) demonstrated robust immune stimulation in vitro, activated dendritic cells, and enhanced co-stimulatory markers, cytokines, and cross-presentation. Formulated as a microemulsion, it elevated immune responses in vivo, promoting antigen-specific antibodies and CD8+ T cell proliferation.

Human/clinical evidence (preliminary): In a pilot study, the specific metabolic and immune-related benefits of the AFO-202 strain and N-163 strain of black yeast Aureobasidium pullulans-produced beta-1,3-1,6-glucan were evaluated in healthy human subjects. Sixteen healthy Japanese male volunteers (aged 40 to 60 years) took part in this clinical trial. They were divided into four groups (n = 4 each): Group I consumed AFO-202 beta-glucan (2 sachets of 1 g each per day), one arm for 35 days and the other for 21 days; Group II consumed a combination of AFO-202 beta-glucan (2 sachets of 1 g each) and N-163 beta-glucan (1 sachet of 15 g gel each per day), one arm for 35 days and the other for 21 days. Decrease in HbA1c and glycated albumin (GA), significant increase of eosinophils and monocytes, and marginal decrease in D-dimer levels, decrease in neutrophil-to-lymphocyte ratio (NLR), with an increase in the lymphocyte-to-CRP ratio (LCR) and leukocyte-to-CRP ratio (LeCR) was observed in Group I between pre- and post-treatment. The evidence from this study is preliminary given the very small group sizes (n = 4 per arm) and the exploratory design.

5.2 COVID-19 and Respiratory Infection

Animal (preclinical) evidence: Oral administration of Aureobasidium pullulans-cultured fluid (AP-CF) enriched with β-(1→3),(1→6)-D-glucan exhibited efficacy in protecting mice infected with a lethal titer of the H1N1 strain of influenza virus. The survival rate of the mice significantly increased by AP-CF administration after sublethal infection. The virus titer in the mouse lung homogenates was significantly decreased by AP-CF administration.

Human/clinical evidence (pilot-level): In a pilot clinical study reporting the beneficial effects of beta-glucans derived from two strains — AFO-202 and N-163 — of Aureobasidium pullulans on the biomarkers for cytokine storm and coagulopathy in COVID-19 patients, a total of 24 RT-PCR positive COVID-19 patients were recruited and randomly divided into three groups: a control group (n = 8) on standard treatment; a second group (n = 8) on standard treatment plus AFO-202 beta-glucan; and a third group (n = 8) on standard treatment plus combination of AFO-202 and N-163 beta-glucans, all for 30 days. There was no mortality or requirement of ventilation of the subjects in any of the groups. Supplementation with the beta-glucans produced by the AFO-202 and N-163 strains helped to maintain the major biomarkers of clinical severity and mortality of COVID-19, viz., IL-6, D-dimer, and NLR over 15 and 30 days, compared to those who underwent standard care alone.

A second study evaluated AFO-202 and N-163 beta-glucans against COVID-19 inflammatory markers. A total of 40 RT-PCR positive COVID-19 patients were divided into two groups: a control group (n = 22) receiving standard treatment and a treatment group (n = 18) receiving standard treatment plus a combination of AFO-202 and N-163 beta-glucans for 15 days. The C-reactive protein (CRP), which declined from 33.95 mg/l to 5.07 mg/l in control and from 33.95 mg/l to 5.64 mg/l in the treatment arm on Day 7, increased to 14.6 mg/l in the former, while it continued to be under control in the treatment arm at 5.68 mg/l on Day 15.

Evidence strength: These COVID-19 studies are small (n = 24 and n = 40), open-label or multiple-arm pilot trials, conducted primarily in India. Being pilot studies with limited numbers of subjects, upon validation in larger multi-centric clinical trials, these nutraceutical agents may be considered as continuous oral supplemented adjuncts for prophylaxis and management of COVID-19 or post-COVID sequalae. Results are therefore preliminary and not sufficient to establish clinical efficacy.

5.3 Glucose Metabolism and Glycemic Regulation

Human evidence (exploratory): Based on the beneficial effects of the AFO-202 strain of black yeast Aureobasidium pullulans-produced beta-1,3-1,6-glucan in balancing blood glucose and immune enhancement, and that of the N-163 strain of the same species in lipid metabolism and immune modulation, a pilot study evaluated their specific benefits in healthy human subjects. The AFO-202 arm showed a decrease in HbA1c and glycated albumin levels over 21–35 days.

Animal evidence: Repeated oral administration of β-glucans derived from the AFO-202 and N-163 strains of A. pullulans, for 28 days, resulted in lower triglyceride and NEFA levels in male KKAy mice than before the start of treatment. There were no significant differences in blood glucose, HbA1c, triglycerides, LDL, and HDL cholesterol levels in the same study, indicating modest and selective effects on lipid parameters. Evidence strength: Preliminary; human data are from small exploratory trials only.

5.4 Liver Health (Non-Alcoholic Fatty Liver Disease / NASH)

Animal evidence: The A. pullulans-derived β-glucan (AP-PG), consisting of a β-(1,3)-linked glucose main chain and β-(1,6)-linked glucose branches, is taken as a supplement to improve health. Results suggest the possibility that oral administration of AP-PG is effective in preventing the development of non-alcoholic fatty liver disease (NAFLD). Mitigation of lipotoxicity-associated inflammatory cascades in a mouse study has also been reported. Another study done in an animal model of non-alcoholic steatohepatitis (NASH) showed a decrease in liver inflammation and accumulation of F4/80+ cells (macrophages associated with inflammation) in the liver. Evidence strength: Preclinical (animal) only; no peer-reviewed human trials specifically targeting NAFLD/NASH have been published as of the date of this article.

5.5 Antitumor and Antimetastatic Activity

Preclinical evidence: Various β-glucans consisting of a β-(1,3)-linked main chain, including the A. pullulans-derived glucan AP-PG, are believed to exhibit anti-tumor activities, and anti-tumor activities of AP-PG in mice have been demonstrated. Stimulation with AP-PG induces TRAIL expression in mouse and human macrophage-like cell lines. Intratumoral administration of a purified A. pullulans-derived β-glucan formulation in tumor-bearing mice induced notable tumor regression, which was linked to the activation of immunosuppressive cells.

Human/clinical evidence: No published controlled human trials specifically addressing cancer endpoints with A. pullulans-derived β-glucan were identified in the literature reviewed. Research highlights the potential of high-purity Aureobasidium pullulans-derived β-glucan as a promising immune adjuvant and suggests that the high purity of β-glucan promotes sufficient immune cell stimulation. These results indicate that it can be utilized in the medical and vaccine industries. Evidence strength: Predominantly in vitro and animal-based; human evidence is lacking.

5.6 Duchenne Muscular Dystrophy (DMD)

Human evidence (small open-label studies): Several pilot clinical studies have examined the N-163 strain of A. pullulans-produced β-glucan in patients with Duchenne muscular dystrophy. Medical Research Council (MRC) grading showed slight improvement in muscle strength in 12 out of 18 patients (67%) in the treatment group and four out of nine (44%) subjects in the control group. Supplementation with the N-163 beta-glucan food supplement produced beneficial effects: a significant decrease in inflammation and fibrosis markers, increase in serum dystrophin, and slight improvement in muscle strength in DMD subjects over 45 days.

The clinical results of another study showed that supplementation with the N-163 beta-glucan food supplement produced disease-modifying beneficial effects: a significant decrease in inflammation and fibrosis markers such as IL-6, IL-13, and transforming growth factor-beta; increase in dystrophin; and improvement in muscle strength in DMD subjects over a period of 45 days.

A 6-month non-randomized open-label linear clinical trial reported that the N-163 strain of A. pullulans-produced beta-glucan food supplement improved MRC grading in 91.6% of patients, with modest improvements in 6-minute walk test (6MWT) and North Star Ambulatory Assessment (NSAA) score. The limitations of the study include uneven distribution of subjects, broad age range (5–19 years), and short follow-up (only 45 days); improvements in muscle function over the course of the study showed variability that may have been due to the level of sensitivity to change of functional assessments during disease progression. Evidence strength: Preliminary; single-centre, open-label, small studies requiring validation in multi-centre randomized controlled trials.

5.7 Allergy and Atopic Conditions

Preclinical evidence: Inhibitory effects of water-soluble, low-molecular-weight β-(1,3–1,6)-d-glucan purified from Aureobasidium pullulans GM-NH-1A1 strain on food allergic reactions in mice have been reported in International Immunopharmacology. Clinical studies have reported the antiallergic and triglyceride-reducing effects of β-1,3-1,6-glucan, which are indicators of improvement in lifestyle-related diseases. Evidence strength: Preclinical data for food allergy; antiallergic effects reported in clinical settings but detailed peer-reviewed human trial data were not extractable from available sources in this review.

5.8 Bone Health

Animal and in vitro evidence: The wound healing properties of β-glucans isolated from Aureobasidium pullulans were studied in human fetal dermal fibroblast cell lines. β-Glucan-mediated transforming growth factor (TGF-β1) showed increased procollagen production. Effects of polycan (a glucan isolated from Aureobasidium pullulans) were evaluated in different osteoporosis model rats. A significant increase in bone mineral density of the femur, tibia, and L6, as well as an increase in calcium bioavailability and a decrease in calcium secretion in ovariectomy thyroparathyroidectomy rat models, were observed. Evidence strength: Animal and in vitro only; no human controlled trials identified for bone endpoints.

5.9 Parkinson's Disease

Human pilot evidence: A preliminary clinical study examined the AFO-202 strain of A. pullulans-produced β-glucan in Parkinson's disease patients. The mean UPDRS score at baseline was 43.25 ± 13.75 and decreased to 40 ± 13.65 (p value = 0.5) after 90 days. Improvements were observed in cognition, walking and balance, postural stability, and constipation scales. The mean total cholesterol decreased from 190.67 ± 31.65 mg/dL to 160.16 ± 28.69 mg/dL. Mean triglyceride levels at baseline decreased from 187.50 ± 218.81 to 112 ± 59.66 mg/dL. There were no serious adverse effects in any of the study subjects. Evidence strength: Very preliminary (preprint-level pilot study, non-significant primary UPDRS outcome); findings are hypothesis-generating only.

5.10 Broader Metabolic and Lifestyle Disease Areas

Reported functions of A. pullulans-derived β-1,3-1,6-glucan include reducing the risk of lifestyle-related diseases by protecting the intestinal mucosa, reducing fat, lowering postprandial blood glucose, promoting bone health, and healing gastric ulcers. These effects have been described predominantly from preclinical and Japanese functional food literature; rigorous large-scale human trials corroborating each of these specific endpoints remain limited or unpublished in the peer-reviewed literature accessible at the time of this writing.

6. Body Systems Associated with Aureobasidium pullulans Bioactives

• Immune system: Innate and adaptive immunity via macrophage, dendritic cell, NK cell, and T-cell activation; trained immunity induction.
• Gastrointestinal system: Immunomodulatory effects particularly in the intestine and gut-associated lymphoid tissue (GALT).
• Metabolic system: Glucose and lipid metabolism regulation; anti-lipotoxic effects in animal models.
• Hepatic system: NAFLD/NASH prevention in animal models.
• Musculoskeletal system: Bone mineral density (animal models); exploratory human studies in DMD.
• Cardiovascular system: Reduction of D-dimer and coagulopathy markers in pilot COVID-19 studies; lipid-lowering effects.
• Neurological system: Exploratory studies in Parkinson's disease and multiple sclerosis (pilot-level only).
• Dermal system: Wound healing and collagen synthesis in vitro.

7. Dosage Forms and Dosages Reported in Studies

The following dosages appear in the cited peer-reviewed and preprint literature. They represent study protocols and are not recommended dosages.

• AFO-202 β-glucan (granule form): 2 sachets of 1 g each per day (total 2 g/day) for 21 to 35 days in healthy volunteers.
• N-163 β-glucan (gel form): 1 sachet of 15 g gel per day in combination with AFO-202 in healthy volunteers.
• N-163 β-glucan (DMD study): One sachet of N-163 beta-glucan (8 g gel, containing 48 mg of active ingredient) once daily along with conventional treatment.
• COVID-19 combination arm: AFO-202 beta-glucan at 3 g per day (1.0 g granule with each meal) in combination with N-163 beta-glucan at 10 g per day (10 g gel in a sachet with 90 mg of β-1,3-1,6-glucan, with one of the meals every day).
• Animal models (KKAy mice): AFO-202 beta-glucan at 200 mg/kg/day; N-163 beta-glucan at 300 mg/kg/day for 28 consecutive days.

The β-(1→3),(1→6)-D-glucan contained in the cultured fluid of A. pullulans is approved as a food additive and is consumed as a health-promoting food in many countries. β-Glucan is one of the food-grade feedstocks approved publicly by the Taiwan Food and Drug Administration and the Japanese Ministry of Health, Labour and Welfare, as well as a GRAS food additive approved publicly by the U.S. Food and Drug Administration.

8. Safety Considerations

8.1 General Safety and GRAS Status

Pullulan has been Generally Recognized as Safe (GRAS) by the US Food and Drug Administration (FDA) for use in foods. The A. pullulans strain used in commercial pullulan production is non-toxigenic and has been selected by traditional techniques; the strain is not the product of genetic modification using recombinant technologies. The production strain has a high yield of pullulan and low production of black pigment (melanin).

The A. pullulans-produced beta-glucan has been in human consumption for more than two decades and its safety has been established in healthy volunteers apart from in conditions such as autism spectrum disorder (ASD), NASH, COVID-19, diabetes, and dyslipidaemia.

8.2 Opportunistic Infection Risk

While supplement-grade strains are described as safe for healthy individuals, the organism in nature carries a documented potential for opportunistic pathogenicity in immunocompromised hosts. Aureobasidium pullulans is a saprophytic fungus widely distributed in the environment and used in a wide range of industrial applications. Like many saprophytic fungi, in the right host A. pullulans can be an opportunistic human pathogen and has been reported to cause hypersensitivity pneumonitis, subcutaneous infection, peritonitis, and rarely disseminated infection. Specifically, a case of Aureobasidium pullulans central catheter-related fungemia and septic pulmonary emboli was successfully treated, illustrating that in the right host conditions, the organism can be an opportunistic human pathogen. It is important to note that the supplement-grade beta-glucan preparations are purified fermentation products, not live organisms; however, this background ecology is relevant context for immunocompromised populations.

8.3 Respiratory Sensitization

Environmental Aureobasidium pullulans is a potentially pathogenic black yeast-like and halotolerant fungus associated with infections and pulmonary problems, especially allergy due to respiratory irritation mediated by cell-wall components (e.g., glycoproteins, beta-glucans) in patients with respiratory diseases, children, older people, and immune-compromised patients. This concern relates to environmental or occupational aerosolized fungal exposure, not to oral supplementation.

8.4 Adverse Events Reported in Clinical Studies

In one pilot study in Parkinson's disease, one subject developed loose stools that were controlled with medication. There were no serious adverse effects in any of the other study subjects. Across the small-scale COVID-19, DMD, and healthy volunteer trials reviewed, serious adverse events were not reported, though sample sizes are insufficient to characterize rare adverse events.

8.5 Conflict of Interest Considerations in the Evidence Base

Several key authors in the published literature declare employment by Aureo Co., Ltd., the commercial entity marketing beta-glucan-containing Aureobasidium pullulans-cultured fluid and its derivatives. A substantial proportion of the clinical evidence base originates from a small research group with consistent industry ties, which is a material limitation on interpreting the independence and generalizability of the findings. Replication by independent groups is necessary before any firm clinical conclusions can be drawn.

8.6 Evidence Gaps and Overall Evidentiary Assessment

A comprehensive, multi-centric clinical study should be conducted to unravel the potential of this orally consumable, safe, and allergen-free food supplement as a drug adjuvant. This outcome warrants larger clinical trials to understand the mechanisms and explore the potentials of these safe food supplements in prevention and prophylaxis of diseases due to dysregulated glucose and lipid metabolism and infections such as COVID-19. As of the current literature, the most robust human evidence exists for effects on inflammatory and coagulopathy biomarkers in COVID-19 (pilot level); effects on skeletal muscle parameters in DMD (open-label pilot level); and effects on immune and metabolic markers in healthy volunteers (very small exploratory randomized trials). Preclinical evidence is substantially broader. Large-scale, independent, placebo-controlled randomized controlled trials are absent across all primary indication areas.

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