Rhizomucor pusillus mycelium
What studies say about health-related effects

From a physiology and nutrition angle, what matters is what was measured in people or in a digestibility model: protein and fibre content, amino-acid quality (DIAAS), the rise of plasma amino acids after a meal, and GI tolerance plus selected biomarkers under repeated intake. For CBS 143028 the evidence base is narrow but concrete — and that is where this review starts.

1. What was studied?

The material is dried, milled mycelium biomass of R. pusillus CBS 143028, produced by fermentation and heat-inactivated. The EFSA NDA Panel assessed it in Safety of Rhizomucor pusillus biomass powder as a novel food (EFSA Journal 2025; e9707). In parallel, Wageningen Food & Biobased Research published two human reports commissioned by The Protein Brewery: TOMMY (tolerance and biomarkers, DOI 10.18174/547220, NCT04590768) and MyDi (postprandial amino-acid profiles, DOI 10.18174/554344, NCT04819789). A separate article covers the EU authorisation 2026/1507 — here the focus is physiology and nutrition.

2. Composition: protein, fibre, fat, micronutrients

Per e9707 the biomass is mainly ~50.8 g/100 g crude protein (Kjeldahl, N×6.25), ~31% dietary fibre and ~5% fat. Sum of anhydrous amino acids (“true protein”) is about 40.2 g/100 g — a meaningful gap versus crude protein because some nitrogen is non-protein.

Micronutrients (five batches): choline roughly 408–590 mg/100 g; riboflavin ~0.13–0.21 mg/100 g; vitamin B₆ ~0.26–0.47 mg/100 g; zinc ~4.7–6.2 mg/100 g; iron ~1.9–4.4 mg/100 g; phosphorus and magnesium at levels typical of microbial biomass. Folate and vitamin D₃ were below quantification limits in the tested batches. Antinutrients: phytic acid ~1.04%; oxalate and trypsin inhibitors below LOQ. The Panel judged that NF intake would not substantially raise phytate exposure versus the background diet.

3. Protein quality: DIAAS 61%

True ileal digestibility of indispensable amino acids was measured with the tiny-TIM system on one NF batch. Comparison with the FAO (2013) pattern for children aged 6 months–3 years yielded DIAAS 61%, with leucine as the limiting amino acid. Below 75%, FAO does not class the protein as “good quality”. The NDA Panel still found intake acceptable within a varied EU diet provided the mycelium is not the sole protein source when overall protein intake is low.

4. MyDi: postprandial plasma amino acids (humans)

MyDi was a randomised, double-blind crossover trial (n=12 healthy adults). Test meals provided 20 g protein from Fermotein dry, Fermotein wet, Fermotein wet modified (autolysis), or commercial Quorn mycoprotein. Products were not cooked — served as porridge. Nineteen free amino acids were measured in plasma for up to 5 h, plus glucose and insulin.

• Highest TAA/EAA response: Quorn.
• Intermediate: Fermotein dry — AUC and peak significantly higher than wet forms.
• Low / almost flat: Fermotein wet and wet modified — despite an autolysis step intended to improve digestibility.

Authors conclude that drying (powder) improves amino-acid availability versus wet biomass from the same fermentation, and that wet forms need further processing if they are to serve as a protein source. Quorn — a commercial product after years of optimisation — outperformed dry Fermotein; the design did not include a whey benchmark.

5. TOMMY: GI tolerance and biomarkers at 11 g/day

TOMMY (n=24, parallel, double-blind): 18 consecutive days of lunch with ~11 g Fermotein powder vs a macronutrient-matched control (whey + wheat bran). Primary: GI symptoms (VAS). Secondary: Hb, Fe, ferritin, glucose, insulin, cholesterol, ALAT/ASAT/GGT, leukocytes, creatinine, zonulin, blood pressure.

• Serious GI complaints: none; overall discomfort scores low.
• After day 1: higher (but mild) bloating (~24/100) and flatulence (~26/100) vs control; differences tended to shrink over 18 days.
• Stool form (Bristol) and frequency: no meaningful between-group differences.
• Biomarkers: most unchanged vs control. Exception: Hb — decrease in the Fermotein arm vs control (mean ~−0.4 vs −0.1 mmol/l; p=0.01); all 12 active-arm participants fell (−0.1 to −0.7). Fe and ferritin did not differ significantly. Authors speculate about siderophores (e.g. rhizoferrin) and urge follow-up — especially for vegetarians.
• Systolic blood pressure: downward trend (p=0.09) — not significant; not evidence of a hypotensive effect.

6. What is missing for this strain

No peer-reviewed RCTs were found for R. pusillus CBS 143028 / Fermotein showing gut-microbiota shifts, glycaemic control in clinical populations, body-weight reduction, lipids as a primary endpoint, or MPS equivalence versus animal diets. β-glucan / microbiota literature on mycoprotein mainly concerns Fusarium venenatum — extrapolating to Rhizomucor would be speculation. Safety (negative genotoxicity, high 90-day NOAEL in Scaife et al. 2025, low clinical allergy risk) is use-context, not benefit evidence.

7. Bottom line

For R. pusillus CBS 143028 mycelium, the health-nutrition literature mainly documents composition, moderate protein quality (DIAAS 61%), better postprandial amino-acid availability from the dry versus wet form, and short-term GI tolerance at 11 g/day with an Hb signal to watch. It does not document metabolic or gut clinical benefits. Novel-food authorisation (EU 2026/1507) confirms safety under the authorised uses — that is not the same as an authorised health claim under Regulation (EC) No 1924/2006.

Primary sources

1. EFSA NDA Panel (2025). Safety of Rhizomucor pusillus biomass powder as a novel food… EFSA Journal; e9707
2. Esser et al. (2021). Postprandial amino acid profiles… MyDi study. WUR Report 2187
3. Esser et al. (2021). Impact of daily Fermotein consumption… TOMMY study. WUR Report 2153
4. NCT04819789 — MyDi
5. NCT04590768 — TOMMY
6. Scaife et al. (2025). Subchronic toxicity… J Appl Toxicol
7. Scaife et al. (2023). In silico and in vitro safety assessment… Food Chem Toxicol
8. FAO (2013). Dietary protein quality evaluation… Food and Nutrition Paper 92