Toxicological evaluation of protein powder derived from Cupriavidus necator

Abstract

Microorganisms have the potential to produce nutrient‐rich products that can be consumed as food or feed. The protein‐rich powder derived from heat treatment of the whole‐cell biomass of polyhydroxybutyrate‐deficient Cupriavidus necator, a metabolically versatile organism that uses elements found in the air, is an example of such a product. To assess the safety of the protein powder for use as a nutritional ingredient in human food, in accordance with internationally accepted standards, its genotoxic potential and repeated‐dose oral toxicity were investigated. A bacterial reverse mutation test, an in vitro mammalian chromosomal aberration test, and an in vivo mammalian micronucleus test were performed. No evidence of mutagenicity or genotoxicity was found. Additionally, a 90‐day repeated‐dose oral toxicity study in rats was completed, in which a total of 100 male and female Wistar rats were exposed by gavage to daily doses of 1000, 2000, or 3000 mg/kg bw/day of the test material. Following 90 days of continuous exposure, no mortality or treatment‐related adverse effects were observed and no target organs were identified. Therefore, a no observed adverse effect level was determined at 3000 mg/kg bw/day, the highest dose tested.

CO2-based production of phytase from highly stable expression plasmids in Cupriavidus necator H16

“…In 2021, EFSA authorized C. necator for the production of food additives, flavorings and food enzymes on the European market [ 53 ]. Indeed, studies testing C. necator H16 PHB − 4 as animal feed were already conducted [ 20 , 54 ] and none of them reported any toxic ingredients in the prepared biomass. Since no pathogenic strains are known, a direct feed of C. necator biomass containing AppA to pig or poultry may be conceivable in the future.…”

“…However, due to concerns about accumulation of undigestible polyhydroxybutyrate (PHB) and elevated nucleic acid levels, which could potentially result in increased uric acid levels in consumers, C. necator was largely dismissed as a protein source for human and animal consumption. In recent years, the growing awareness of the climate crisis and the demand for eco-friendly high-quality protein production, coupled with C. necator ’s capacity to thrive in mineral-based media using CO 2 as a carbon source, have revived interest in its application as food and feed component [ 1 , 20 ]. To valorize C. necator for the feed applications, we decided to produce the E. coli derived phytase AppA (AppA Ec ) free of antibiotics, using novel, highly stable expression vectors in the PHB negative PHB − 4 strain.…”