Feeding studies in rats with high protein fungus grown on natural gas

Preliminary feeding studies were conducted with a high protein fungus (Graphium sp.) grown on natural gas. The biomass, containing approximately 50% protein, is considered a potential source of single cell protein. In short-term (1-week) experiments, rats gained weight when fed semisynthetic diets containing up to 40% of the biomass, although growth was depressed at the higher levels. Rats lost weight but survived for this length of time when fed biomass alone. Chronic toxicity was tested in a 5-month study with diets in which the casein (20% by weight) of the semisynthetic diet was either partially or entirely replaced by the proteinaceous biomass. Rats fed these diets grew more slowly but appeared normal and healthy, and no pathological changes were observed at autopsy. Some of these rats were fed a standard laboratory diet for an additional 10-month observation period, and at autopsy, one cortical adenoma of the kidney was found in a rat originally fed the lower level of Graphium biomass.