Abstract: Method and apparatus is described for the microbiological production of single-cell protein making use of ethanol as a base material thereby allowing the protein produced to be used for human consumption.The process involves the cultivation of ethanol activated yeasts at temperatures between 20.degree. and 40.degree. C. under aerobic conditions in a fermentation column containing a dilute nutrient medium having a pH value in the range 2.5 to 5 containing nutrient salts, acid phosphate and nitrogen-containing substances in which the nutrient medium is continuously circulated into and through and out of the fermentation column and at each re-entry into the column is introduced tangentially into a zone which is oxygen enriched using oxygen gas molecules in the range 1 to 7 mu to form a bio-mass which can be separated and dried to form a protein product.