Bacterial fermentation of cheese whey for production of a ruminant feed supplement rich in crude protein

Abstract

A simple and efficient process for the production of a ruminant feed supplement, rich in crude protein (defined as total N x 6.25), by bacterial fermentation of cheese whey has been developed. The lactose in unpasteurized whey is fermented to lactic acid by Lactobacillus bulgaricus at a temperature of 43°C and pH 5.5. The lactic acid produced is continually neutralized with ammonia to form ammonium lactate. The fermented product is concentrated by evaporation to a solids content of about 70% and adjusted to pH 6.8 with additional ammonia. The concentrated product contains about 55% crude protein. Approximately 6 to 8% of the crude protein is derived from bacterial cells, 17% from whey proteins, and 75 to 77% from ammonium lactate. The efficiency of conversion of lactose to lactic acid usually exceeds 95%. The fermentation time is greatly reduced upon the addition of 0.2% yeast extract or 0.1% corn steep liquor as a source of growth factors. Whey containing lactose at concentrations up to 7% can be fermented efficiently, but at higher concentrations lactose is fermented incompletely. The process has been scaled up to a pilot plant level, and 40 tons of concentrated product were produced for animal feeding trials, without ever encountering putrefactive spoilage.