Patent ID: 7119228

Claim:
A process for producing methionine, comprising: a) adding at least one compound selected from the group consisting of potassium carbonate; potassium bicarbonate; and potassium hydroxide; to a solution containing 5-(β-methylmercaptoethyl)hydantoin to hydrolyze said 5-(β-methylmercaptoethyl)hydantoin and to thereby obtain a solution containing methionine; b) saturating the solution containing methionine of step a) with carbon dioxide to precipitate the methionine, and separating the precipitated methionine from a first filtrate; c) dividing said first filtrate into a first part and a second part, returning the first part to the reaction of step a), and transferring the second part to step (d); d) heating the second part of the first filtrate to a temperature above 200° C. for a period of time and at a pressure sufficient to obtain a heat-treated filtrate, saturating the heat-treated filtrate with carbon dioxide to precipitate the methionine and potassium bicarbonate, and separating the precipitated methionine and potassium bicarbonate from a second filtrate; and e) either discarding the second filtrate or returning it to the reaction of step a).