During World War I, the Germans needed glycerol to make nitroglycerin, which is used in the production of explosives such as dynamite. Before the war, the Germans had imported their glycerol, but this impact was prevented by the British naval blockade during the war. The German scientist Carl Neuberg (1877–1956) knew that trace levels of glycerol are produced when Saccharomyces cerevisiae is used during the alcoholic fermentation of sugar. He sought and developed a modified fermentation process in which the yeast would produce significant quantities of glycerol and less ethanol. The production of glycerol was improved by adding 3.5 percent sodium sulfite at pH 7 to the fermentation process, which blocked one chemical reaction in the metabolic pathway. Neuberg’s procedure was implemented with the conversion of German beer breweries to glycerol plants. The plants produced 1,000 tons of glycerol per month. After the war ended, the production of glycerol was not in demand, so it was suspended.