Soluble fractions of sonicates derived from cell suspensions of some bacteria and yeasts, which contaminate palm sap, enhanced nitrosamine formation when each fraction was incubated, under sterile conditions, at a pH of 7.0 +/- 0.2, with either diphenylamine, dimethylamine or diethylamine and sodium nitrite and glucose as substrates. The intrinsic factor in the extracts, which was responsible f...