Egg yolk hydrolysis Egg yolk emulsion was prepared from a fresh egg, which was washed well in soap solution, rinsed and surface sterilized with 70% ethanol for 5 minutes. The egg was then flamed, broken aseptically, yolk separated into a sterile graduated cylinder and diluted to 40% v/v with sterile water. An aliquot of 10 ml of the egg yolk was incorporated into 100 ml molten nutrient agar (cooled to 55 °C) prior to pouring into the plates. The medium was spot cultured and incubated for three days at 28 °C. Production of turbid zone of free fats around the colonies was considered positive [12].