Screening and Characterization of Baker's Yeast in Agricultural Waste

Bread is a staple food in Nigeria and a popular bakery product. It is made majorly of wheat flour, sugar, salt, yeast and water. Yeast is used primarily for the purpose of dough leavening. They are commonly isolated from sugar rich environments. The aim of this research was to isolate and characterize yeasts with bakery properties from fruit wastes (peels). The peels used were from mango, banana, watermelon and cyncamor. The peels were washed, cut to pieces, serially diluted and an aliquot spread plated on Yeast extract peptone dextrose agar. Distinct colonies were picked, screened for bakery yeast properties and selected isolates were characterized. The selected isolates were also subjected to stress tolerance tests. Isolates Ma1, Ma2, Ma3, Ba1, Ba2, Ba3, Wa1, Wa2, Wa3, Cy1, Cy2 and Cy3 were observed for sugar fermentation, hydrogen sulphide production and flocculation. Commercial yeast served as control. Ma1 and Ba1 were selected based on their performance. They utilized glucose, maltose, lactose, sucrose, fructose and xylose while the control could not utilize lactose, maltose and xylose. Ma1 and Ba1 produced mild hydrogen sulphide and showed reseasonable flocculation. Moderate growth was observed on high ethanol, salt and glucose concentrations, showing higher stress tolerance than the control. They were identified as Pichia Kudriavzevii. The result from this work showed that bakery yeast can be isolated from wastes (non food materials) and that Picha Kudriavzevii (a non conventional yeast) can also be useful in bakery industry.