Optimization of Amylases Production from Fonio Using Central Composite Design

Abstract

This study aimed to optimize the production of amylases from grains of fonio which are of two main types; Digitaria exilis popular referred to as white fonio or Acha and Digitaria iburua, commonly known as black fonio or Iburu. These are with a view of determining the suitability of amylases from these grains as a suitable alternative to amylases from other tropical cereals. Whole grains of white and black fonio (100 g) were steeped in water and water containing phosphate salt for 24 h at room temperature and germinated in a locally constructed malting chamber for six (6) days. The most appropriate conditions of pH and temperature for the induction of amylases in these grains were selected based on central composite design (CCD). Amylase activities of crude extracts from harvested malts of white and black fonio were measured by assaying the reducing sugar released from starch using dinitrosalicylic acid method and soluble proteins were quantified by Bradford method. The induced amylases are a function of the days of germination as the highest amylase activity was obtained on second day (48 h) of germination with 17, 498 U/mg protein and 24, 337 U/mg protein for white and black fonio respectively. CCD suggested a cubic and quadratic model with range of values factor A (pH) and B (temperature) as limiting factors because any variation in themwill greatly affect the induced amylases which is the response. Specific activity (response) for both white and black fonio grains increases with an increase in both pH and temperature until further increase in these two factors resulted in a decrease in their responses (specific activity). CCD indicated that pH 6.5 and 22.5 °C were the best conditions for amylase production in black fonio grain while pH 6.0 and 20 °C were obtained for white fonio grains. The study concluded that grains of white and black fonio are rich sources of amylases and they could be of high value in various biotechnological applications.