Isolation of Starch Degrading Spoilage Bacteria from ‘Ogi’ (Fermenting Maize Starch)

Abstract

Fermented maize starch known as ‘Ogi’ (Yoruba) or Akamu (Igbo) is a popular staple food and most popular traditional weaning food in West African countries. Its consumption by convalescents in these regions call for a safe product, free of pathogens and any potentially hazardous micro-organisms. The microorganisms associated with the spoilage of ‘ogi’ (fermented maize starch) porridge were isolated after seven day of fermentation. ‘Ogi’ off odour was first noticed at the 4th day of fermentation. Of all these bacteria and yeasts isolated, only bacteria could hydrolyze the starch in the ogi porridge and they were identified as Bacillus magaterium and Bacillus subtilis. The amylase activities of these organisms were studied under different temperature (20-80^°C) and pH (2-8). The optimum temperature of both organisms was 40^°C and optimum pH for Bacillus megaterium was four and that of Bacillus subtilis was two. Bacillus megaterium has higher amylase activity and thus was used to cause spoilage of sterile ogi porridge. The consistency of ‘Ogi’ change (liquefy) on the fourth day instead of the normal seven-day duration. In other to prevent ‘Ogi’ spoilage by Bacillus megaterium, a preservative, sodium benzoate was added to the sterile 'ogi' containing the inoculum, it was noticed that ‘Ogi’ aroma and colour remained the same but there was a little change in the consistency after seven days.