The role of Staphylococcus species in the production of iru during the fermentation of African locust beans (Parkia biglobosa)

Abstract

Staphylococcus spp. are regularly isolated from iru, but the role(s) they play in the fermentation process has not yet been determined; this work thus seeks to determine if Staphylococcus spp. isolated from iru play any role in the fermentation of African locust bean. Bacillus spp. and Staphylococcus spp. isolated from spontaneously fermented African locust bean (iru) were used to ferment African locust beans. The temperature, pH and moisture content were determined as fermentation progress while the total soluble sugar and total free amino acid were determined after fermentation. The microbial load for the three iru products increased gradually until the end of fermentation. The total free amino acids increased in all three iru (1.10, 1.51 and 2.35 mg leucine ml-1 for Staphylococcus spp. iru, Bacillus spp. iru and iru produced with combination of the two species of bacteria) when compared with that of the unfermented bean, while the total soluble sugars reduced after fermentation with Staphylococcus spp. iru having 3.84, Bacillus spp. iru has 3.60, and the unfermented bean has 5.30 mg glucose ml-1 total soluble sugar. The increased free amino acids in the iru fermented with Staphylococcus spp. and the ability of the Staphylococcus spp. to produce lipase showed that Staphylococcus spp. isolated from iru has the ability to ferment African locust bean and carry out the lipolytic activity during the fermentation.

Keywords

• Staphylococcus spp.
• Bacillus spp.
• African locust bean
• Iru
• Fermentation