The role of microorganisms in the fermentation of agbelima cassava dough

Abstract

The fermentation of cassava mash with a traditional innoculum into the widely consumed agbelima in Ghana, accomplishes four main objectives; a breakdown of the coarse texture, a souring of the dough, reduction in the content of cyanogenic glucosides and production of volatile aroma compounds. In all types of inocula examined, the breakdown of cassava texture occurs through the hydrolysis of cassava tuber cellulose by cellulases produced by some dominating microbial species in the inoculum. Bacillus subtilis and other Bacillus spp. including B. mycoides, B. pumilus, B. cereus, B. amyloliquefaciens and B. licheniformis are, the tissue degrading microbial agents in three types of inocula examined and the moulds, P. nodulum, P. citrinum and Geotrichum candidum in a forth type of inoculum whose biota is dominated by moulds.The souring of agbelima is accomplished through the production of lactic and acetic acids by Lactbacillus plantarum and other lactic acid bacteria including Lactobacillus brevis and Leuconostoc mesenteroides in all agbelima fermentations examined. Yeasts dominated by Candida krusei and also including Candida tropicalis and a Zygosaccharomyces spp. together with the above mentioned lactic acid bacteria are responsible for the production of volatile aroma compounds during agbelima fermentation. The major compounds produced are a non identified low molecular weight alcohol, 1-propanol, isoamylalcohol, ethylacetate, 3-methyl-1-butanol and acetoin. Substantial reductions occur in the levels of cyanogenic compounds present in cassava during agbelima fermentation and is enhanced through the use of traditional inoculum. The lactic acid bacteria and moulds isolated from agbelima all produce significant levels of the enzyme linamarase determined as β-glucosidase which is capable of breaking down the cyanogenic glucosides