Microbiological changes in naturally fermented cassava fish (Pseudotolithus sp.) for lanhouin production

Cassava fish (Pseudotolithus sp.) was naturally fermented on three different occasions at room temperature (28-30 °C) for 3 to 8 days and the microbial population and the occurrence of various bacterial species were monitored. In general, after a slight increase during the early stages of fermentation, the microbial population decreased as the fermentation progressed. A total of 224 isolates belonging to the genera Bacillus, Staphylococcus, Micrococcus, Streptococcus, Corynebacterim, Pseudomonas, Achromobacter and Alcaligenes were isolated from the fermenting fish samples and the predominant ones were identified at the species level. Bacillus spp. and Staphylococcus spp. were the predominant genera and accounted for 48.7% and 27.3% of the total number of isolates respectively. Bacillus subtilis and Bacillus licheniformis, Staphylococcus lentus and Staphylococcus xylosus and Micrococcus luteus were the representative strains isolated during the fermentation. Bacillus spp., Staphylococcus spp. and Micrococcus spp. initiated the fermentation but Micrococcus spp. were few in numbers and died off after four (4) days of fermentation while Bacillus spp. and Staphylococcus spp. persisted up to the end of fermentation. Enterobacteriaceae were fewer in numbers at the start of fermentation (102 cfu/g) and their numbers decreased to less than 10 cfu/g after two days of fermentation. Bacillus spp. as well as Staphylococcus spp. isolated possessed moderate proteolytic and lipolytic activities. Micrococcus spp. showed weak proteolytic activity and no lipolytic activity.