Towards the development of a starter culture for gari production
Haakuria, Vetjaera Mekupi
Cassava is a food crop planted in many countries in Africa. Its tubers are a major source of food and are processed to produce a variety of food products, one of which is the fermented product called gari. This research report aimed to evaluate the performance of three lactic acid bacteria for several properties with regard to the fermentation of cassava to produce gari. Three organisms were used for the evaluation, namely Lactobacillus plantarum, Lactobacillus fermentum and Leuconostoc mesenteroides. The organisms were evaluated for viability, biomass formation and glucose utilisation in static flasks, biomass formation and glucose utilisation in 2 L fermenters, cell viability after dehydration processes and pH and cyanide reduction in cassava substrate. In static flasks, the organisms were found to retain above 80% cell viability after cryopreservation. Maximum biomass of 108 cells/ml was formed within the first 12 hours by all the organisms. While L. fermentum, depleted glucose within 24 hours, L. plantarum formed the highest biomass of 4 x 108 cells/ml. In 2 L Braunstat B fermenters, a cell count of 109 cells/ml was obtained by L. fermentum and Leuconostoc mesenteroides within 12-15 hours. Biomass formation for L. plantarum during the same period was 1010 cells/ml. Glucose was depleted within 12 - 15 hours. The viability of cells between the dehydration processes of centrifugation, glycerol and maltodextrin addition and lyophilisation, was above 80% for all the organisms. However, this high cell viability was influenced by concentration of cells during the centrifugation step. In cassava substrate, L. fermentum, though heterofermentative, was found to be particularly acid tolerant and reduced pH to 3.98. All the organisms were able to retain good viability after lyophilisation. However, the results of cyanide reduction were inconclusive. These results show that while cultures show promise for pilot scale studies of starter culture development, further cyanide experiments need to be conducted, and synergy between the organisms investigated.
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Homofermentative , Heterofermentative , Gari , Linamarase , Biomass production