Microbial succession and biochemical changes associated with the production of sorghum "ogi":- Ofoegbu, Chidimma A

ABSTRACT

This study was to determine the microbiological and biochemical changes that occurs during fermentation of sorghum using Saccharomyces cerevisiae. 100g of sorghum grains were washed and placed in a clean bowl containing 2 litres of distilled water separately and then grinded. The grinded mash was allowed to ferment for 72 hours at room temperature 30 ± 2°C and analyzed at 24 hourly. Saccharomyces cerevisiae was isolated from Sorghum fermentation and sub-cultured on Yeast extract dextrose peptone (YEPD) agar at 30°C for 48 h and then by successive sub-culturing on YEPD broth at 30°C for 24 h and 18 h, respectively. Yeast strains were harvested by centrifugation at 4000 x g for 20 min and pellets was added in 50 ml of sterile sorghum worts and then incubated at 30°C for 24 h in order to initiate fermentation. Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Staphylococcus aureus, Lactobacillus casei and Lactobacillus brevis were the identified bacterial isolates while Aspergillusflavus, Aspergillums niger and Saccharomyces cerevisiae respectively were the fungal isolate. The heterotrophic bacterial plate count ranged from 3.5 to 7.6 x 10? cfu/g, coliform plate count ranged from 1.2 to 8.3 x 107cfo/g, while Lactic Acid Bacteria plate count ranged from 6.0 to 10.1 x 107cfu/g and Staphylococcus plate count ranged from 1.4 to 2.9 x 107cfu/g. The fungal plate count ranged from 1.5 to 8.3 x 107cfu/g and Yeast mean average plate count ranged from 5.3 to 8.9 x 107cfu/g respectively. The predominant microbial isolate were Lactobacillus brevis and Lactobacillus casei with total number of 5 (16.1%) each while Pseudomonas aeruginosa recorded the least microbial isolate of 1 (3.1%). The pH decreased with increase in fermentation time, and it ranged from 4.8 to 3.8 and Total titratable acidity increased within the 24-72 hours, followed by a gradual decrease. The least acidity was observed in all the unfermented.