The Microbial Activities Involved In The Alkaline Fermentation Of Soybeans Into Dawadawa

ABSTRACT

This study was initiated to identify the dominant microbial species and investigate their activities during the fermentation of soybeans to daw adaw a. The dominant microorganism s present in both the boiled and roasted soydaw adaw a, which were spontaneously fermented for 72 h, were isolated, characterized and identified using an API kit. The proteinase and a -a m y lase activities o f the microorganism s were determined. Q quality indices such as pH, m oisture, protein and fat contents of the soydaw draw a were measured. The breakdown of proteins during ferm entation o f soydaw adaw a w as studied using Gel electrophoresis. The trend in the level o f sugars during ferm entation o f soydaw adaw a w as carried out using the Lane and E ynon’s method. A rom atic com pounds (GC-M S m ethod) produced by the different types o f soydaw adaw a w ere also determ ined. Results show ed that Bacillus species w ere the dom inant m icro-organism s found and w hich increased from 10'’ to 10n cfu/g and 103 to 109 for the boiled and roasted soydaw adaw a from the start to the end o f ferm entation respectively. Lactic acid bacteria ( 104 to 106 cfu/g) w ere also found. Bacillus supplies accounted for 48% o f the representative isolates taken from various stages o f fermentation. Other Bacillus species accounted for 8% to 16% o f the isolates. All the identified Bacillus species demonstrated proteolytic activity in the order Bacillus subtilis >Baciflus furmis > Bacillus cerm s > Bacillus pumilus. At a = 0.05, proteolytic activity w as significantly affected by fermentation time and production method. H ow ever, there was no interaction betw een these tw o factors. a-am y lase activity w as positively affected by ferm entation tim e, increasing with increase in ferm entation time. H ydrolysis o f proteins during ferm entation w as confirm ed in^soydaw adaw a bv an increase in the fraction o f low er m olecular weight proteins and m ore distinct bands. The level o f sugars increased in the first 24 hours but decreased subsequently as ferm entation progressed. A rom a com pounds produced w ere m ore in the roasted products than the boiled. Both products w ere dom inated by 3-H exanol and 9, 12-O ctadecanoic acid. H ow ever, Tetradecanoic acid and 1,2-Benzene dicarboxylic acid w ere found only in the roasted product.