STUDIES ON GLUTAMIC ACID PRODUCTION BY BACILLUS ISOLATES INVOLVED IN 'DADDAWA' FERMENTATION

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Date
1988-11
Authors
OGBADU, JUMEYI LUCY
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Abstract
The fermentation of African locust bean (Parkia biglobosa) and soya bean (Glycine max) seeds for daddawa production are carried out by Bacillus species. The species which appeared to be responsible for the fermentation of locust bean seeds were found to be variable. In six separate fermentations, B._ subtilis, B. pumilus and B. licheniformis were identified. Bacillus subtilis predominated in four of the six fermentations. In soya bean fermentation, on the other hand, B._ subtilis and B._ pumilus were consistently isolated in all the three fermentations examined. The growth of the B._ subtilis was favoured by low oxygen tension. A rise in pH and temperature were observed in the fermentations of both African locust bean and soya bean. A comparative analysis of glutamic acid contents of both locust bean and soya bean daddawa showed higher value in the latter. Release and increase in glutamic acid in fermenting locust bean daddawa by B. subtilis- DU2 was observed to correspond with the trend of glutamic acid synthesis by the same isolate in a basal medium. A total of twenty-five Bacillus strains comprising of eight species were isolated from five Nigerian fermented vegetable proteins and fermenting daddawa. The Bacillus isolates were screened for glutamic acid producing ability in the basal medium. They were all found to produce glutamic acid in varying concentrations and are thus confirmed to contribute to levels of glutamic acid in the fermented vegetable proteins. Bacillus subtilis - DU2 involved in daddawa fermentation was selected for studies in which the effects of various nutrients and growth parameters on glutamic acid production were investigated. It was observed that glucose, sucrose, galactose and fructose, all of which are found in locust bean seeds supported high yields of glutamic acid. Some intermediates of the Kreb's cycle namely succinate and citrate supported yields of glutamic acid which were generally lower than those of the sugars. Biotin was essential for glutamic acid production and the optimal concentration was 4-6ug/l. Among the metal ions investigated, manganese and magnesium were the best while zinc was the least in supporting glutamic acid synthesis. Cobalt was found inhibitory to both growth and glutamic acid production of the isolate. The best pH and temperature range for optimum glutamic acid production were 7.5 and 3 5°C respectively. Urea, ammonium chloride and ammonium sulphate were found to support good glutamic acid production as nitrogen sources. When the basal medium was supplemented with different flours of leguminous seeds, there were no appreciable difference in the yield of glutamic acid over that of basal medium alone. Glutamic acid yield was highest in the soya bean supplemented medium followed by medium supplemented with locust bean, cowpea, peanuts and bambara nuts. The surface active agents, tween-80 and triton-X were incorporated into the media at the beginning and at 66th hour of the fermentation. Both surfactants caused increased glutamic acid yields by the organism and in about equal concentrations for optimal yields. Addition of the surfactants at the beginning of the fermentation had a more enhancing effect on glutamic acid release than their addition at 66th hour. Viability of the fermenting organisim did not appear to be affected at the concentrations of the surfactants used. Exposure of the wild B._ subtilis - DU2 to ultraviolet light and X-ray resulted in producing some strains which at 32°C produced levels of glutamic acid comparable with that of the wild strain but at 40°C, they (mutants) produced higher levels of the amino acid. There was no appreciable observable influence on the wild isolate exposed to acridine orange in glutamic acid synthesis.
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A DISSERTATION BY LUCY JUMEYI OGBADU SUBMITTED TO THE POST GRADUATE SCHOOL AHMADU BELLO UNIVERSITY, ZARIA. IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
Keywords
STUDIES, GLUTAMIC, PRODUCTION, BACILLUS, ISOLATES, INVOLVED, DADDAWA', FERMENTATION.
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