BIOETHANOL PRODUCTION FROM CORN COB USING CO-CULTURE OF ZYMOMONAS MOBILIS AND BACILLUS LICHENIFORMIS

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dc.contributor.authorMIGAP, HELEN HOOMSUK
dc.date.accessioned2024-09-24T13:41:38Z
dc.date.available2024-09-24T13:41:38Z
dc.date.issued2023-06
dc.descriptionA DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA NIGERIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF DOCTOR OF PHYLOSOPHY (PhD) IN MICROBIOLOGY DEPARTMENT OF MICROBIOLOGY, FACULTY OF LIFE SCIENCES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
dc.description.abstractThere have been growing interest about biosynthesis of fuels from renewable biomass resources due to depleting fossil resources and associated environmental issues in the past few decades. Bioethanol is considered to be a good choice for an alternative liquid fuel because it can be produced from a variety of agricultural renewable materials. Proximate analysis of corn cob was carried out and the results revealed that the substrate had the following nutritional composition: moisture (13.50%), ash (14.90%), crude protein (3.50%), lipid (1.00%) and carbohydrate (67.10%). The corn cob used in this research work had lipid and protein contents that can serve as sources of energy for microbial growth and replication. The substrate was rich in carbohydrates that have great potential for bio-ethanol production. In the present research work, Zymomonas mobilis an ethanologenic bacterium was isolated from palm sap and characterized molecularly by amplification of the alcohol dehydrogenase I gene and the 16SrRNA gene. A total of 10 Xylose fermenting Bacillus species were also isolated from the soil and characterized biochemically and through sequencing of the 16SrRNA genes. The sequences with their accession numbers have been deposited in the gene bank. The following Bacillus species were characterized: Bacillus amyloliquifaciens (20%), Bacillus licheniformis (20%), Bacillus thuringiensis (30%), Bacillus cereus (10%) and Bacillus subtilis (10%). Zymomonas mobilis isolates ZM2 and ZM3 were screened for alcohol tolerance and glucose fermentation to select the best to be used for bioethanol production. Growth of the two isolates were measured as optical densities at 540nm; Zymomonas mobilis isolate 3 (ZM3) had optical densities that ranged from 0.66-1.40 while ZM2 had optical densities that ranged from 0.34-1.36. ZM2 and ZM3 were also screened for glucose fermentation; ZM3 had ethanol yields that ranged from 30–80g/l while ZM2 had ethanol yields that ranged from 24-60g/l. ZM3 had higher optical densities in the presence of varying alcohol concentrations compared to ZM2 although it was not significantly different (P≥0.05). Similarly, ZM3 had higher ethanol yields compared to ZM2 which were significantly different (P≤0.05).The Bacillus isolates were screened for ethanol production from fermentation of xylose and cellulase production to select the best isolate for bioethanol production. The isolates had ethanol yields from the fermentation of xylose that ranged from 18.50-35.5g/l. Bacillus licheniformis (SCFB22) had the highest ethanol yield of 35.5g/l while Bacillus thuringiensis (SBX8) had the lowest ethanol yield of 18.50g/l. The cellulase activities of all the isolates ranged from 1.35-2.98FPU/ml. Bacillus licheniformis (SCFB22) also had the highest cellulase activity of 2.98FPU/ml while Bacillus thuringiensis (SBX3) had the lowest cellulase activity of 1.38FPU/ml. Acetic acid adaptation of Zymomonas mobilis isolate ZM3 was carried out by treating the isolate with varying amounts of acetic acid that ranged from 0.2-1.6 % to enhance the isolates‟ ability to withstand high concentrations of inhibitors like acetic acid during fermentation. Zymomonas mobilis isolate ZMA with a slightly enhanced tolerance to relatively high acetic acid concentrations was obtained. Submerged fermentation of corn cob hydrolysate was carried out using acetate adapted ZMA isolate, the parent Zymomonas mobilis isolate (ZM3) and xylose fermenting Bacillus licheniformis in set ups that contained co-culture of the two bacteria and those containing the single strains. High bioethanol yields of 38.6g/l and 35.3g/l were obtained from the coculture submerged fermentation of corn cob hydrolysate using acetate adapted Zymomonas mobilis (ZMA) and xylose fermenting Bacillus licheniformis (SCFB22) as well as co-culture submerged fermentation using the parent Zymomonas mobilis isolate (ZM3) and Bacillus licheniformis (SCFB22). Submerged fermentation using single isolates yielded relatively lower bioethanol contents. Isolates ZMA, Zymomonas mobilis ATCC 29191, ZM3, SCFB22 and Bacillus licheniformis ATCC 14580 had bioethanol yields of 32.1, 31.8, 31.9, 12.8 and 14.5g/l respectively. The acetate adapted isolate (ZMA) also had a higher ethanol yield of 32.1g/l than the parent isolate (ZM3) which had ethanol yield of 31.8g/ml. The results of the one way ANOVA that was carried out showed that the ethanol yields obtained from the coculture fermentation using different isolates were significantly different (P≤ 0.05). Co-culture fermentation using Zymomonas mobilis isolate ZMA, ZM3 and Bacillus licheniformis isolate SCFB22 have great potential for industrial bioethanol production using agricultural waste (corn cob). The physicochemical parameters of the bioethanol produced were all similar to that of the commercial 98% ethanol used in this study but with some variation in some of the parameters. All the bioethanol produced were colourless, the relative densities of the bioethanol produced ranged from 0.77-0.84g/cm3 while that of the commercial ethanol was 0.76 g/cm3.The variation in the relative densities of the bioethanol produced could be due to the different types of bacteria used in the set ups or the different bioethanol yields. The boiling points of the bioethanol produced were similar to that of the commercial ethanol. The boiling points of the bioethanol produced ranged from 78.6-78.9ºC while that of the commercial ethanol was 78.6ºC. The flash points of the bioethanol produced ranged from 14-16ºC while that of the commercial ethanol was 13ºC. The variation observed in the flash point of the bioethanol produced could be due to the fact that the bioethanol produced contained more water that the commercial ethanol. All the bioethanol produced as well as the commercial ethanol burned with a blue flame. The result of the physicochemical parameters of the bioethanol produced suggests that the bioethanol produced are of good quality and could serve as substitutes to conventional ethanol.
dc.identifier.urihttps://kubanni.abu.edu.ng/handle/123456789/13027
dc.language.isoen
dc.titleBIOETHANOL PRODUCTION FROM CORN COB USING CO-CULTURE OF ZYMOMONAS MOBILIS AND BACILLUS LICHENIFORMIS
dc.typeThesis
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