Microbiology
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Item Fermentation conditions and process optimization of citric acid production by yeasts(Conscientia Beam, 2018) Afolabi, F. T.; Adeyemo, S. M.; Balogun, H. O.The aim of this study was to isolate and screen citric acid producing yeasts using low cost substrates. Thirty three yeast isolates were obtained from pineapple, plantain and sugar cane waste and identified as; Saccharomyces cerevisiae, Schizosaccharomyces pombe, Candida tropicalis, Pichia guilliiermondii, Debaromyces sp., Candida parapsilosis, Candida rugosa, and Candida krusei. Candida tropicalis had zone of clearance of 49±2.1 mm in diameter, Pichia guilliermondii had 40±1.2mm. Saccharomyces cerevisiae produced citric acid with glucose with 105.0 mg/l. C. tropicalis yielded 132.2 mg/l with sodium nitrate. S. cerevisiae and C. tropicalis produced citric acid at pH 6 with 23.70mg/l and 23.80mg/l. P. gulliermondii at pH 4 produced 23.00mg/l. The temperature of 30°C favoured S. cerevisiae and C. tropicalis yielding 40.80mg/l and 39.80 mg/l. After extraction, the yield of the citric acid was 4.231g, 3g of which was recrystallized to yield 2.16g of pure citric acid resulting into 72% recovery. The result indicated that pineapple wastes, plantain wastes and sugarcane cane are potential sources of yeasts that can be used for the production of citric acid.Item Isolation and characterization of ethanol-tolerant yeasts from decaying oranges for the production of bioethanol(Institute of Ecology and Environmental Studies, Faculty of Science, Obafemi Awolowo University (OAU), Ile-Ife, Osun State, Nigeria., 2017) Adeyemo, S. M.; Afolabi, F. T.; Awojobi, K. O.; Ojo, O. O.Decaying orange fruits are readily available agricultural waste in Nigeria, yet they seem to be underutilized as potential growth medium for local yeasts strains, despite their rich carbohydrate content that can support yeast growth. The ability of different strains of yeasts to grow on orange biomass and its utilization as raw material for the production of bio-ethanol was investigated in this study. Five replicate samples of decaying oranges were collected at different time intervals from dump sites at five different local markets in Ile-Ife from which different species of yeasts were isolated. Standard biochemical tests were conducted to identify and confirm their identities. Fermentation of orange juice was done with the yeast strains singly and in combination at 30°C for seven days and parameters essential for ethanol production such as titratable acidity, pH, specific gravity, Brix and Ethanol tolerance and content were determined following Association of Official Analytical Chemist procedures. Data were analysed using ANOVA at p=0.05. A total of thirty yeast isolates were isolated and identified as Saccharomyces cerevisiae, Schizosaccharomyces japanicus, Candida valida, Candida fructus, Candida krusei, Kluyveromyces africanus and Rhodotorula gramis. Abundant production of bioethanol was derived from S. cerevisiae, C. fructus and C. valida (C. fructus and C. valida were used singly while C. fructus and Saccharomyces were combined in the ratio 1:1). The highest alcohol value (7.65%) was derived from the mixed strain (Candida fructus and Saccharomyces cerevisiae) and the lowest value of alcohol (6.98%) from a single culture of Candida fructus. Decaying oranges, its juice and its biomass could be used to produce bio-ethanol which is of a good quality. The method is effective and efficient with high yield eco-friendly ethanol. The fruit waste which provides readily available and cheap substrates for industrial use and at the same time solves the problem of environmental pollution that the decaying oranges cause if not disposed appropriately.Item Bioethanol production from decaying oranges and pineapple juice using ethanol tolerant-yeast(Sciencedomain International, 2023) Omoolorun, J. B.; Afolabi, F. T.; Olufemi, S. E.; Adeyemo, S. M.Scientists across the globe ought to harness ways of getting alternative sources of energy which will be renewable, sustainable, efficient, eco-friendly, and cost effective because of the global energy crises owing to the cost of production, transportation and distribution of fossil fuel products. In Nigeria, decaying fruits always constitute a major environmental pollution during the harvesting season. This study screened, selected the best starter, and produced bioethanol from the juice obtained from decaying oranges and pineapple through the process of fermentation and distillation. Samples were collected from different locations within Ile-Ife and transported aseptically to the Laboratory. Microbiological and physicochemical assessment of the isolated strains were on yeast maintenance media. The cell biomass, pH, temperature, brix level, titratable acidity, specific gravity and ethanol yield were monitored during fermentation from day zero to day fourteen. Screening of the isolates obtained from a previous study was carried out to select the best starter for the production of bioethanol. S.cerevisae and K. marxianus and showed efficient physico-chemical attributes from the screening of the yeast isolates; a temperature of 30oC and pH 6 was the optimum for the growth of isolates tolerating 20% v/v absolute ethanol. Cultures were inoculated singly and in combination, S. cerevisiae gave the highest reduction in brix level from 2.2o at the onset and it reduced to 0.3o at the 21st day of fermentation while the least reduction was seen in K. marxianus. Mixed culture of S. cerevisiae and K. marxianus gave the highest reduction in brix level from 2.0o at the onset to 0.1o, pH reduced from 4.7- 3.3 while the cell biomass increased, and the temperature increased from 30oC to 34.5oC at the end of fermentation. Titratable acidity in the fermenting fruits juice increased from 0.23 to 1.76, the specific gravity reduced while the alcohol content increased from zero to 25.63 as the fermentation progressed and a reduction on day 21 (1.67) was observed. The use of decaying plant biomass or fruit waste can be a rich and cheaper source of substrate for different yeasts strains endogenous to the biomass for the production of environmental-friendly biofuel. This can also be employed as a waste management option and an alternative solution to environmental pollution and the global energy crises.Item Selection of starter from decaying oranges and pineapple for bioethanol production(Sciencedomain International, 2023) Omoolorun, J. B.; Afolabi, F. T.; Olufemi, S. E.; Adeyemo, S. M.Screening of yeasts for bioethanol production is an important aspect of industrial microbiology and biotechnology. Optimal yeast nutrition also requires availability of nutrients allowing for growth and ethanol production and ability to withstand the increasing concentration of the medium during fermentation. This study seeks to use appropriate methods to isolate, characterize and identify yeasts isolates with essential attributes for bioethanol production. Microbiological and Physicochemical assessment of the isolated strains was carried out on yeast maintenance media for the determination of ethanol, temperature and salt tolerance ability, growth at different pH and temperature, chloramphenicol and nalidixic acid test, determination of killer toxins production capacity of yeast, nitrate and carbon assimilation and sugar fermentation tests were carried out to select the best starter for production. Fifteen yeasts were isolated belonging to the genera Saccharomyces, Candida, Rhodotorula, Kluvyreomyces, Trichosporon, Pichia. S. cerevisae and K. marxianus showed efficient physico chemical attributes. Proximate analysis of fruits juice showed a moisture content between 81.83 – 86.37%, crude protein 1.33 – 2.00%, Ash 0.73 – 0.83%, carbohydrate 11.87 – 15.67% and Ether 0.1 – 0.5%. The total sugar ranged from 1.83 – 13.17, equal mixture of oranges and pineapple juice showed a sugar content of 15 which reduced during fermentation while the alcohol content increased. Organisms were able to tolerate a percentage of 4-30% ethanol content, tolerating 15% sodium chloride which is an index of osmotolerance. At higher concentration, growth reduced, organisms produced catalase, reduced nitrate and showed a variation in utilization of different sugars. At the end of the screening, S. cerevisiae and K. marxianus showed the best attribute essential for bioethanol production and were chosen as starters. The ability of the selected yeast isolates to produce Killer toxins against E. coli showed a negative result. Antibiotic sensitivity test was carried out on the selected yeast isolates using chloramphenicol and nalidixic and the two organisms were resistant to the antibiotics tested. The ability of the organisms to grow in changing environmental conditions and ethanol tolerance are attributes essential for production while Saccharomyces cerevisiae showed the highest attribute followed by Kluveromyces marxinus. This study concluded that Saccharomyces cerevisiae can be employed as starter in the industry for the production of bioethanol and in the conversion of agricultural waste to wealth.Item Isolation, production and optimisation of beta-galactosidase by utilizing yeasts isolated from selected dairy products(Tehran University of Medical Sciences, 2022) Afolabi, F. T.; Adewale, O. P.; Adeyemo, S. M.β-galactosidase is an enzyme that converts lactose into glucose and galactose. It alleviates the issue associated with intolerance to lactose and pollution caused as a result of milk by-products (whey). This study aimed to isolate and select yeast strains that can produce β-galactosidase from fresh milk, yoghurt and locally made cheese. A total of 115 yeasts were isolated from the samples, 9 yeast isolates had the ability to produce β-galactosidase and three (3) were selected for further analysis. β-galactosidase producers were screened using Ortho-nitrophenyl-β-D-galactopyranoside (ONPG) assay. Kluyveromyces marxianus strain SLDY–005 produced the highest β-galactosidase. It showed maximum enzyme activity (277 U/mL) at a temperature of 30oC, pH 5.5, after an incubation period of 36 h. Glucose decreased β-galactosidase production while yeast extract and urea were considered appropriate nitrogen sources for the best enzyme synthesis. Crude β galactosidase produced by Kluyveromyces marxianus SLDY – 005 was purified. The partially purified enzyme after dialysis showed a specific activity of 165.12 U/mL and had a purification fold of 6.02 and yield of 45.91 %. The purified enzyme had an optimum temperature of 40oC and a pH 6.0. Kluyveromyces marxianus strain isolated from local cheese is a potential candidate for the production of β-galactosidase and could be used to combat the problem of lactose intolerance.Item Fermentation conditions and process optimization of citric acid production by yeasts(Conscientia Beam, 2018) Afolabi, F. T.; Adeyemo, S. M.; Balogun, H. O.The aim of this study was to isolate and screen citric acid producing yeasts using low cost substrates. Thirty three yeast isolates were obtained from pineapple, plantain and sugar cane waste and identified as; Saccharomyces cerevisiae, Schizosaccharomyces pombe, Candida tropicalis, Pichia guilliiermondii, Debaromyces sp., Candida parapsilosis, Candida rugosa, and Candida krusei. Candida tropicalis had zone of clearance of 49±2.1 mm in diameter, Pichia guilliermondii had 40±1.2mm. Saccharomyces cerevisiae produced citric acid with glucose with 105.0 mg/l. C. tropicalis yielded 132.2 mg/l with sodium nitrate. S. cerevisiae and C. tropicalis produced citric acid at pH 6 with 23.70mg/l and 23.80mg/l. P. gulliermondii at pH 4 produced 23.00mg/l. The temperature of 30°C favoured S. cerevisiae and C. tropicalis yielding 40.80mg/l and 39.80 mg/l. After extraction, the yield of the citric acid was 4.231g, 3g of which was recrystallized to yield 2.16g of pure citric acid resulting into 72% recovery. The result indicated that pineapple wastes, plantain wastes and sugarcane cane are potential sources of yeasts that can be used for the production of citric acid.Item Isolation and characterization of ethanol-tolerant yeasts from decaying oranges for the production of bioethanol(Institute of Ecology and Environmental Studies, Faculty of Science, Obafemi Awolowo University (OAU), Ile-Ife, Osun State, Nigeria., 2017) Adeyemo, S. M.; Afolabi, F. T.; Awojobi, K. O.; Ojo, O. O.Decaying orange fruits are readily available agricultural waste in Nigeria, yet they seem to be underutilized as potential growth medium for local yeasts strains, despite their rich carbohydrate content that can support yeast growth. The ability of different strains of yeasts to grow on orange biomass and its utilization as raw material for the production of bio-ethanol was investigated in this study. Five replicate samples of decaying oranges were collected at different time intervals from dump sites at five different local markets in Ile-Ife from which different species of yeasts were isolated. Standard biochemical tests were conducted to identify and confirm their identities. Fermentation of orange juice was done with the yeast strains singly and in combination at 30°C for seven days and parameters essential for ethanol production such as titratable acidity, pH, specific gravity, Brix and Ethanol tolerance and content were determined following Association of Official Analytical Chemist procedures. Data were analysed using ANOVA at p=0.05. A total of thirty yeast isolates were isolated and identified as Saccharomyces cerevisiae, Schizosaccharomyces japanicus, Candida valida, Candida fructus, Candida krusei, Kluyveromyces africanus and Rhodotorula gramis. Abundant production of bioethanol was derived from S. cerevisiae, C. fructus and C. valida (C. fructus and C. valida were used singly while C. fructus and Saccharomyces were combined in the ratio 1:1). The highest alcohol value (7.65%) was derived from the mixed strain (Candida fructus and Saccharomyces cerevisiae) and the lowest value of alcohol (6.98%) from a single culture of Candida fructus. Decaying oranges, its juice and its biomass could be used to produce bio-ethanol which is of a good quality. The method is effective and efficient with high yield eco-friendly ethanol. The fruit waste which provides readily available and cheap substrates for industrial use and at the same time solves the problem of environmental pollution that the decaying oranges cause if not disposed appropriately.Item Probiotic effects of lactic acid bacteria and its use as bio-preservative for tomato juice and paste(New Century Health Publishers, LLC, 2017) Adeyemo, S. M.; Afolabi, F. T.; Awojobi, K. O.; Abiri, T. O.This research focused on the use of LAB isolated from fermented cereals as bio-preservative in extending the shelf life of Tomatoes. Twenty lactic acid bacteria were isolated from fermented cereal gruel ogi, were identified as L. plantarum, L. brevis, L. fermentum, L. bulgaricus and L. pentosus. L. plantarum showed increased production and activity of Lactic acid, Diacetyl and Hydrogen peroxide over a period of five days after which there was a significant reduction. Lactic cultures were used singly and in combination for bio-preservation after samples were pasteurized at 85°C for 15 min. LAB count increased significantly from 3.2x10 to 8.3x10 cfu/g during fermentation with lactic cultures monitored over a period of 7 days at room temperature. Total yeast, coliform and aerobic plate counts between days 3-5 were 2.5x10, 2.3x10 and 3x10 cfu/g, respectively. The LAB count decreased whereas others increased significantly between days 5-7. LAB demonstrated antagonistic activity against food borne pathogens suggesting it could be a good bio-preservative by contributing to enhanced shelf life and microbial safety of foods.Item Investigation on the microbial quality of raw meats sold in some parts of Ibadan metropolis, Nigeria(Valahia University Press, 2017) Afolabi, F. T.; Arowosebe, A. R.; Adeyemo, S. M.This study was carried out to assess the microbiological quality of fresh raw meats sold at butcher open shops in Ibadan metropolis, Oyo State, Nigeria. 16 samples of pork, goat, beef and chicken meats were obtained from 4 market locations and analyzed using standard microbiological techniques. The total viable count, total staphylococcal count, total enteric count, and total fungal count ranged from 1.0 x106 to 4.6 x 108, 5.0 x 104 to 1.0 x 107, 1.0 x 103 to 1.96 x 108, and 6.0 x 103 to 5.0 x 105 respectively. The percentage of microbial genera isolated from the meat samples were; Salmonella (7.45%), Shigella (6.21%), Staphylococcus (10.56), Micrococcus (17.39%), Enterococcus (1.24%), Streptococcus (4.35%), Yersinia (0.62%), Proteus (16.15%), Escherichia (7.45%), Paracolons (2.49%), yeast (9.94%), Klebsiella (5.59%), Enterobacter (1.86%), and Lactic acid bacteria (8.70%). 2.49% of the isolates obtained from goat meat showed heamolytic positive while 1.24%, 2.49%, and 0.62% of the isolates obtained from chicken, beef, and pig respectively, were able to lyse blood cells. This study confirmed the presence of probable pathogenic organisms in the raw meats sold in some parts of Ibadan metropolis. It significantly points to the great need to evaluate and monitor the occurrence rate of pathogenic organisms in livestock sold in Nigeria. There is also the need for proper and adequate cooking of food of animal origin prior consumption.Item Therapeutic effect of lactic acid bacteria isolated from freshly-harvested honey and its comb against food and wound- borne pathogens(New Century Health Publishers, LLC, 2016) Adeyemo, S. M.; Afolabi, F. T.; Ogunlusi, E. D.Honey has been extensively studied in the treatment of wounds but its efficacy in clinical practice is not fully understood. Lactic acid bacteria (LAB) have been used as bio-preservative in fermented foods. This work was carried out to evaluate the antagonistic effect of LAB present in fresh honey and its comb against some pathogens. LAB were isolated from five replicate samples of freshly harvested honey and its comb and identified as Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus plantarum and Lactobacillus lactis. Lactic acid, Diacetyl and Hydrogen peroxide (g/l) production were determined for 5 days. L. plantarum and L. brevis exhibited the highest and the lowest antimicrobials production, respectively. Agar well diffusion method was used to monitor the antagonistic activities against some pathogens. L. plantarum and L. brevis gave the highest zones of inhibition ranging from15 23mm on P. aeruginosa and S. aureus from food samples. They compete favourably with standard antibiotics set up as controls. Lactic acid bacteria demonstrated a significant antimicrobial activity; this shows its potential as probiotics in food preservation and its therapeutic effect in wound treatment. This also justifies the efforts directed by individuals in using honey to treat diabetic wounds.