This study was designed to purify and characterize of α-amylase from pure strain of Bacillus subtilis. The crude α-amylase was purified by ammonium sulphate precipitation, then loaded on DEAE Sephadex A-50 ion exchange chromatography and gel filtration. The effect of pH, temperature and metal ions were investigated on the purified enzyme. The single protein band on SDS-PAGE suggested that the enzyme was homogenous. Two different activity peaks were observed in ion exchange chromatography designated pool A and pool B with the 8% and 4% yield, 15.93 and 6.44 purification fold and specific activity 2.55 μmol/min/mg and 1.03 μmol/min/mg respectively. The two fractions revealed the same optimum pH 7.0 for the α-amylase activity while the enzyme was relatively stable at pH 4.0 and 7.0 between 20 to 40 minutes and 60 to 80 minutes for pool A and pH 8.0 between 40 and 100 minutes for pool B. At 40°C, optimum temperature was reached, and amylase activity was maintained at 75% and 70% temperature stability between 60 to 80 minutes for pool A and B, less than 20%, the residual activity at 60°C and 70°C was recorded. The incubation of α-amylase with Na + and Zn 2+ ions enhanced/activate the enzyme activity correspondingly, Al 3+ and K + ions exhibited varied degree of inhibition while Ca 2+ and Hg 2+ ions caused total inhibition on α-amylase activity. The ability of purified α-amylase from Bacillus subtilis under wide range of temperatures and pH suggests its applications in industries and bioremediation of effluent discharge on food processing sites.
The aim of this study was to isolate pectinolytic bacteria from fermented banana and orange peels. The bacterial isolates were identified using standard biochemical method. The bacteria isolates were screened on pectin agar plates. All the isolates showed pectinolytic activity in terms of making zone surrounding their colony on pectin agar medium. Pectinase activity was determined by dinitrosalicylic (DNS) acid method while protein concentration in the fermentation broth was quantified by Lowry method. The screened isolate designated OP6 tentatively identified as Leuconostoc mesenteroides with highest pectinase activity was subjected to mutagen (Ethidium bromide). The mutants of Leuconostoc mesenteroides generated were screened for pectinase production in comparison with the parent (wild) type in submerged state fermentation. All the mutant strains generated from Leuconostoc mesenteroides had their pectinolytic activities repressed in comparison with the wild strain. Out of mutants screened, mutant designated AB4 have the highest pectinolytic activity 1.54 U/mg. The pectinase activity produced by AB4 was approximately 32% lower than the wild strain. The pretreatment of Leuconostoc mesenteroides with Ethidium bromide caused enzyme repression. The appreciable yield in pectinase activity displayed by the mutant strains when compared with the wild type suggests its industrial relevance. Therefore, use of other chemical mutagens can be tested for further strains improvement.
This study was design to develop starter culture from lactic acid bacteria for improved nutritive value of linamarase treated cassava peels. Isolation and identification of bacteria were carried out using standard microbiological and biochemical methods. The grated cassava peels was pre-treated by subjecting to pasteurization process. Pasteurized samples were inoculated with prepared bacterial inoculum and incubated at 37°C for 24 hours in a sealed vessel. The samples were withdrawn at interval for viable cell count. The proximate evaluation, mineral and anti-nutrient contents of the fermented and inoculated-fermented samples were determined using standard methods. From the fermented and inoculated-fermented cassava peels, the microbial loads increased from 1.5 x 106 to 26.1 x 106cfu/ml and 1.0 x 106 to 6.3 x 106cfu/ml. The protein content showed a significant increase from 5.99 to 6.15% and 6.17 to 8.03% while crude fiber decreased from 14.33 to 13.01% and 14.46 to 11.47% respectively in fermented and inoculated-fermented samples. The cyanide content of the naturally fermented cassava peels decreased from 14.07 to 3.06 mg/kg while the inoculated-fermented cassava peels with linamarase-producing isolate showed a significant decrease in the cyanide content from 1.61 to 0.02 mg/kg respectively. Improvement in the nutritional composition with reduction in the anti-nutrient content of fermented and inoculated-fermented cassava peels suggest a promising and the application of these bacteria as biological tools in the production starter for the formulation of animal feeds.
Aim: This research investigated the antibacterial activities of the predominant microorganisms isolated from fermenting cassava mash during fufu production against selected enteropathogenic bacteria. Methodology: Microbiological analysis was carried out on the mash on daily basis during the three-day fermentation period. The pH, TTA and temperature of the fufu were also evaluated. The antibacterial activities of dominant microorganisms from the mash were assayed against the isolated microorganisms and test isolates using disc and agar diffusion methods. Results: The bacteria isolated from the fermenting mash include Bacillus subtilis, Lactobacillus fermentum, L. plantarum, Pediococcus acidilactici, Micrococcus luteus and Staphylococcus aureus while the fungi were Aspergillus flavus, A. niger, A. fumigatus, Geotrichum candidum, Penicillium expansum and Rhizospus stolonifer. The predominant microorganisms were L. plantarum, L. mesenteroides, A. niger, A. fumigatus and G. candidum. The total bacterial, lactic acid bacterial and fungal counts increased from 2.5X105 cfu/ml, 2.0X105 cfu/ml and 1.5X103 cfu/ml to 7.6X106 cfu/ml, 6.7X106 cfu/ml and 1.0X106 cfu/ml respectively. The temperature of cassava mash increased from 26°C to 30°C. The pH decreased from 6.80 to 4.22 while the total titratable acidity increased from 0.70% to 0.94%. Escherichia coli, P. mirabilis, S. typhimurium and S. aureus were inhibited by L. plantarum and L. mesenteroides while E. agglomerans and K. pneumoniae were resistant to L. plantarum and L. mesenteroides respectively. Aspergillus niger and G. candidum inhibited S. aureus but E. agglomerans, K. pneumoniae, P. mirabilis and S. typhimurium were not affected. Enterobacter agglomerans, E. coli, P. mirabilis and S. aureus were inhibited by A. fumigatus while K. pneumoniae and S. typhimurium were resistant. Conclusion: These results suggested that consumption of fufu and other fermented cassava tubers could enhance less susceptibility to diseases caused by the test bacteria and fufu may be recommended for people suffering from infections caused by these microorganisms.
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