Vol 3, No 1

Table of Contents


Effect of Carbon Source of Growth on α-Amylase Production by a Strain of Penicillium funiculosum Thom. Isolated from Irish Potato (Solanum tuberosum Linn): Comparative Studies PDF
Adekunle Odunayo Adejuwon, Olusola Abiola Ladokun
Irish potato (Solanum tuberosum Linn.) is cultivated in the tropical middle belt of Nigeria. It is infested by a range of phytopathogens including Penicillium funiculosum Thom. In the present investigation, irish potato tubers and a defined growth medium were inoculated with pure culture of Penicillium funiculosum Thom. The composition of the defined medium was potassium dihydrogen sulphate, magnesium sulphate, calcium sulphate, hydrated iron sulphate, manganese sulphate, copper sulphate, zinc sulphate, thiamine, biotin, sodium nitrate as nitrogen source and varied carbon sources. Proteins which exhibited α-amylase activity were expressed and partially purified daily by ammonium sulphate fractionation followed by dialysis to remove small molecular weight impurities. The results showed that, optimum α-amylase activity was induced by the ninth day of inoculation of the potato tubers. Only traces of the α-amylase were observed in uninfected irish potato tubers. Similarly, starch, glucose, lactose, galactose, glucose and maltose as carbon source in the defined medium induced α-amylase activity varyingly. Highest value of induction was expressed when starch was carbon source followed by irish potato, then maltose glucose, sucrose, lactose, galactose consecutively. Earliest induction was with glucose with expression starting on the second day of inoculation of the defined growth medium. Inspite of being harmful to cultivation and storage of irish potatoes in Nigeria, West Africa, Penicillium funiculosum Thom. is a potential source of industrial production of α-amylase.

Expression of α-Amylase by Aspergillus flavus in Medium: Effect of Nitrogen Source of Growth PDF
Adekunle Odunayo Adejuwon, Anthonia Olufunke Oluduro, Femi Kayode Agboola, Patrick Ojo Olutiola
Aspergillus flavus is contaminant of storage products in the tropics. A defined medium with starch as carbon source and varied nitrogen sources was inoculated with spore suspensions of approximately 5x105 spores per ml of Aspergillus flavus. The nitrogen sources were ammonium chloride, urea, potassium nitrate, ammonium sulphate, glycine, sodium nitrate, tryptone and peptone. Extracellular α-amylase was produced by the fungus within a period of ten days in the inoculated defined medium. Peptone was able to induce highest α-amylase activity, expressed as 546 units/mg protein on the ninth day of inoculation of medium. Least activity were with tryptone and ammonium sulphate with optimum activities expressed as 5 units/mg protein on the eighth, ninth and tenth  days for tryptone and nil α-amylase activity on the tenth day when ammonium sulphate was nitrogen source.

The Effect of Carbon Source of Growth on α-Amylase Production by Aspergillus flavus PDF
Adekunle Odunayo Adejuwon, Patrick Ojo Olutiola
Background: Aspergillus flavus is known for its capability of production of aflatoxins in food grains in the tropics. It was also recently demonstrated as capable of production of α-amylase in a defined medium with potassium nitrate and some other nitrogen compounds as nitrogen source for fungal growth and development (Adejuwon et al., 2015, Advances in Bioscience and Bioengineering).  Materials and methods: In this current investigation a same defined growth medium with potassium nitrate as nitrogen source was inoculated with spore suspensions of approximately 7x105 spores per ml of Aspergillus flavus. The carbon source for growth was varied and was independently bread, starch, maltose, sucrose, lactose, glucose and galactose. Incubation was at 30oC. Extracellular proteins produced in medium was monitored daily and analysed for α-amylase activity. Results: The proteins produced by Aspergillus flavus in the inoculated medium exhibited α-amylase activity. All the carbon compounds used in the investigation supported α-amylase expression in the fungus however, starch and maltose were the most supportive with optimum activity expressed as 417 and 364 units/mg protein respectively on the 5th day of incubation. Slight delayed expressions were with bread, starch, maltose, lactose, glucose and galactose.  Conclusion: All the carbon compounds used in this investigation will support industrial production of α-amylase by Aspergillus flavus with starch and maltose being most supportive when potassium nitrate is used as a source of nitrogen for growth and development at 30oC. However, Aspergillus flavus poses a danger as a potential biomarker in bioterrorism.

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