A study of the optimal conditions for glucoamylases obtained from Aspergillus niger using amylopectin from cassava starch as carbon source

A fourteen day pilot study carried out showed that high glucoamylase activities were obtained on the 4 and 11th day of fermentation and the enzymes were harvested on the respective days giving the codes GluAgCSV4 and GluAgCSV11. The optimal pH and optimal temperatures for enzyme activities GluAgCSV4 and GluAgCSV11 were in a range of 6 to 7 and 50 to 55, using cassava, guinea corn and tiger nut starch as substrates, respectively. The enzyme activity (GluAgCSV4) was enhanced by Ca2+, Mn2+, Fe2+ and Zn2+. Co2+ had inhibitory effect on the enzyme while Pb2+ completely inactivated the enzyme. The enzyme activity (GluAgCSV11) was enhanced by Ca2+ and Co2+. Zn2+, Fe2+ Mn2+ and Pb2+ completely inactivated the enzyme. The Michaelis constant KM and maximum velocity Vmax obtained form Lineweaver-Burk plot of initial velocity data at different substrate concentrations were found to be 90.06 mg/ml and 188.67 μmol/min (using cassava starch as substrate), 173.70 mg/ml and 434.78 μmol/min (using guinea corn starch as substrate) and 28.57 mg/ml and 227.27 μmol/min (using tiger nut starch as substrate), respectively for GluAgCSV4. Also, 271.30 mg/ml and 1000 μmol/min (using cassava starch as substrate, 3093 mg/ml and 10000 μmol/min (using guinea corn starch as substrate) 2625 mg/ml and 10000 μmol/min (using tiger nut starch as substrate), respectively, were obtained for GluAgCSV4.Keywords: Glucoamylases, Aspergillus niger, amylopectin and starch

Effect of pH, various divalent metal ion and different substrates on glucoamylase activity obtained from Aspergillus niger using amylopectin from tiger nut starch as carbon source

Glucoamylases were obtained from Aspergillus niger using amylopectin from tiger nut starch as carbon source on the 5th (GluAgTN5) and 12th day (GluAgTN12) of fermentation. The optimal pH for GluAgTN5 at 55°C were 6.5, 7.0, 6.0 while that for GluAgTN12 were 8.5, 6.0, 7.5 at 50°C using cassava, guinea corn and tiger nut starch as substrates, respectively. The enzyme activity in GluAgTN5 was enhanced by Ca2+ and Fe2+ while Zn2+ and Co2+ had  inhibitory effects on the enzyme activity. Mn2+and Pb2+, however completely inactivated the enzyme. Enzyme activity in GluAgTN12 was enhanced by Ca2+ while Co2+and Zn2+ had inhibitory effects, Fe2+, Mn2+ and Pb2+ completely inactivated the enzyme. The Michealis-Menten constant, Km and maximum velocity, Vmax obtained from Line-Weaver-Burk plot of initial velocity data at different substrate concentrations were 222 mg/ml and 500 μmol/min, 291 mg/ml and 1000 μmol/min, 137.5 mg/ml and 500 μmol/min using cassava, guinea corn and tiger nut starch as substrate, respectively for GluAgTN5. While that for GluAgTN12 were 176.6 mg/ml and 100 μmol/min, 491 mg/ml and 1000 μmol/min, 131.5 mg/ml and 500 μmol/min using cassava, guinea corn and tiger nut starch as substrate, respectively.Key words: Glucoamylase, pH, metal ions, Aspergillus niger, tiger nut starch, amylopectin

Lipase activity in some Cucubitaceae species

Lipase activity was demonstrated in the endosperm of three varieties of both germinated and ungerminated seeds of Cucubitaceae: white melon (Cucumeropsis manii naud); yellow melon (Colocynthis vulgaris); pumpkin (Cucurbita moschata). Fractionation of homogenates by centrifugation yields that fat layer (lipid bodies), supernatant (water soluble fraction), and particulate fraction (pellets) with lipase located in all the fractions. The highest activity was determined in the lipid body fraction. However, a mixture of the lipid bodies and supernatant gave a much higher activity than the lipid body alone. Preparation of the supernatant at different pH's (4.0–9.0) and treating the supernatant with different concentrations of (NH4) 2SO4, further separated the lipid bodies with separation increasing as pH increases from 6.0 – 9.0. Separation of lipid bodies did not occur below pH 4 no enzyme activity was detected in the supernatant after precipitation with 90% (NH4) 2SO4. Lipase was tightly bound to the lipid body membranes as it resisted solubilisation by repeated washing with buffers and NaCl solutions. Ultrasonication of the lipid bodies and treatment with diethyl-ether extracted triacylglycerols from the lipid bodies with lipase activity being recovered in the membrane fractions. Bio-Research Vol. 3(1) 2005: 66-7

Physicochemical properties of lignocellulosic biofibres from South Eastern Nigeria: Their suitability for biocomposite technology

Five plant raw materials collected from South Eastern part of Nigeria were used for biofibre extraction and analysis to assess their suitability for biocomposite production. Lignocellulosic biofibres were extracted from young stems of Adenia lobata, Ampelocissus leonensis, Cissus palmatifida, Morinda morindoides and Urena lobata through natural water retting process for a period of 14 - 16 days and the resulting fibres were uniform with almost flat or circular cross sections. Phytochemical contents and extractives were determined on the untreated and treated fibres respectively. The %w/w cellulose contents of the pretreated biofibres were found to be 48.97± 1.33% for A. leonensis and 43.22±0.95% for A. lobata. The cellulose content of M. morindoides and C. palmitifida were found to be 55.76±1.40% and 55.20±1.59%, respectively. In all the plants studied, U. lobata had the greatest %w/w cellulose content of 58.94±1.05% while A. lobata had the least cellulose content of 43.22±0.95%. Estimation of %w/w hemicellulose contents showed A. leonensis to be 21.22±0.89% whilst the hemicelluloses content in A. lobata and U. lobata were observed to be 18.22±2.18% and 12.38±0.33% in that order. Lower hemicelluloses contents were obtained in C. palmitifida and M. morindoides as 10.32±1.27, 9.32±0.58 and 8.62±1.67%, respectively. The klason lignin contents were found to be 31.33±1.05% for C. palmitifida, 31.22±0.97% for M. morindoides, 28.22 ± 1.96% for A. lobata, and 24.91±0.61% for A. leonensis. The lignin content of U. lobata was found to be the least at 22.26±0.55%. Acid soluble lignin (ASL) content was greater in A. lobata (2.17±0.08%) while A. leonensis had the least value of 1.74±0.34%. ASL-derived products (vanillin, p-coumaric acid and ferulic acid) ranged between 0.50±0.12% and 1.41±0.02% for vanillin; 0.03± 0.02% and 0.65±0.14% for p-coumaric acid; and ferulic acid was only detected in A. leonensis as 0.41±0.11%. The mechanical properties of most fibres used in this study are comparable to those of other biofibres already used in manufacturing and can even match those of some synthetic fibres. Results obtained revealed that fibres used in this study had comparable properties with those already established for manufacturing in biofibre industries.Keywords: Biofibre, biocomposite, cellulose, lignin, hemicelluloses.African Journal of Biotechnology, Vol 13(20), 2050-205

Production and properties of fungal cellulase from native isolates using orange bagasse as carbon source

Orange bagasse was employed as the sole carbon source for production of cellulase having adapted the organisms on cellulose and on orange bagasse. The extracellular cellulase produced by Aspergillus niger and Rhizopus species were partially purified by ammonium sulphate precipitation in a single step and dialyzed. Cellulase activity of partially purified cellulase from Aspergillus niger and Rhizopus species were determined. Cellulase from both fungi had optimum temperature at 45°C but different pH optima of pH 7 and 6.5 respectively. Thermo stability study of the partially purified cellulases carried out over a temperature range of 35°C -70°C show that the enzymes lost stability with increasing temperature. Carboxymethylcellulase (CMCase) and Filter paper unit (FPU) activities of the partially purified cellulase show a higher specific activity for cellulase from Aspergillus niger than that from Rhizopus species.Key words: Cellulase, CMCase, Aspergillus niger, Orange bagass

Production and characterization of pectinases obtained from Aspergillus fumigatus in submerged fermentation system using pectin extracted from mango peels as carbon source

Pectinase was obtained from Aspergillus fumigatus in a submerged  fermentation system using pectin extracted mango peels as a carbon source and subjected to a two step purification system of 80% ammonium sulphate saturation and dialysis. Pectin was also extracted from mango peels and its extraction yield was found to be 17% at pH 2.2, temperature of 70¢ªC and extraction time of 1h. The protein concentration in the crude enzyme was found to be 1.372mg/ml. The specific activity of crude  enzyme is 11.20¥ìmole/min/mg. After 80% ammonium sulphate  precipitation and dialysis, the specific activities were 11.78¥ìmole/min/mg and 34.60¥ìmole/min/mg respectively. The maximal activity of A. fumigatus pectinase was at 40¢ªC, pH 5.5 and was heat stable up to 40¢ªC.Vmax and Km values were found to be of 625¥ìmole/min and 45.5mg/ml respectively. The pectinase was used to degrade pectins extracted from orange and pineapple peels and its specific activities were found to be 30U/mg and 28.39U/mg respectively as compared to 34.60U/mg which is the specific activity obtained when pectin extracted from dry mango peels was used.Key words: Mango peels, pectinase, pectin, Aspergillu fumigatus, submerged fermentation

Extraction, partial purification and characterization of pectinases isolated from Aspergillus species cultured on mango (Mangifera indica) peels

Pectinase was produced from a culture of Aspergillus niger, Aspergillus fumigatus and Aspergillus flavus. Pectinase synthesis was achieved using mango (Mangifera indica) pectin extract as an inducer during pectinolytic fungi isolation while submerged fermentation process was carried out using ground mango peels as the sole carbon source. Substrate fermentation was evaluated within seven days by monitoring the pectinase activity every 24 h. The highest pectinase secretion was obtained from A. niger and A. fumigatus after 92 h (day 4) of incubation, while in A. flavus, it was after 120 h (day 5). Crude enzyme extracts from the three organisms were partially purified by a combination of ammonium sulphate precipitation and dialysis with an approximately two-fold purification of the pectinase and a yield of 5.4, 7.66 and 5.99% for A. niger, A. fumigatus and A. flavus, respectively after dialysis. The specific activities of 1.62, 1.79 and 1.86 U/mg for A. niger, A. fumigatus and A. flavus enzymes were calculated, respectively. Pectinase from A. niger and A. fumigatus had pH and temperature optima of 5.0 and 40°C, respectively, while that from A. flavus had pH and temperature optima of 5.0 and 45°C. The Michealis constant, Km and the maximum velocity, Vmax determined from Lineweaver-Burk plots of initial velocity data at different concentrations of the mango pectin extract were 0.357 mg/ml and 35.34 U; 0.156 mg/ml and 68.0 U; and 0.261 mg/ml and 60.61 U; for the enzymes from A. niger, A. fumigatus and A. flavus, respectively. The results suggest that mango peels can be used for value added synthesis of pectinase, an important enzyme with numerous biotechnological applications.Keywords: Mango peels, mango pectin extract, pectinase, Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, submerged fermentation, partial purification, characterization.African Journal of Biotechnology, Vol 13(24) 2445-242

Production and Partial Characterization of Cellulases from Apergillus fumigatus Using Two Distinct Parts of Corn Cob as Carbon Sources

Corn cobs were sun-dried for three days and separated into the hard outer part (Corn Cob Outer, CCO) and the soft inner part (the pulp) (Corn Cob Inner, CCI). Each part was milled separately. Aspergillus fumigatus isolated from sewage water was grown on and adapted to each part of corn cob. Using CCI and CCO, as the sole carbon sources for submerged fermentation, the organism produced cellulase. Activity was highest on the 3rd and 4th days using CCI and CCO, respectively. The crude cellulases were partially purified by 50% ammonium sulphate precipitation followed by dialysis. The partially purified cellulases were then characterized with respect to pH, Temperature and Themostability. While the optimum pH of the CCI cellulose was 6.0, that of CCO cellulase was pH 7.0. The optimum temperature of CCI was 55°C whereas that of CCO was 50°C. The stability of enzymes from 35°C to 70°C was studied. At 70°C, CCO cellulase has lost 45.88% of its original activity while CCI cellulase lost 58.14%. The results show that corn cob could serve as a cheap carbon source for the production of fungi cellulase. The study indicates that waste could be converted to wealth.Key words: Corn cob, cellulose, Aspergillus fumigates, submerged fermentation, partial purification