Production and characterization of amylase by mixed cultures of Aspergilllus flavus and Aspergillus tamarii

This study evaluated the potentials of mixed cultures of Aspergillus flavus and A. tamarii used for enhanced amylase production. Amylase producing moulds were screened from the soil by plating on Remazol Brillant Blue-Starch agar. Out of the 800moulds screened, studies were conducted on amylase production of monocultures and mixed cultures of  non-aflatoxigenic Aspergillus flavus(A) and Aspergillus tamarii(C) by growing them on rice bran solid media at 30°C for 72h. The synergy between the two moulds was pronounced at 70°C and pH 6.0, 7.0 where the enzyme activity of the mixed culture(E) was 2.5 times higher than that of the monocultures. Storage stability with Cassava starch and Soyabean flour showed that the maximal enzyme stability of 95% was obtained with 3% (w/v) of Cassava starch at 4°C while 96% enzyme stability was  achieved with 4% (w/v) Soyabean flour at 30°C over a period of 8weeks. Thin Layer Chromatography of starch hydrolysates showed a mixture of glucose and maltose from extracts of A with only maltose from C  suggesting that A produced glucoamylase and á-amylase while C produced only α-amylase. This study shows that extracts of the mixed cultures contain enzyme complex that can be of high importance in the starch industry.Keywords: Microorganisms, amylase, pure Culture, mixed Culture

Prospects of Biocatalyst Purification Enroute Fermentation Processes

Biotransformation of broth through fermentation process suffers a major setback when it comes to disintegration of organic substrates by microbial agents for industrial applications. These biocatalysts are in crude/dilute form hence needs to be purified to remove colloidal particles and enzymatic impurities thus enhancing maximum activity. Several contractual procedures of concentrating dilute enzymes and proteins had been reported. Such inorganic materials include ammonium sulphate precipitation; salting, synthetic polyacrylic acid; carboxy-methyl cellulose, tannic acid, edible gum and some organic solvents as precipitants etc. The emergence of organic absorbents such as sodom apple (Calostropis procera) extract, activated charcoal and imarsil had resulted in making significant impact in industrial circle. Various concentrations of these organic extracts have been used as purifying agents on different types of enzyme vis: lipase, amylase, protease, cellulase etc. Purification fold and stability of the enzyme crude form attained unprecedented results

Production and characterization of amylase by mixed cultures of Aspergilllus flavus and Aspergillus tamari

This study evaluated the potentials of mixed cultures of Aspergilllus flavus and A. tamarii used for enhanced amylase production. Amylase producing moulds were screened from the soil by plating on Remazol Brillant Blue-Starch agar. Out of the 800moulds screened, studies were conducted on amylase production of monocultures and mixed cultures of non-aflatoxigenic Aspergillus flavus(A) and Aspergillus tamari (C) by growing them on rice bran solid media at 30\ub0C for 72h. The synergy between the two moulds was pronounced at 70\ub0C and pH 6.0, 7.0 where the enzyme activity of the mixed culture(E) was 2.5times higher than that of the monocultures. Storage stability with Cassava starch and Soyabean flour showed that the maximal enzyme stability of 95% was obtained with 3% (w/v) of Cassava starch at 4\ub0C while 96% enzyme stability was achieved with 4% (w/v) Soyabean flour at 30\ub0C over a period of 8weeks. Thin Layer Chromatography of starch hydrolysates showed a mixture of glucose and maltose from extracts of A with only maltose from C suggesting that A produced glucoamylase and \u3b1-amylase while C produced only \u3b1-amylase. This study shows that extracts of the mixed cultures contain enzyme complex that can be of high importance in the starch industry

Purification and characterization of thermostable glucoamylase from Rhizopus oligosporus SK5 mutant obtained through UV radiation and chemical mutagenesis

Thermostable glucoamylase from Rhizopus oligosporus SK5 mutant was purified in a 3-step purification using Imarsil, activated charcoal and Sephadex-G-100 to achieve a 40-fold purification. The enzyme was optimally active at pH 5.0 and temperature of 80 \ub0C. It exhibited a half-life of 60 minutes at 70 \ub0C. Its stability was enhanced with addition of Soyabean flour or starch (3% w/w) leading to a retention of over 90% residual activity at 4 \ub0C and 28 \ub0C after 12 weeks of storage. SDS-PAGE analysis of purified enzyme showed two major bands with corresponding molecular weights of 36 kDa and 50 kDa. The study presents thermostable glucoamylase from Rhizopus oligosporus SK5 as a potential in the bioconversion of starch to glucose

Removal of Mn(II) from aqueous solution by Irvingia gabonensis immobilized Aspergillus sp. TU-GM14: Isothermal, kinetics and thermodynamic studies

A BSTRACT Irvingia gabonensis immobilized Aspergillus sp. TU-GM14 was used for the removal of Mn 2+ from aqueous solution in batch system. Effect of biosorption variables such as pH, adsorbent dosage, contact time and initial metal ion concentration were investigated. Experimental data obtained from batch equilibrium studies were subjected to twoparameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and three-parameter (Redlich-Peterson (R-P), Sips, Koble-Corrigan and Toth) isotherm models. The experimental data were fitted to the isotherms with R 2 > 0.9. The biosorption energy (E) from the D-R isotherm was found to be 0.13 kJ/mol, which indicates physisorption favoured process. Kinetic data were analysed with n th -order, modified second-order, Avrami and Elovich kinetic models. Both n th and modified second-order kinetic models best fitted the data with coefficient of determination (R 2 ) above 0.999 along with average relative and hybrid errors lower than 5%. Intraparticle diffusion model analysis showed that the biosorption process occurs in two stages as rapid and slow phases. The calculated thermodynamics parameters (∆G o ,∆H o and ∆S o ) indicated that the process is spontaneous and endothermic in nature

Bioconversion of corn straw to ethanol by cellulolytic yeasts immobilized in Mucuna urens matrix

Production of bioethanol from corn straw by cellulolytic yeasts immobilized on Mucuna urens was investigated. Yeast isolates were screened for amylase, cellulase and ethanol production. Effect of bead size, inoculum load, substrate concentration, pH and bead reusability were studied. Bioethanol production was optimum with 4 mm bead size, 10% substrate concentration, pH 4.5 and 10% inoculum load. Maximum ethanol production (55.27 g/L) was achieved by immobilized Saccharomyces diaststicus. Immobilized yeast cells were re-used repeatedly without obvious loss of activity. This study showed that yeasts immobilized on Mucuna urens can effectively utilize lignocellulolytic materials and produce ethanol from it. Keywords: Bioethanol, Yeasts, Immobilization, Mucuna urens, Saccharomyces diastaticu

Extent of Microbial Contamination of Refined and Unrefined Vegetable oils sold in South-west Nigeria

Oils constitute a major source of plant-based protein. A major limitation to optimal oil consumption in sub-tropical region is fungal infestation and consequent mycotoxin contamination. Ten refined and eight unrefined vegetable oils were randomly purchase from open markets and screened for microbial contamination using standard microbial procedures. Twenty six fungi isolates were obtained from the vegetable oil samples, the isolates were identified as Aspergillus fumigatus (43.0%), Mucor (17.9%), Saccharomyces cerevisiae (10.7%), Aspergillus niger (7.1%), Aspergillus flavus (7.1%), Penicillium spp (7.1%), Aspergillus oryzae (3.6%), Mucor (17.9%) and Rhizopus spp (3.6%). Five out of the ten refined vegetable oil samples had no fungal contamination. A. flavus and A. oryzae were absent in all the refined oil samples while A. niger was absent in all the unrefined oil samples. Isolation of mycotoxigenic fungi such as Aspergillus spp. is of vital importance in the food industry. Education and training of processors and consumers is recommended