Impact of physico-chemical parameters on the physiological growth of Arthrospira (Spirulina platensis) exogenous strain UTEXLB2340

Spirulina platensis is an attractive human food supplement, animals feed and of numerous medicinal uses. The effect of physico-chemical factors on the physiological growth rates as optical densities (O.D.) of S. platensis strain (UTEXLB2340) were investigated. Experiments were conducted at different pH levels, light intensities, and temperature regimes, and monitored for 20 days. The half concentration of Zarrouk media was found to be suitable for cultivation of this strain under indoor (1.14 O.D.) and outdoor conditions (0.99 O.D.). The nitrogen source sodium nitrate (2.5 gl-1) can be replaced by inexpensive and low concentration of urea fertilizer (0.12 gl-1). The growth rates of this strain were optimum at light intensities of 1500 to 2500 lux of continuous light (0.99 to 1.71 O.D.) or 2500 lux of intermittent light (1.32 O.D.). The optimal growth was recorded at lower pH 7 to 8 (1.19 to 1.76 O.D.), and temperature of 25 to 35°C (1.13 to 1.71 O.D.). Therefore, this microalga can be cultivated for commercial uses in the available natural ponds where the average temperature reached 30°C and light intensities fluctuated between 1000 to 4000 lux in the morning, 12,000 to 22,000 lux midday, and 7000 to 10,000 lux in the noon.Keywords: Arthrospira (Spirulina) platensis, indoor and outdoor cultures, light intensity, pH, sodium nitrate, temperature, urea.African Journal of Biotechnology Vol. 12(35), pp. 5458-546

Composition of Mycoflora and Aflatoxins in Lupine Seeds from the Sudan

Thirteen seed samples of lupines (Lupinus termis Forrsk.) were evaluated for their phytosanitary status by incubation on potato-dextrose agar (PDA) and moist sterile filter papers (blotter method) at 28±2ºC. The seeds were also assayed for the presence of aflatoxins and toxigenic fungi. Forty-seven species and 10 varieties in 14 genera of fungi were recovered. Among these, 45 species and 10 varieties were new to lupine seeds, and 5 species and 2 varieties were new to the mycoflora of the Sudan. The genus Aspergillus (10 species, 8 varieties) was the most common, followed by Rhizopus (1 species), Fusarium (6 species) and Alternaria (5 species), while the remaining genera (Chaetomium, Cladosporium, Curvularia, Drechslera, Penicillium, Phoma, Emericella, Mucor, Sclerotium, Ulocladium) displayed lower levels of contamination. Of possible pathogens on lupine plants, Alternaria (5 species) (stem lesion) and F. oxysporum (root rot) were recovered from the seeds. Thin-layer chromatographic analysis of chloroform extracts of the 13 seed samples revealed that two samples contained very low concentrations of aflatoxins B1 and B2 (4.5-6.5 µg/kg)