Aims: Variation in the traditional growth medium conditions to enhance the production of lipids, carbohydrates, protein and the free amino acids content of three cyanobacterial species. Methodology and Results: Three species of cyanobacteria (Anabaena laxa, Anabaena fertilissima and Nostoc muscorum) were collected from the culture collection of Soils, Water and Environment Research Institute, Agriculture Research Center, Giza, Egypt, to investigate their biochemical composition under different growth conditions, using BG110 (nitrogen free) as growth medium. These conditions were represented by control medium, static glucose medium with (1%, w/v), aerated medium (aerated by bubbling technique depending on CO2 normally existed in air with a concentration of 0.03%), molasses medium (0.7%, v/v) and aerated medium enriched with glucose (1%, w/v). Lipid content, total carbohydrates, soluble proteins and free amino acids were determined at the previous conditions. Glucose at 0.7% (w/v) was the most favorable for lipid production in A. laxa, where it exhibited the highest lipid content (427 µg/g fresh wt.). Increasing molasses concentration up to 0.7% (v/v) produced an increase in lipid contents of the tested cyanobacterial strains. The highest lipid content of both N. muscorum (366.2 µg/g fresh wt.) and A. laxa (357.4 µg/g fresh wt.) were recorded at molasses concentrations of 0.1 and 0.7% (v/v), respectively. A. laxa expressed high significant values for both proteins (31.6 µg/mL) and free amino acids (40.5 mg/g dry wt.) after 6 days of incubation period under aerated enriched glucose condition (1%, w/v). Also, at the same growth conditions, A. fertilissima exhibited high significant values for carbohydrates at 4 th day (876.8 mg/g dry wt.). Conclusion, significance and impact of study: Aerated enriched glucose medium (1%, w/v) was the best growth medium condition used in the present study.

In this investigation, antimicrobial activity of Nostoc commune Vauch (isolated from agricultural wastewater canal, Beni Suef Governorate, Egypt) organic extracts were examined against nine selected microbial isolates. Four of them were Gram positive bacterial isolates (Bacillus subtilis, Mycobacterium phlei, Sarcina maxima and Staphylococcus aureus), four Gram negative bacteria (Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa and Salmonella arizonae) and one unicellular fungus (Candida albicans) were evaluated for their resistance against these extracts. Methanol was the best organic solvent for extraction of active material, rather than the other organic solvents. This material was produced, maximally, after 10 days of incubation in aerated shaken culture at 30ºC and pH 8.0 when N. commune was grown in Medium 18 growth medium. The antagonistic material was purified using thin layer chromatography then identified using chromatographic and spectroscopic techniques including UV, FT-IR, mass spectrophotometer and proton-NMR. Four unknown compounds were extracted that had long chain alcohol, sterol, long chain fatty acid and triterpen. These compounds were tested for their antimicrobial activity against B. subtilis. Only the long chain fatty acid (compound C) had an inhibitory effect on the growth of B. subtilis while the other compounds were not active.

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