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Spirulina platensis (SP) has a high impact on multidiscipline usage worldwide. Vitamins are considered as growth promoters due to their metabolic bio-regulating roles. This study was conducted to investigate the effect of vitamins: riboflavin (B2), thiamine (B1), and ascorbic acid (C) on SP growth and contents of pigments, phenols, and phytochemicals besides its antioxidant activities. Vitamins were added in different concentrations to Zarrouk’s medium and tested for their effects weekly for three weeks of spirulina cultivation. The results revealed that 25 mg·L−1 thiamine or riboflavin promoted the most significant contents of chlorophyll and carotenoids, respectively, after 14 days of cultivation. However, adding 10 mg·L−1 thiamine achieved the most significant increase in algal biomass yield and contents of chlorophyll, carotenoids phycocyanin, allophycocyanin, phycoerythrin, and phycobiliprotein after 21 days of cultivation. Qualitative analysis showed that both SP and SP supplemented with 10 mg·L−1 thiamine (SPt) for 21 days contain tannins and flavonoids but quantitative analysis approved that SPt recorded significant increase in phenolic and tannin contents. Moreover, SPt induced a significant increase of total antioxidant activity in vitro 1,1-diphenyl-1,2-picrylhydrazyl assay in comparison with SP. Vitamins especially thiamine added during SP culture could improve SP biomasses, pigments, and phytochemical contents and hence increased antioxidant capacity.

The enormous industrial usage of nickel during its manufacture and recycling has led to widespread environmental pollution. This study was designed to examine the ability of Gelidium amansii biomass to biosorb Ni2+ ions from an aqueous solution. Six independent variables, including contact time (1.0 and 3.0 h), pH (4 and 7), Ni2+ concentration (25 and 200 mg·L−1), temperature (25°C and 50°C), G. amansii biomass (1.0 and 4.0 g·L−1), and agitation mode (agitation or static), were investigated to detect the significance of each factor using a Plackett–Burman design. The analysis of variance for the Ni2+ biosorption percentage indicated that three independent variables (contact time, temperature, and agitation–static mode) exhibited a high level of significance in the Ni2+ biosorption process. Twenty experiments were conducted containing six axial, eight factorial, and six replicates points at center points. The resulting face-centered central composite design analysis data for the biosorption of Ni2+ exhibited a very large variation in the removal percentage of Ni2+, which ranged from 29.73 to 100.00%. The maximum Ni2+ biosorption percentage was achieved in the 16th run with an experimental percentage quantified as 100.00% under the experimental conditions of 3 h of incubation time and 45°C with 100 rpm for agitation speed.