Production of biomass and nutraceutical compounds by Spirulina platensis under different temperature and nitrogen regimes.
Blue green algae (spirulina) is a dietary system that is widely consumed as a whole food or as a supplement in many Asian countries where populations are mostly unaffected by many of the diseases currently afflicting western societies, such as cancer, heart disease and arthiritis. Indeed, spirulina is a rich source of antioxidants with the phenolic compounds playing a significant role. As components of a complex dietary system, phenolic compounds can act alone or through synergistic mechanisms to impart a greater biologic effect than can be elicited by a sum of the individual parts. Therefore, an understanding of the antioxidative mechanism(s) of spirulina's polyphenols can only be achieved by a thorough knowledge of their chemical profiles (types and quantities). As phenolic compounds are a richly diverse set of molecules, different extraction methods are therefore needed to thoroughly characterize the different types and amounts present in a whole system or complex matrix. As an initial first step in fulfilling this need, the objective of this project was to apply a response surface approach for obtaining highly potent antioxidative spirulina extracts in terms of their ability to scavenge free radicals and to correlate this health benefit to their phenolic content (total phenols / flavonoids). This objective was achieved by using six different extraction solvents, including methanol, ethanol, and acetone, with or without 1.2 N HCL and varying the solvent water ratio, mixing time, and solid / volume ratio. A three factor three-level face centered cube design was used for the response surface approach resulting in 16 samples per solvent system, which were prepared in triplicate. Each were then tested for total phenols, total flavonoids, and for their ability to scavenge a free radical. It was determined that optimal responses required different approaches. For example, the highest total phenols and flavonoids were obtained with acetone and methanol, respectively. Although acidified solvents were not needed for extracting the optimal TP and TF rich extracts, HCl was required for potent antioxidative extracts. In this case, ethanol + HCl produced the extracts with the highest antioxidative capacities. These results demonstrate that total amounts of TF and TP do not correlate to antioxidative capacities, and the effect is probably due to the different types of phenols and flavonoids present as well, which was evidenced by the compositional analysis of select extracts. This project is therefore significant in that critical information was obtained to characterize the extraction process …