Screening for a low-cost Haematococcus pluvialis medium reveals an unexpected impact of a low N:P ratio on vegetative growth

Haematococcus pluvialis is the current better source of natural astaxanthin, a high-value carotenoid. Traditionally, the production process of astaxanthin by this algae is achieved by a two-stage system: during the first stage, vegetative “green” cells are produced and then converted, in the second stage, into cysts that accumulate astaxanthin. In this work, a medium screening strategy based on the mixing of a 3-component hydroponic fertilizer was applied to identify a new formulation optimized for the vegetative stage. A maximal and high cell density of 2 x 106 cells mL−1 was obtained in a medium containing a high level of phosphate relative to nitrate, resulting in a N:P ratio much lower than commonly used media for H. pluvialis. In this medium, cells remained at the vegetative and motile stage during a prolonged period of time. Both high cell density culture and motile stage persistence was proved to be related to the N:P feature of this medium. We conclude that the macrozoid stage of H. pluvialis is favored under high-P and low-N supply and that low-cost hydroponic fertilizers can be successfully used for achieving high density cultures of vegetative cells of H. pluvialis.BIOVAMA

Net energy calculations for production of biodiesel and biogas from haematococcus pluvialis and nannochloropsis sp

Microalgae have been proposed as possible alternative feedstock for the production of biodiesel because of their high photosynthetic efficiency. However, the high energy input required for microalgal culture and oil extraction may negate this advantage. There is a need to determine whether microalgal biodiesel can deliver more energy than is required to produce it. Using the Cumulative Energy Demand method in Simapro®, net energy calculations were done on systems to produce biodiesel and biogas from two microalgae species: Haematococcus pluvialis and Nannochloropsis sp. In spite of very optimistic assumptions, the results show a large energy deficit for both systems. Largest contributions came from the energy required to culture the microalgae and the energy required to either dry the microalgae or to disrupt the cell wall. Recommendations are made to develop wet extraction and transesterification technology to make microalgal biodiesel systems viable from an energy standpoint. © Springer 2011