Efficient one‐step production of astaxanthin by the microalga Haematococcus pluvialis in continuous culture

Abstract

The performance of Haematococcus pluvialis in continuous photoautotrophic culture has been analyzed, especially from the viewpoint of astaxanthin production. To this end, chemostat cultures of Haematococcus pluvialis were carried out at constant light irradiance, 1,220 μE/m2 · s, and dilution rate, 0.9/d, but varying the nitrate concentration in the feed medium reaching the reactor, from 1.7 to 20.7 mM. Both growth and biomass composition were affected by the nitrate supply. With saturating nitrate, the biomass productivity was high, 1.2 g/L · d, but astaxanthin accumulation did not take place, the C/N ratio of the biomass being 5.7. Under moderate nitrate limitation, biomass productivity was decreased, as also did biomass concentration at steady state, whereas accumulation of astaxanthin developed and the C/N ratio of the biomass increased markedly. Astaxanthin accumulation took place in cells growing and dividing actively, and its extent was enhanced in response to the limitation in nitrate availability, with a recorded maximum for astaxanthin cellular level of 0.8% of dry biomass and of 5.6 mg/L · d for astaxanthin productivity. The viability of a significant continued generation of astaxanthin‐rich H. pluvialis cells becomes thus demonstrated, as also does the continuous culture option as an alternative to current procedures for the production of astaxanthin using this microalga. The intensive variable controlling the behavior of the system has been identified as the specific nitrate input, and a mathematical model developed that links growth rate with both irradiance and specific nitrate input. Moreover, a second model for astaxanthin accumulation, also as a function of irradiance and specific nitrate input, was derived. The latter model takes into account that accumulation of astaxanthin is only partially linked to growth, being besides inhibited by excess nitrate. Simulations performed fit experimental data and emphasize the contention that astaxanthin can be efficiently produced under continuous mode by adjustment of the specific nitrate input, predicting even higher values for astaxanthin productivity. The developed models represent a powerful tool for management of such an astaxanthin‐generating continuous process, and could allow the development of improved systems for the production of astaxanthin‐rich Haematococcus cells. © 2005 Wiley Periodicals, Inc.

Efficiency assessment of the one‐step production of astaxanthin by the microalga Haematococcus pluvialis

“…Analysis of variance confirmed that together with a large influence of the nitrate supply (Del Río et al, 2005), the irradiance could also have a marked enhancing effect on the accumulation of astaxanthin by Haematococcus cells in continuous culture. This behavior became also apparent by plotting the astaxanthin content of the biomass from 43 different cultures maintained under steady state conditions versus the specific nitrate input, the data being grouped in four separate series corresponding to different average irradiance ranges (Fig.…”

“…Besides representing an efficient and simple production process, the fact that the growing and dividing cell population exhibited active astaxanthin accumulation demonstrated that such ability neither required encystment nor was a property unique to non-growing cells, as assumed by others (Borowitzka et al, 1991;Boussiba, 2000;Boussiba et al, 1999;Fábregas et al, 2001;Harker et al, 1996;Kobayashi et al, 1997). A preliminary assessment of the one-step system yielded a considerably high productivity, of 5.6 mg astaxanthin/L day (Del Río et al, 2005). Notwithstanding, productivity and efficiency of the one-step system versus the two-stage counterpart have recently been challenged by Aflalo et al (2007), on the ground that 'there is no real biotechnological advantage to vigorously growing cells for production of the secondary carotenoid astaxanthin.…”

“…The term specific nitrate input, SNI (Del Río et al, 2005) refers to the amount of nitrate (mmol) made available to cells (g dry biomass) per time unit (day). It can be observed that the lower the SNI value, the higher the average irradiance needed to reach the same growth rate (Fig.…”

“…Notwithstanding, productivity and efficiency of the one-step system versus the two-stage counterpart have recently been challenged by Aflalo et al (2007), on the ground that 'there is no real biotechnological advantage to vigorously growing cells for production of the secondary carotenoid astaxanthin. ' The early performance analysis of the one-step system was limited to the effect of varying nitrogen supply to the cell suspension, keeping otherwise constant both the dilution rate and the illumination conditions (Del Río et al, 2005). This represents a limitation in the robustness and reach of conclusions and capacities of the system.…”

Evaluación físico-química de aceite pigmentado obtenido de la cabeza de camarón

“…Presenta un color rojo-anaranjado por lo que se utiliza para pigmentar el salmón, truchas, crustáceos y algunas aves. Además, posee mayor actividad antioxidante que la vitamina E, debido a esto se utiliza en productos nutracéuticos y cosméticos (Higuera-Ciapara et al, 2006;Del Río et al, 2005).…”