A new paradigm for producing astaxanthin from the unicellular green alga Haematococcus pluvialis

Abstract

The unicellular green alga Haematococcus pluvialis has been exploited as a cell factory to produce the high‐value antioxidant astaxanthin for over two decades, due to its superior ability to synthesize astaxanthin under adverse culture conditions. However, slow vegetative growth under favorable culture conditions and cell deterioration or death under stress conditions (e.g., high light, nitrogen starvation) has limited the astaxanthin production. In this study, a new paradigm that integrated heterotrophic cultivation, acclimation of heterotrophically grown cells to specific light/nutrient regimes, followed by induction of astaxanthin accumulation under photoautotrophic conditions was developed. First, the environmental conditions such as pH, carbon source, nitrogen regime, and light intensity, were optimized to induce astaxanthin accumulation in the dark‐grown cells. Although moderate astaxanthin content (e.g., 1% of dry weight) and astaxanthin productivity (2.5 mg L−1 day−1) were obtained under the optimized conditions, a considerable number of cells died off when subjected to stress for astaxanthin induction. To minimize the susceptibility of dark‐grown cells to light stress, the algal cells were acclimated, prior to light induction of astaxanthin biosynthesis, under moderate illumination in the presence of nitrogen. Introduction of this strategy significantly reduced the cell mortality rate under high‐light and resulted in increased cellular astaxanthin content and astaxanthin productivity. The productivity of astaxanthin was further improved to 10.5 mg L−1 day−1 by implementation of such a strategy in a bubbling column photobioreactor. Biochemical and physiological analyses suggested that rebuilding of photosynthetic apparatus including D1 protein and PsbO, and recovery of PSII activities, are essential for acclimation of dark‐grown cells under photo‐induction conditions. Biotechnol. Bioeng. 2016;113: 2088–2099. © 2016 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

Heterotrophy of filamentous oleaginous microalgae Tribonema minus for potential production of lipid and palmitoleic acid

“…2A, glycerol and sodium acetate had a slight but of no worth promotion on T. minus growth, and sucrose could barely offer any biomass accumulation, as well as xylose, galactose, mannose, L-rhamnose, maltose and starch investigated in this study but not shown here. Zhang et al (2016) reported that sodium acetate could be utilized as organic carbon source for Haematococcus pluvialis heterotrophy. Sucrose is another optional organic carbon substrate for microalgae heterotrophy, but it needs to be hydrolyzed prior to use (Wang et al, 2016c).…”

Astaxanthin extends lifespan via altered biogenesis of the mitochondrial respiratory chain complex III

“…Astaxanthin has been implicated in numerous health benefits in humans, including reduction in cardiovascular diseases, enhancement of the immune response and reduction in the occurrence of various cancers. (Ames 2018, Zhang and Wang 2015, Zhang et al . 2016).…”

Influence of inoculum size, CO2 concentration and LEDs on the growth of green microalgae Haematococcus pluvialis Flotow

“…This outcome revealed that the supply of CO 2 at 5% in basal medium stabilized the pH value throughout the culture period. As previously stated, pH was strongly dependent on the buffer capacity of the media [3,18,[22][23][24]. A lower concentration of CO 2 at 0.04% (air), 1% and 2.5% was insufficient, and the pH of the medium became more alkaline over time.…”