Determinants of astaxanthin industrial-scale production under stress caused by light photoperiod management of Haematococcus pluvialis cultivation

Abstract

Haematococcus pluvialis (Chlorophyta) is a microalga with the greatest capacity to generate pure natural astaxanthin with powerful antioxidant properties, through special cysts, in response to disruptions caused by stress conditions. This research tested the design of a prototype for applying artificial light photoperiods controlled by light-emitting diodes on an industrial scale for generating forced stress in H. pluvialis cells during two seasons of the year (winter and spring 2019) in the Coquimbo region in Chile. Three different culture structures were used for the four stages of the alga production cycle. Two containers, A and B, were used for the first and second culture stages, while a raceway (large pool) was used for the third and fourth culture stages. Experiments with four different photoperiods (PP) that represent hours of light:darkness were conducted in two trials (spring 16:8 and winter 18:6) and two for control (spring 11:13 and winter 10:14). In the experiment, an exponential increase of β-carotenoid was achieved, used in human and animal food for its health properties and as a natural colorant in the salmonids industry. Biomass and astaxanthin production under forced stress were measured with physical and chemical variables such as light intensity, temperature, pH, and dissolved oxygen. Results show that the spring culture showed a considerable increase of cysts and, therefore, of astaxanthin reservoirs, reaching a pigment production density of 276 g m-3, with the consequent increase in density of up to 22% more than the control PP.