The growth of bacteria contaminants can be controlled in heterotrophic microalgae cultures by using an uncoupled supply of glucose and nitrate. However, till now this strategy was only described for fed-batch cultivation. The cultivation in a sequencing batch reactor (SBR) could be more promising for the industrial scale.
Biotechnologic processes based on microalgae cultivations have had an increasing interest from the early 2000s. Microalgae are microorganisms able to produce and accumulate a large variety of industrially relevant compounds starting from renewable and cheap resources. However, 3–10 € per kg of dry biomass is the minimum cost for microalgae biomass production that has been estimated by different studies published in 2016. This high cost restricts industrial applications only to the production of high-value products.
A fed-batch strategy is proposed to produce microalgae biomass under non-axenic heterotrophic conditions. The strategy induces the alternation of N-deplete (Glucose-replete) and N-replete (Glucose-deplete) cultivation phases by the periodic and uncoupled supply of glucose and NO3− to the culture. Cultivation of the microalga T. obliquus with this strategy reduced the ratio of the bacteria to microalgae cell concentration from 1.6, attained by conventional photoautotrophic cultivation, to 0.03.
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