Improving docosahexaenoic acid production by Schizochytrium sp. using a newly designed high‐oxygen‐supply bioreactor

Abstract

A sufficiently high oxygen supply is crucial for high‐cell‐density cultivation of aerobic microorganisms, including Schizochytrium sp. We, therefore, designed a novel bioreactor enabling high‐level oxygen supply, and its relevant process parameters and fermentation‐stage characteristics were investigated. The real‐time changes of pH and nonoil biomass were monitored as proxies for the consumption of nitrogen and lipid accumulation status, which was first applied to divided fermentation process with three stages. The experimental results showed that the biomass in this porous‐membrane‐impeller bioreactor was higher than in conventional bioreactor, while docosahexaenoic acid (DHA) percentage in total lipids was lower than in conventional bioreactor. A multistage control strategy is subsequently implemented for the porous‐membrane‐impeller bioreactor, and the maximum biomass, DHA concentration, DHA percentage in biomass and DHA productivity reached 151.0 g/L, 44.3 g/L, 29.33%, 369.08 mg/(L·h), respectively. This study thus provides a highly efficient and economic bioreactor for the production of DHA by Schizochytrium sp. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4278–4286, 2017

Repeated fed-batch strategy and metabolomic analysis to achieve high docosahexaenoic acid productivity in Crypthecodinium cohnii

“…The traditional source of DHA is fish oils. However, due to ocean pollution and sharp decrease of fish resources in recent decades, fermentation of heterotrophic microalgae has been proposed to be a promising alternative for DHA production [3,4]. Crypthecodinium cohnii, a DHA-rich heterotrophic marine microalgae, has received great interest since it contains more than 50% lipid content in its dry cell weight (DCW) [3,5]; and the ratio of DHA in total fatty acids (TFAs) approaches 50% [5]; furthermore, it does not contain any eicosapentaenoic acid (EPA) that is not suitable for infant use [6].…”

Resolving the formidable barrier of oxygen transferring rate (OTR) in ultrahigh-titer bioconversion/biocatalysis by a sealed-oxygen supply biotechnology (SOS)

“…However, unrestricted large-scale supply of pure oxygen not only leads to extremely low oxygen utilization, resulting in waste of resources and sharp increase in production costs, but also causes irreversible foam problem, which makes the timely updation of fresh gas difficult, and ultimately inhibiting microbial basal metabolism [20]. Moreover, several techniques have been employed in the bioreactor for strengthening OTR including elevated partial pressures of oxygen supplies [21], increased agitation rate [22], and modifying the vessel [23]. Additionally, it is feasible to add some oxygen carriers with high solubility to the broth.…”

The Dark Side of Microalgae Biotechnology: A Heterotrophic Biorefinery Platform Directed to ω-3 Rich Lipid Production

“…In any case, when producing microalgal lipids through heterotrophic metabolism, the cell oxygen requirements must be carefully considered, particularly during the microalgae active growth phase, being cell damage monitoring desirable, to avoid cell growth disturbance. Guo et al [33] developed a novel bioreactor design which enables a high oxygen supply, in combination with a DO-control strategy to improve the microalgal DHA production. A porous-membrane-blade impeller was used, leading to enhanced aeration and increased DO, which constitutes a novel bioreactor design.…”

“…Most of the recent works reporting lipid/DHA production from heterotrophic microalgae use traditional methods to monitor the microalgae growth during the culture development, such as optical density, dry cell weight and cell counting [19,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. However, these techniques provide no information on cell physiological states.…”