Optimizing Docosahexaenoic Acid (DHA) Production by Schizochytrium sp. Grown on Waste Glycerol

Natalia Kujawska,Marcin Dębowski,Szymon Talbierz,Joanna Kazimierowicz,Marcin Zieliński

doi:10.3390/en14061685

Natalia Kujawska, Marcin Dębowski + Show 3 more

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https://doi.org/10.3390/en14061685

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Abstract

The aim of this study was to optimize biomass and docosahexaenoic acid (DHA) production by Schizochytrium sp. grown on waste glycerol as an organic carbon source. Parameters having a significant effect on biomass and DHA yields were screened using the fractional Plackett–Burman design and the response surface methodology (RSM). Schizochytrium sp. growth was most significantly influenced by crude glycerin concentration in the growth medium (150 g/dm3), process temperature (27 °C), oxygen in the bioreactor (49.99% v/v), and the concentration of peptone as a source of nitrogen (9.99 g/dm3). The process parameter values identified as optimal for producing high DHA concentrations in the biomass were as follows: glycerin concentration 149.99 g/dm3, temperature 26 °C, oxygen concentration 30% (v/v), and peptone concentration 2.21 g/dm3. The dry cell weight (DCW) obtained under actual laboratory conditions was 66.69 ± 0.66 g/dm3, i.e., 1.27% lower than the predicted value. The DHA concentration obtained in the actual culture was at 17.25 ± 0.33 g/dm3, which was 3.03% lower than the predicted value. The results obtained suggest that a two-step culture system should be employed, with the first phase focused on high production of Schizochytrium sp. biomass, and the second focused on increasing DHA concentration in the cells.

Highlights

The properties of microalgae make them a useful resource for environmental engineering technologies, including wastewater treatment, bio-sequestration of carbon dioxide, manufacture of biofuels, and sorption of contaminants [1,2]
The present study showed that dry cell weight (DCW) and docosahexaenoic acid (DHA) levels in Schizochytrium sp. microalgae are most significantly influenced by: temperature, crude glycerin concentration in the medium, oxygen concentration, and peptone concentration in the bioreactor
The present study demonstrated that a crude glycerin concentration of 150 g/dm3 led to the highest DCW levels at 67.55 g/dm3, as well as an increase of DHA concentration in Schizochytrium sp. cells to 17.25 g/dm3

Summary

Introduction

The properties of microalgae make them a useful resource for environmental engineering technologies, including wastewater treatment, bio-sequestration of carbon dioxide, manufacture of biofuels, and sorption of contaminants [1,2]. Microalgal biomass is a source of value-added products useful in medicine, pharmaceuticals, fertilizer industry, animal feed industry, and the food sector [3,4]. One of the most promising and encouraging options is found in the development of technologies that use waste substrates as the main growth medium ingredient [7,8], a method consistent with the idea of the circular economy and the principles of an integrated biorefinery approach [9]. With the use of biorefinery complexity index (BCI) as an indicator of technical and economic risk, algal- and waste-based bio-refinery platforms are considered to be one of the most promising approaches for producing fuel, food, animal feed, food supplements, fertilizers, and pharmaceuticals [10]

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