Two-stage mixotrophic cultivation for enhancing the biomass and lipid productivity of Chlorella vulgaris

Hongwu Cui,Yuejie Wang,Weiyan Duan,Fanping Meng,Feng Li,Yichen Lin

doi:10.1186/s13568-017-0488-9

Hongwu Cui, Yuejie Wang + Show 4 more

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https://doi.org/10.1186/s13568-017-0488-9

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Abstract

This study proposes a two-stage mixotrophic process for cultivating Chlorella vulgaris. Heterotrophic growth is the dominant step in Phase I (to increase microalgal biomass) and photoautotrophic growth occurs in Phase II (to improve biomass concentration and lipid production). The results show that the addition of the low-cost antioxidant sodium erythorbate (8 g L−1) significantly accelerates the growth of microalgae in the first stage with air aeration. Furthermore, a higher CO2 fixation rate was obtained in the second stage (at least 344.32 mg CO2 L−1 day−1) with 10% CO2 aeration. This approximately corresponds to an increase of 177% over simple photoautotrophic cultivation with 10% CO2 aeration during the whole period. The two-stage cultivation strategy achieved a maximum C. vulgaris biomass concentration of 3.45 g L−1 and lipid productivity of 43.70 mg L−1 day−1, which are 1.85 and 1.64 times those arising due to simple photoautotrophy, respectively. Moreover, an analysis of the product’s fatty acid profile indicates that C. vulgaris might be an ideal candidate for two-stage mixotrophic cultivation of a renewable biomass for use in biodiesel applications. Another interesting point to note from the study is that it is an insufficiency of N and CO2 that probably limits the further growth of C. vulgaris.

Highlights

The rapid development of human society and the inexpedient consumption of fossil fuels have caused an energy crisis
The addition of NaE can be clearly seen to have significantly accelerated the growth of C. vulgaris in Phase I as the amount of C. vulgaris in mixotrophic group (MX), mixotrophic group with nitrogen deficiency (MX-N), and MX-C groups increased at a much faster rate from day 1 compared to group photoautotrophic group (PA)
A stationary phase was observed on day 8 in the three mixotrophic groups in Phase I in which the OD680 value remained around 4.8 (~ 1.8 times that observed in the control PA)

Summary

Introduction

The rapid development of human society and the inexpedient consumption of fossil fuels have caused an energy crisis. Huge amounts of greenhouse gases have been emitted into the atmosphere, which have induced unexpected climate changes and global warming. Among these greenhouse gases, carbon dioxide (CO2) is the primary contributor to global warming, accounting for 52% (Wilbanks and Fernandez 2014). Microalgae are the fastest growing plants on earth (able to grow 10–50 times faster than terrestrial plants) and have a very high CO2 fixation rate (Chen et al 2011). It is generally accepted that the combination of CO2 bio-fixation and biofuel production using microalgae is a promising way of realizing a sustainable method of CO2 mitigation (Toledo-Cervantes et al 2013).

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