Improved Productivity of Neutral Lipids in Chlorella sp. A2 by Minimal Nitrogen Supply.

Junying Zhu,Chenliu He,Weixian Chen,Xin Zhang,Hui Chen,Junfeng Rong,Qiang Wang

doi:10.3389/fmicb.2016.00557

Abstract

Nitrogen starvation is an efficient environmental pressure for increasing lipid accumulation in microalgae, but it could also significantly lower the biomass productivity, resulting in lower lipid productivity. In this study, green alga Chlorella sp. A2 was cultivated by using a minimal nitrogen supply strategy under both laboratory and outdoor cultivation conditions to evaluate biomass accumulation and lipid production. Results showed that minimal nitrogen supply could promote neutral lipid accumulation of Chlorella sp. A2 without a significant negative effect on cell growth. In laboratory cultivation mode, alga cells cultured with 18 mg L−1 d−1 urea addition could generate 74 and 416% (w/w) more neutral lipid productivity than cells cultured with regular BG11 and nitrogen starvation media, respectively. In outdoor cultivation mode, lipid productivity of cells cultured with 18 mg L−1 d−1 urea addition is approximately 10 and 88% higher than the one with regular BG11 and nitrogen starvation media, respectively. Notably, the results of photosynthetic analysis clarified that minimal nitrogen supply reduced the loss of photosynthetic capacity to keep CO2 fixation during photosynthesis for biomass production. The minimal nitrogen supply strategy for microalgae cultivation could promote neutral lipid accumulation without a significant negative effect on cell growth, resulting in a significant improvement in the lipid productivity.

Highlights

In the past few decades, the extensive utilization and irreversible depletion of fossil fuels has led to global climate change, environmental pollution, health problems, and an energy crisis (Amaro et al, 2011; Chen et al, 2016)
In order to compare with the cell growth and lipid accumulation in Chlorella cultured under traditional culture conditions, Chlorella sp
In the course of microalgae biodiesel research, numerous reports have revealed that nitrogen deficiency and limitation could increase the lipid content (Jiang et al, 2012; Liu et al, 2012)

Summary

Introduction

In the past few decades, the extensive utilization and irreversible depletion of fossil fuels has led to global climate change, environmental pollution, health problems, and an energy crisis (Amaro et al, 2011; Chen et al, 2016). Extensive use of vegetable oils may cause significant problems, for example, abundance of resource applied to produce fuel will cause starvation in developing countries, and it is important that productive and cultivated land should be used for food instead of fuel production (Paiva and Wolde-Georgis, 2010). Nonfood, source of biological material for biofuel production is microalgae (Day et al, 1999; Qiao et al, 2015), which can be feedstock for biofuel production via photosynthesis by harvesting solar energy and fixing CO2 and convert it into biolipids (Razeghifard, 2013; Chen et al, 2015b). Microalgae are considered to be one of the most promising types of feedstock for making biodiesel (Mata et al, 2010; Chen et al, 2014)

Methods

Results

Conclusion