Inhibition of glucose assimilation in Auxenochlorella protothecoides by light

Yibo Xiao; Jianying Guo; Huachang Zhu; Anwar Muhammad; Haiteng Deng; Zhangli Hu; Qingyu Wu

doi:10.1186/s13068-020-01787-9

Inhibition of glucose assimilation in Auxenochlorella protothecoides by light

Biotechnol Biofuels. 2020 Aug 18:13:146. doi: 10.1186/s13068-020-01787-9. eCollection 2020.

Authors

Yibo Xiao^{1

2}, Jianying Guo³, Huachang Zhu¹, Anwar Muhammad^{1

2}, Haiteng Deng³, Zhangli Hu^{1

4}, Qingyu Wu^{1

3}

Affiliations

¹ Guangdong Technology Research Center for Marine Algal Bioengineering, Guangdong Key Laboratory of Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060 People's Republic of China.
² Key Laboratory of Optoelectronic Devices and Systems of the Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060 People's Republic of China.
³ Key Laboratory of Industrial Biocatalysis of the Ministry of Education and Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing, 100084 People's Republic of China.
⁴ Shenzhen Key Laboratory of Marine Bioresource and Eco-Environmental Science, Longhua Innovation Institute for Biotechnology, Shenzhen University, Shenzhen, 518060 People's Republic of China.

Abstract

Background: The yield of microalgae biomass is the key to affect the accumulation of fatty acids. A few microalgae can assimilate organic carbon to improve biomass yield. In mixotrophic cultivation, microalgae can use organic carbon source and light energy simultaneously. The preference of the main energy source by microalgae determines the biomass yield. Auxenochlorella protothecoides is an oleaginous mixotrophic microalga that can efficiently assimilate glucose and accumulate a large amount of biomass and fatty acids. The current study focused on the effect of light on the growth and glucose assimilation of A. protothecoides.

Results: In this study, we found that the uptake and metabolism of glucose in A. protothecoides could be inhibited by light, resulting in a reduction of biomass growth and lipid accumulation. We employed comparative proteomics to study the influence of light on the regulation of glucose assimilation in A. protothecoides. Proteomics revealed that proteins involving in gene translation and photosynthesis system were up-regulated in the light, such as ribulose-phosphate 3-epimerase and phosphoribulokinase. Calvin cycle-related proteins were also up-regulated, suggesting that light may inhibit glucose metabolism by enhancing the production of glyceraldehyde-3-phosphate (G3P) in the Calvin cycle. In addition, the redox homeostasis-related proteins such as thioredoxin reductase were up-regulated in the light, indicating that light may regulate glucose uptake by changing the redox balance. Moreover, the increase of NADH levels and redox potential of the medium under illumination might inhibit the activity of the glucose transport system and subsequently reduce glucose uptake.

Conclusions: A theoretical model of how glucose assimilation in A. protothecoides is negatively influenced by light was proposed, which will facilitate further studies on the complex mechanisms underlying the transition from autotrophy to heterotrophy for improving biomass accumulation.

Keywords: Biomass; Comparative proteomics; Glucose assimilation; Heterotrophic cultivation; Microalgae.