Analysis of iron and nitrogen interplay in lipids accumulation in microalgae

Author(s)

Delaram Taghavi

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2022-03-04

Examining board members

Flavia Vischi Winck; Thiago Olitta Basso; Telma Teixeira Franco; Ana Teresa Lombardi

• Advisor: Flavia Vischi Winck

Abstract

Increasing the world population, emission of greenhouse gasses and global energy demand has led to the quest for a sustainable and renewable source of energy. Microalgae have been identified as a prospective source of biofuel production due to a large number of microalgae species that boast the ability to produce a large amount of neutral lipids, such as triacylglycerols (TAGs), under stress such as light, pH, temperature, salt, and nutrient stress or biotic stresses. One of the most conspicuous nutrients stresses that have been accentuated is nitrogen deprivation which is known to trigger TAGs accumulation inside the microalgae cell. On the downside, this stress condition impacts the cell growth and consequently decreases microalgae\'s applicability as a bioenergy and lipids feedstock for biotechnological purposes such as biofuel production. Supplementing the culture with nutrients is an approach that has been utilized to improve the growth and biomass of microalgae cells. As it has been shown, with iron supplementation the growth and lipid content were enhanced in microalgae culture. However, there is still no comprehensive understanding of the in-depth mechanism of this cellular response and the function of iron in enhancing the TAG accumulation and the iron and nitrogen interaction mechanism which seems to lead toward improving growth and increasing lipid accumulation. Recently, optimizing the culture condition for better growth and TAG production has been a very important subject as microalgae became a promising sustainable source. Therefore, to investigate the cellular responses of microalgae to the interplay of iron supplementation and nitrogen deprivation and to explore the interaction effect of these two nutrients on lipid accumulation and growth on Chlamydomonas reinhardtii, a Central Composite Rotatable Design (CCRD) was carried out. Mass spectrometry-based proteomics has become an integral part of the systems biology. In this study, in the model species microalgae C. reinhardtii, mass spectrometry-based Label-free time-resolved quantitative shotgun proteomics analysis of multiple experimental conditions showed the identity of proteins that may involve in nitrogen and iron interaction in the modulation of cell growth and TAGs accumulation. The results illustrate that the abundance of proteins involved in photosynthesis, oxidation-reduction processes, and polyamine biosynthesis was significantly modulated by the interplay between iron and nitrogen while maintaining the cells\' growth performance and lipid levels high. Although manipulating the micronutrients and macronutrients in the culture medium would cause stress and consequently increase the reactive oxygen species (ROS) production, it seems that this interaction could decrease the ROS levels inside the cell which results in an equilibrium between growth and lipid accumulation. (AU)

• FAPESP's process: 17/23674-8 - Analysis of iron and nitrogen interplay in lipids accumulation in microalgae
• Grantee: Delaram Taghavi
• Support Opportunities: Scholarships in Brazil - Doctorate