Harnessing C/N balance of Chromochloris zofingiensis to overcome the potential conflict in microalgal production

Abstract

Accumulation of high-value products in microalgae is not conducive with rapid cell growth, which is the potential conflict in microalgal production. Overcoming such conflict faces numerous challenges in comprehensively understanding cell behavior and metabolism. Here, we show a fully integrated interaction between cell behavior, carbon partitioning, carbon availability and path rate of central carbon metabolism, and have practically overcome the production conflict of Chromochloris zofingiensis. We demonstrate that elevated carbon availability and active path rate of precursors are determinants for product biosynthesis, and the former exhibits a superior potential. As protein content reaches a threshold value to confer survival advantages, carbon availability becomes the major limiting factor for product biosynthesis and cell reproduction. Based on integrated interaction, regulating the C/N balance by feeding carbon source under excess light increases content of high-value products without inhibiting cell growth. Our findings provide a new orientation to achieve great productivity improvements in microalgal production.

Improving ‘Lipid Productivity’ in Microalgae by Bilateral Enhancement of Biomass and Lipid Contents: A Review

“…High lipid content is essential to decrease the processing costs per unit of biomass products, and a high growth rate is required to increase yield per unit culture area. Generally, lipid accumulation in algae typically is not concurrent with a fast growth rate, which is the potential conflict in the production process [58]. To achieve the economically feasible cost at a necessary production scale, it is reasonable to develop an optimal balance among upstream and downstream technologies to reduce overall process costs ( Figure 2).…”

Rapid and Sustainable Conversion of Phenol to Microalgae Biomass

“…Two genes involved in the regulation of the antioxidant enzymes superoxide dismutase, which acts on superoxide and H + to form H 2 O 2 and O 2 , and catalase, which catalyzes H 2 O 2 into O 2 and H 2 O, were downregulated after exposure to environmental stresses such as phenol toxicity, insufficient nutrients, and limited light energy (Table S1). These environmental stresses result in conversion from the photoautotrophic growth of microalgae in the biofilm to heterotrophic growth when there is absence of both light and photocatalytic products (organic carbon sources) due to the genetic transformation of glucose transporter proteins in the outer membrane of microalgae with limited exposure to light energy. , When microalgae suffer from limited light, the main light-harvesting pigments (chlorophyll a and b ) decrease in the biofilm (Figure d), indicating that the energy for cell metabolism under heterotrophic culturing conditions arises from respiratory action . Therefore, more O 2 is converted into ROS by electron transfer of NADPH oxidase.…”

A U-Box Type E3 Ubiquitin Ligase Prp19-Like Protein Negatively Regulates Lipid Accumulation and Cell Size in Chlamydomonas reinhardtii

“…Accumulation of high-value products, including lipid, was against cell growth, and previous studies showed that carbon availability was the major limiting factor for product biosynthesis and cell reproduction. High carbon/nitrogen ratio was capable of stimulating algal cells cycle under nitrogen starvation fed-batch culture condition ( Sun et al, 2020 ). This study suggested that silencing of CrPrp19 caused inhibition of cell cycles (less cell densities, Figure 4A ) and abundance of lipid biosynthesis ( Figure 4B ), which would result from repression in chemical energy consumption by general metabolism that slows down, and the diversion of the chemical energy to conditionally induce metabolism, including TAG synthesis.…”