Metabolic engineering of enhanced glycerol-3-phosphate synthesis to increase lipid production in Synechocystis sp. PCC 6803

Abstract

With the growing attention to global warming and energy sustainability, biosynthesis of lipids by photosynthetic microorganisms has attracted more interest for the production of renewable transportation fuels. Recently, the cyanobacterium Synechocystis sp. PCC 6803 has been widely used for biofuel production through metabolic engineering because of its efficient photosynthesis and well-developed genetic tools. In lipid biosynthesis, glycerol-3-phosphate (G3P) is a key node for both CO2 fixation and lipid metabolism in cyanobacteria. However, few studies have explored the use of G3P synthesis to improve photosynthetic lipid production. In this study, metabolic engineering combined with flux balance analysis (FBA) was conducted to reveal the effect of G3P synthesis on lipid production. Heterologous genes that encoded glycerol-3-phosphate dehydrogenase (GPD) and diacylglycerol acyltransferase (DGAT) were engineered into Synechocystis sp. PCC 6803 to enhance G3P supply and lipid production. The resultant recombinant Synechocystis produced higher levels of lipids without a significant reduction in cell growth. Compared with the wild-type strain, lipid content and productivity of the engineered cyanobacteria increased by up to 36 and 31 %, respectively, under autotrophic conditions. Lipid production under mixotrophic conditions of the engineered cyanobacteria was also investigated. This work demonstrated that enhanced G3P synthesis was an important factor in photosynthetic lipid production and that introducing heterologous GPD and DGAT genes was an effective strategy to increase lipid production in Synechocystis sp. PCC 6803.

Synechocystis sp. PCC 6803 overexpressing genes involved in CBB cycle and free fatty acid cycling enhances the significant levels of intracellular lipids and secreted free fatty acids

“…However, the previous study suggested that overexpression of RuBisCO driven under psbA2 promoter could slightly increase the photosynthesis and biomass yield of Synechocystis PCC 6803 7 . Only few studies have reported the use of Gro3P (glycerol-3-phosphate), a major product of the glpD-catalysed reaction, where Gro3P could ultimately flow to gluconeogenesis, glycolysis and lipid synthesis 9 . The strain overexpressing aas-_glpD_Rubisco (OAGR strain) gave the highest level of intracellular lipid accumulation of approximately 35.9% w/DCW at day 5 of cultivation ( Fig.…”

“…Recent research revealed the enhancement of Gro3P synthesis, which enhanced lipid production in Synechocystis PCC6803, by introducing the heterologous GPD1 gene (encoding glycerol-3-phosphate dehydrogenase) from Saccharomyces cerevisiae and the atf1 gene (encoding diacylglycerol acyltransferase, DGAT) from the oleaginous bacterium Rhodococcus opacus PD630 9 . However, Gro3P also generally functions as a substrate for other pathways including starch and glycogen biosynthesis, isoprene and carotenoid synthesis [9][10][11][12] .…”

Cyanobacteria as an eco‐friendly resource for biofuel production: A critical review

“…PCC 6803 was improved by the expression of GPD1 from Saccharomyces serevisiae and DGAT from Rhodococcus opacus . These genes, which encode glycerol‐3‐phosphate dehydrogenase and diacylglycerol acyltransferase, are the key ones in the lipid metabolism of cyanobacteria …”

Global proteome response ofSynechocystis6803 to extreme copper environments applied to control the activity of the induciblepetJpromoter

“…The carbon partitioning and product yields differ in various growth phases (Wang et al . ; Schuurmans et al . ).…”

“…However, synthesis of foreign compounds has been shown to compete with natural carbon partitioning in growing cells (Schuurmans et al 2017;Giordano and Wang 2018). The carbon partitioning and product yields differ in various growth phases (Wang et al 2016;Schuurmans et al 2017). For instance, enhanced production is obtained by metabolically active cells in the absence of growth (Berla et al 2013).…”