The assimilation of glycerol into lipid acyl chains and associated carbon backbones of Nannochloropsis salina varies under nitrogen replete and deplete conditions

Abstract

Mixotrophic cultivation can increase microalgae productivity, yet the associated lipid metabolism remains mostly unknown. Stable isotope labeling was used to track assimilation of glycerol into the triacylglyceride (TAG) and membrane lipids of Nannochloropsis salina. In N-replete media, glycerol uptake and 13 C incorporation into acyl chains were, respectively, 6-fold and 12-fold higher than in N-deplete conditions. In N-replete cultures, 42% of the carbon in the consumed glycerol was assimilated into lipid acyl chains, mostly in membrane lipids rather than TAG. In Ndeplete cultures, only 11% of the limited amount of consumed glycerol was fixed into lipid acyl chains. Labeled lipid-associated glycerol backbones were predominantly 13 C 3 labeled, suggesting that intact glycerol molecules were directly esterified with fatty acids/polar head groups. However, the presence of singly and doubly labeled lipid-bound glycerol species suggested that some glycerol also went through the central carbon metabolism before forming glycerol-3-phosphate destined for lipid esterification. 13 C incorporation was higher in the saturated and monounsaturated than the polyunsaturated acyl chains of TAG, indicating the flux of carbon from glycerol went first to de novo fatty acid synthesis before acyl editing reactions. The results demonstrate that nitrogen availability influences both glycerol consumption and utilization for lipid synthesis in Nannochloropsis, providing novel insights for developing mixotrophic cultivation strategies.

A minireview on the bioremediative potential of microbial enzymes as solution to emerging microplastic pollution

“…It was found that the hydrolytic action involves the activation of a catalytic triad following the formation of tetrahedral intermediates that stabilizes the enzyme structure (Yoshitake et al, 2009). Hydrolysis produced volatile fatty acids and glycerols that eventually assimilated by the microorganisms to yield lipid acyl chains for cell membrane maintenance (Poddar et al, 2020). Bacterial lipases are also recognized for breaking down plastic polymers like polyurethane (Gautam et al, 2007) and PET oligomers (Swiderek et al, 2022).…”