Abstract
Heme is an iron-containing compound with important applications in food technology, nutrition, and medicine. In addition to contributing meat-like colour and flavour, heme can serve as a natural alternative to nitrite curing agents and as a highly bioavailable iron source for addressing iron-deficiency anaemia. Growing demand for sustainable heme production has increased interest in microalgae and cyanobacteria as alternative production platforms due to their rapid growth, photosynthetic efficiency, and natural capacity for tetrapyrrole biosynthesis. However, studies directly investigating heme accumulation and targeted pathway engineering in these organisms remain limited.
This review summarizes current knowledge of tetrapyrrole and heme biosynthesis in microalgae and cyanobacteria, with an emphasis on key enzymatic and regulatory steps influencing heme production. Potential engineering targets across the pathway are discussed. Because direct heme-focused studies in microalgae are still scarce, insights are partly informed by advances in engineering related metabolites and by metabolic engineering strategies established in bacteria and yeast.
Strain improvement approaches are discussed, including random mutagenesis and genetic engineering, together with current limitations related to genetic tools, pathway regulation, and large-scale cultivation. Overall, this review highlights current knowledge gaps and summarizes potential strategies for support of efforts to improve heme production in microalgae and cyanobacteria.
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