Abstract
Chemically synthesized retinyl palmitate has been widely used in the cosmetic and biotechnology industry. In this study, we aimed to demonstrate the microbial production of retinyl palmitate and the benefits of microbial retinyl palmitate in skin physiology. A heterologous retinyl palmitate biosynthesis pathway was reconstructed in metabolically engineered Escherichia coli using synthetic expression modules from Pantoea agglomerans, Salinibacter ruber, and Homo sapiens. High production of retinyl palmitate (69.96 ± 2.64 mg/L) was obtained using a fed-batch fermentation process. Moreover, application of purified microbial retinyl palmitate to human foreskin HS68 fibroblasts led to increased cellular retinoic acid-binding protein 2 (CRABP2) mRNA level [1.7-fold (p = 0.001) at 100 μg/mL], acceleration of cell proliferation, and enhancement of procollagen synthesis [111% (p < 0.05) at 100 μg/mL], strongly indicating an anti-ageing-related effect of this substance. These results would pave the way for large-scale production of retinyl palmitate in microbial systems and represent the first evidence for the application of microbial retinyl palmitate as a cosmeceutical.
Highlights
Vitamin A derivatives include a number of related nutritional hydrophobic compounds, such as retinal, retinol, retinoic acid, and several retinyl esters
Vitamin A consists of three structural domains: a cyclic moiety, a polyene side chain, and a polar end group. β-carotene is converted in vivo into vitamin A derivatives through the addition of functional groups, such as a hydroxyl in retinol, an aldehyde in retinal, a carboxylic acid in retinoic acid, and an ester in retinyl ester [3]
Given that the major rate-limiting enzymes of the MEP and IPP pathways are 1-deoxyxylulose 5-phosphate synthase (DXS), 1-deoxyxylulose 5-phosphate reductoisomerase (DXR), isopentenyl diphosphate isomerase (IDI), and farnesyl diphosphate synthase (IspA) [34], the four genes encoding these enzymes were individually engineered to serve as an expression module and integrated into the genome of an E. coli strain
Summary
Vitamin A derivatives include a number of related nutritional hydrophobic compounds, such as retinal, retinol, retinoic acid, and several retinyl esters. Β-carotene is converted in vivo into vitamin A derivatives (retinoids) through the addition of functional groups, such as a hydroxyl in retinol, an aldehyde in retinal, a carboxylic acid in retinoic acid, and an ester in retinyl ester [3]. In the case of retinol biosynthesis, cytoplasmic retinol-binding protein (CRBP) accepts retinol for retinol storage and homeostasis in vivo before esterification for the synthesis of retinyl esters [6]. Retinyl ester, a storage form of retinol, is synthesized via esterification of a fatty acyl group to the hydroxyl terminus of retinol; this reaction is catalyzed by lecithin retinol acyltransferase (LRAT) [7]
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