# Beyond pigments and perfumes: engineering in the carotenoid and apocarotenoid spectrum, novel enzymes, and synthetic biology strategies

## TL;DR

This review explores recent advances in engineering carotenoid and apocarotenoid biosynthesis, focusing on enzymes and synthetic biology strategies to improve production.

## Contribution

The paper provides a pathway module-centric review of novel enzymes and synthetic biology strategies for carotenoid and apocarotenoid biosynthesis.

## Key findings

- Novel enzymatic variants and mutagenesis studies enhance metabolic control in carotenoid biosynthesis.
- Synthetic biology tools and fusion strategies improve pathway modularity across diverse host organisms.
- Recent discoveries highlight gaps and future directions for advancing carotenoid and apocarotenoid production.

## Abstract

Carotenoids and apocarotenoids constitute a structurally and functionally sundry class of isoprenoids whose significance extends from photosynthetic light capture and photoprotection to phytohormone signaling, flavor and aroma formation, and emerging biomedical applications. While recent appraisals have emphasized quantitative advances in microbial production, this mini-review adopts a pathway module-centric perspective. We examine each biosynthetic stage from precursor supply, condensation to geranylgeranyl diphosphate (GGPP), phytoene synthesis, desaturation/isomerization, cyclization, hydroxylation, ketolation, epoxidation, and oxidative cleavage, highlighting novel enzymatic variants, mutagenesis studies, fusion strategies, and compartmentalization approaches that impart metabolic control. Special emphasis is placed on recently discovered and engineered enzymes, as well as synthetic biology tools. This review integrates diverse enzyme sources, host ranges across plants, fungi, algae, yeasts, and bacteria, as well as pathway modularity, to provide an updated review of recent literature. We conclude by outlining future directions that highlight gaps and potential areas for future work. This focused synthesis aims to equip researchers with a hierarchical understanding of the pathways and strategies to advance carotenoid and apocarotenoid biosynthesis.