Microbial chassis as the platform for production of dihydroxy xanthophyll-based carotenoids: an overview of recent advances in biomanufacturing

Physiological and environmental cues prompt microbes to synthesize diverse carotenoids, including dihydroxy xanthophylls, facilitating their adaptation and survival. Lutein and its isomeric counterpart, zeaxanthin, are notable dihydroxy xanthophylls with bioactive properties such as antioxidative, anti-inflammatory, anticancer, and neuroprotective effects, particularly beneficial for human ocular health. However, global natural resources for co-producing lutein and zeaxanthin are scarce, with zeaxanthin lacking commercial sources, unlike lutein sourced from marigold plants and microalgae. Traditionally, dihydroxy xanthophyll production primarily relies on petrochemical synthetic routes, with limited biological sourcing reported. Nonetheless, microbiological synthesis presents promising avenues as a commercial source, albeit challenged by low dihydroxy xanthophyll yield at high cell density. Strategies involving optimization of physical and chemical parameters are essential to achieve high-quality dihydroxy xanthophyll products. This overview briefly discusses dihydroxy xanthophyll biosynthesis and highlights recent advancements, discoveries, and industrial benefits of lutein and zeaxanthin production from microorganisms as alternative biofactories.

Macular Pigment Optical Density Fluctuation as a Function of Pupillary Mydriasis: Methodological Considerations for Dual-Wavelength Autofluorescence

PURPOSE OF THE STUDY

Macular pigment (MP), comprising the dietary carotenoids lutein, zeaxanthin and meso-zeaxanthin, is believed to benefit eye health and vision. Numerous clinical and research devices and techniques are currently available to facilitate MP optical density (MPOD) measurement. One of those techniques, dual-wavelength fundus autofluorescence (AF) is being increasingly used for measurement of MP in the eye. There is substantial methodological variation across the published studies that have employed this technique, including in relation to the use of mydriasis, the possible influence of which does not appear to have been addressed in the literature. This prospective cross-sectional study was designed to investigate the effect of mydriasis on MP measurement quality and MPOD values obtained with dual-wavelength AF using the Heidelberg Spectralis HRA+OCT device.

MATERIALS AND METHODS

Twenty-one healthy participants were recruited to the study. The mean age of participants was 44.8 years (± 14.63). Pupil size and MPOD were measured in one eye for each participant, initially under natural pupil conditions and subsequently 30 minutes following instillation of one drop of 0.5% tropicamide.

RESULTS

Despite providing MPOD measurements for the majority of undilated eyes (85.7% of eyes herein), pupillary dilation resulted in statistically significant changes in MPOD (p < .001 for central eccentricities). Our results indicate that the changes in MPOD were not uniform across the spatial profile. Marked improvements were also observed in image quality post-dilation (p < .002 for central eccentricities).

CONCLUSIONS

This study clearly demonstrates that dual-wavelength AF measurements of MPOD in the same eye vary as a function of pupillary dilation status, with MPOD under-estimated across the entire spatial profile of MP for natural relative to dilated pupillary conditions. Mydriasis should, therefore, be used routinely for MPOD measurements using dual wavelength AF, pupil size should be reported and image quality optimized in order to ensure accurate MPOD quantification.