Dynamic metabolomic crosstalk between Chlorella saccharophila and its new symbiotic bacteria enhances lutein production in microalga without compromising its biomass

Nutrient stress triggers sugar-mediated carotenoid production in algal-bacterial interactions

This study examined the impact of co-culturing Chlorella saccharophila (UTEX247) with Exiguobacterium sp. strain AMK1 on carotenoid production under nitrate-depleted conditions and 3% CO₂ supplementation. The co-culture significantly enhanced the productivity of lutein (238.31 µg.L⁻¹d⁻¹), zeaxanthin (220.72 µg.L⁻¹d⁻¹), violaxanthin (185.42 µg.L⁻¹d⁻¹), and antheraxanthin (84.07 µg.L⁻¹d⁻¹). Compared to nitrate-repleted mono-cultures, these carotenoids increased by 3.54-fold, 4.81-fold, 12.28-fold, and 9.34-fold, respectively. The violaxanthin cycle, activated by CO₂ supplementation, resulted in higher zeaxanthin production, verified through HPLC analysis. Metabolic profiling highlighted a notable rise in sucrose, an algal-specific metabolite, in the co-culture, reflecting enhanced carbon metabolism and carotenoid synthesis. Conversely, trehalose levels were significantly higher in the bacterial mono-culture (297.77 µg.mL⁻¹) than in the co-culture (88.84 µg.mL⁻¹), showing a 1.68-fold reduction as confirmed by GC-MS/MS. This suggests trehalose as a stress marker, with its reduction indicating mutualistic interactions between algal and bacterial. Overall, the co-culture strategy emerges as a promising approach to activate unexpressed pathways, generate novel metabolites, and enhance yields of valuable carotenoids like lutein and zeaxanthin. This aligns with the principles of a circular bioeconomy, leveraging bacterial biofertilizers, valorizing CO₂, and minimizing chemical dependency, thus offering potential for biorefinery applications.

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.

Microbial Pigments: Major Groups and Industrial Applications

Microbial pigments have many structures and functions with excellent characteristics, such as being biodegradable, non-toxic, and ecologically friendly, constituting an important source of pigments. Industrial production presents a bottleneck in production cost that restricts large-scale commercialization. However, microbial pigments are progressively gaining popularity because of their health advantages. The development of metabolic engineering and cost reduction of the bioprocess using industry by-products opened possibilities for cost and quality improvements in all production phases. We are thus addressing several points related to microbial pigments, including the major classes and structures found, the advantages of use, the biotechnological applications in different industrial sectors, their characteristics, and their impacts on the environment and society.