Researchers led by Lihua Zhang and Wei Xu of Xinyang Normal University set out to construct what food scientists call an emulsion gel, a semi-solid material in which tiny oil droplets are trapped inside a three-dimensional gel network. These hybrid materials combine the best of two worlds: like emulsions, they can carry fat-loving nutrients such as beta-carotene; like gels, they resist the gravitational separation, droplet coalescence, and Ostwald ripening that plague ordinary liquid emulsions. The team’s innovation lay in the specific combination of ingredients they chose to build the network: sodium caseinate, a milk protein prized for its emulsifying ability, reinforced by konjac glucomannan and kappa-carrageenan, two polysaccharides with complementary gelling personalities.

Sodium caseinate alone is a workhorse emulsifier in the food industry, but emulsions built solely from it wobble under stress. Shifts in pH, temperature swings, and changes in ionic strength can all destabilize them. Previous work had shown that pairing proteins with polysaccharides produces sturdier systems, because the two classes of molecules interact through hydrogen bonding and hydrophobic interactions, thickening the film that surrounds each oil droplet. Earlier comparisons of four polysaccharides had singled out konjac glucomannan as one of the most effective stabilizers for caseinate emulsions, and kappa-carrageenan had already proven its worth in gels delivering curcumin. What remained unclear was how the two polysaccharides would behave together in a caseinate-based system, and whether their synergy would translate into real protection for beta-carotene.

The fabrication process was deliberately simple, a virtue for any technology hoping to leave the laboratory. Konjac glucomannan was first dispersed in water and stirred for six hours, then sodium caseinate was dissolved into the solution. Camellia oil, a premium edible oil, was blended in at ten percent volume and homogenized at 10,000 rpm for three minutes, producing fine oil droplets coated in protein. Optical microscopy and confocal laser scanning microscopy revealed that the konjac glucomannan made an immediate difference: droplets in the polysaccharide-containing emulsions were smaller and more uniform, and the interfacial film surrounding them was visibly thicker. The added viscosity also slowed droplet movement, reducing the collisions that lead to aggregation.

The next step introduced kappa-carrageenan at four concentrations, from zero to two percent by weight, with the mixtures heated to seventy degrees Celsius to dissolve the polysaccharide and then cooled into gels. Without carrageenan, the system never achieved a solid structure at all, confirming that the protein and konjac alone could not lock the emulsion into place. With carrageenan, the mechanical properties climbed steadily. At the highest concentration, hardness rose by fifty-nine percent, springiness by twenty-seven percent, cohesiveness by seventeen percent, and chewiness more than doubled compared with the lowest carrageenan formulation. The explanation lies in the interpenetration of two networks: konjac glucomannan forms a ductile, flexible scaffold between droplets, while carrageenan contributes a rigid framework, and their entanglement, stitched together by hydrogen bonds, produces a double-network gel far stronger than either component alone.

Water retention proved equally impressive. All three carrageenan-containing gels held their water well during centrifugation, and low-field nuclear magnetic resonance showed that water molecules became progressively less mobile as carrageenan concentration increased. The relaxation signals shifted toward shorter times, indicating that the denser network was immobilizing moisture more effectively. This matters for food applications, because a gel that weeps water loses both texture and shelf appeal. The abundance of hydroxyl and carbonyl groups on konjac glucomannan, which readily form hydrogen bonds with water, combined with the tightening capillary forces of the densifying network, kept moisture locked in place.

Rheological testing traced the sol-to-gel transformation as the samples cooled from seventy to twenty degrees Celsius. The stiffest gel, containing two percent carrageenan, reached its gel point earliest and displayed the highest storage and loss moduli across all temperatures, confirming that more carrageenan raises the gelation temperature and stiffens the final material. Interestingly, creep-recovery experiments showed a trade-off: the softest gel bounced back best after being squeezed, while the stiffest formulations deformed more irreversibly under stress. For designers of functional foods, this tunability is an asset rather than a flaw, allowing texture to be matched to the product, whether a spreadable paste or a sliceable solid.

Electron microscopy provided the most striking visual evidence of the synergy at work. Conventional scanning electron microscopy of freeze-dried gels showed lamella-like structures, but cryo-SEM, which preserves the gel in its native hydrated state, told the real story. Without carrageenan, the structure was loose and irregular, with oil droplets scattered outside a weak network. With carrageenan, the gels reorganized into an orderly honeycomb architecture, with oil droplets nestled uniformly within the pores. At one and a half percent carrageenan, the network reached its peak orderliness, with even pore sizes and well-distributed droplets. Pushing the concentration to two percent actually disrupted the order, suggesting there is a sweet spot where the two polysaccharides are balanced and neither is left unincorporated.

The ultimate test was whether all this structural engineering actually protected beta-carotene, and the answer was a qualified yes. During nine days of refrigerated storage, the gel with one and a half percent carrageenan retained roughly sixty-two percent of its initial beta-carotene, while the carrageenan-free gel retained only about forty-eight percent. The interfacial film of protein and polysaccharide acts as a physical barrier, limiting contact between the carotenoid and water-borne oxidants, while the rigid network restricts molecular mobility within the matrix. Under ultraviolet light, the results were more nuanced. The bulk oil control fared worst, retaining just twenty-seven percent of its beta-carotene after eight hours of irradiation, while the one percent carrageenan gel performed best, its interfacial film effectively shielding the droplets from UV penetration. Unexpectedly, the denser gels with higher carrageenan levels showed somewhat faster photodegradation, likely because their smaller, more finely dispersed droplets presented a larger total surface area to the light.

The study’s authors caution that freeze-thaw stability still needs systematic investigation before these gels reach industrial production, but the implications are already broad. A carrier built entirely from food-grade ingredients, caseinate, konjac glucomannan, kappa-carrageenan, and camellia oil, that can be tuned in texture, holds water tightly, and extends the life of labile nutrients could reshape how functional foods are formulated. The researchers point toward applications in easy-to-swallow gel products for nutritional fortification, a growing need in foods designed for older adults and patients with swallowing difficulties. More broadly, the work demonstrates a principle that resonates across soft-matter science: when two polymers with complementary mechanical characters are woven together, the resulting double network can outperform anything either could achieve alone, and in doing so, it can buy precious time for molecules as fragile as beta-carotene.

Subject of Research: Protein-polysaccharide emulsion gels for protecting beta-carotene

Article Title: Fabrication of sodium caseinate-based emulsions gel with konjac glucomannan and κ-carrageenan for β-carotene protection

Article References: Zhang, L., Li, Z., Yu, S., Wu, G., Xue, J., Li, L., & Xu, W. (2026). Fabrication of sodium caseinate-based emulsions gel with konjac glucomannan and κ-carrageenan for β-carotene protection. Food Chemistry: X, 39, Article 104572. https://doi.org/10.1016/j.fochx.2026.104572

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104572

Keywords: emulsion gels, beta-carotene, sodium caseinate, konjac glucomannan, kappa-carrageenan, food chemistry, nutrient delivery, double-network gel, photostability, camellia oil, functional foods, rheology

The commercial stakes are enormous. The global carotenoid market was valued at 1.44 billion dollars in 2019 and is projected to reach 1.84 billion dollars by 2027, driven by demand for natural antioxidants, pro-vitamin A supplements, and clean-label colorants. Humans cannot synthesize carotenoids themselves, so they must come from diet or supplementation. Beta-carotene, with its two beta-ionone rings, carries full pro-vitamin A activity and supports vision, immune function, and reproduction. Astaxanthin, meanwhile, is a particularly fierce neutralizer of reactive oxygen species, outperforming lutein, lycopene, and beta-carotene in antioxidant assays. These health credentials explain why the pigments command premium prices in nutraceutical and skincare formulations.

Today, most carotenoids come from three routes: chemical synthesis, plant extraction, and microbial fermentation. Chemical synthesis relies on substrates such as acetone, butadiene, and methanol, generating hazardous waste and producing mixtures of stereoisomers, some of which are biologically inactive and face stricter regulatory scrutiny. Plant extraction suffers from low productivity, seasonal variability, and heavy demands on land and water. Fermentation, by contrast, offers year-round production, modest water and nutrient requirements, and the ability to grow microbes on cheap substrates such as lignocellulosic hydrolysates and waste biomass. Companies including DSM Nutritional Products, Cyanotech, AstaReal, Algatech, and Novozymes already use microbial fermentation to produce carotenoids at industrial scale, underscoring that the technology is not merely a laboratory curiosity.

Yeasts are especially attractive hosts because many strains are generally recognized as safe, they grow rapidly in bioreactors, and their genetics and metabolism are exceptionally well characterized. Some yeasts, such as Rhodotorula and Xanthophyllomyces species, naturally produce carotenoids, while workhorse organisms like Saccharomyces cerevisiae and Yarrowia lipolytica do not, but can be engineered to do so. The biosynthetic route runs through the mevalonate pathway: two molecules of acetyl-CoA are condensed to acetoacetyl-CoA, converted through HMG-CoA to mevalonate, and then processed into isopentenyl diphosphate and its isomer dimethylallyl pyrophosphate. These five-carbon building blocks are stitched together into farnesyl pyrophosphate and geranylgeranyl pyrophosphate, the immediate precursors of carotenoids. Phytoene synthase then catalyzes the first colored step, and a cascade of desaturases, cyclases, hydroxylases, and ketolases converts phytoene into lycopene, beta-carotene, zeaxanthin, and ultimately astaxanthin.

Engineering these pathways has produced striking results. Overexpressing the GGS1 gene in Yarrowia lipolytica using CRISPR-Cas9 integration raised beta-carotene titers from 17.1 to 40.4 milligrams per liter, and engineered strains have achieved beta-carotene contents of 4 percent of dry cell weight, several times the concentration found in carrots. Adding extra copies of the ERG13 gene, which encodes HMG-CoA synthase, boosted beta-carotene titers by 259 percent relative to wild type, while duplicating the erg10 gene increased production by 46.9 percent. Feeding hydrophobic substrates such as oleic acid or waste oil helps too, because beta-oxidation of fatty acids raises intracellular acetyl-CoA, the fundamental carbon skeleton from which all carotenoids are built.

Enzyme engineering adds another layer of control. Lycopene cyclase normally suffers from substrate inhibition, diverting flux away from beta-carotene, so researchers screened fifty variants of a bifunctional phytoene synthase/lycopene cyclase and identified a mutant, Y27R, that lost the inhibition entirely. That single change directed carotenoid flux completely toward beta-carotene, yielding an extraordinary 39.5 grams per liter in Yarrowia lipolytica. Directed evolution and adaptive laboratory evolution have also delivered: combining atmospheric and room temperature plasma mutagenesis with hydrogen peroxide-driven selection produced a Saccharomyces cerevisiae strain that reached 404.78 milligrams per liter of astaxanthin in a 5-liter fermenter, the highest reported titer in that organism.

Because carotenoids are hydrophobic molecules stored in lipid bodies, lipid engineering has become a powerful lever. Deleting the POX1 through POX6 beta-oxidation genes and the GUT2 glycerol-3-phosphate dehydrogenase gene in Yarrowia lipolytica enlarged intracellular lipid droplets, expanding storage capacity and pushing lycopene yields to 16 milligrams per gram of dry cell weight in fed-batch culture. Overexpressing lipid synthesis genes such as PAH1, DGA1, and a mutated ACC1 in S. cerevisiae raised both triacylglycerol and lycopene accumulation, confirming a direct correlation between fat storage and pigment yield. Even cell morphology matters: reverting filamentous Yarrowia growth back to yeast form by deleting the CLA4 and MHY1 genes increased beta-carotene production to 7.6 grams per liter, while expanding the endoplasmic reticulum through INO2 overexpression boosted terpene synthesis dramatically.

Yet even the best engineered strains hit ceilings, and this is where metabolomics enters the story. Metabolomic profiling, using techniques such as gas chromatography-mass spectrometry, HPLC-MS, and UPLC-MS/MS, measures the actual chemical state of a cell, capturing the end products of gene expression and regulation more faithfully than transcriptomic or proteomic data. In one study, comparative metabolomics of a recombinant beta-carotene-producing S. cerevisiae strain revealed significant depletion of amino acid, carbohydrate, and TCA cycle intermediates, showing that carotenoid synthesis drains core metabolism. Supplementing the culture with acetate during exponential growth restored intracellular pools and raised beta-carotene production by 39.3 percent. In Rhodosporidium toruloides, time-dependent metabolomics of three strains grown on glycerol showed that the best producer, CBS 5490, achieved 28.5 milligrams per liter by downregulating TCA cycle and amino acid metabolism, effectively redirecting energy and flux toward carotenoid and fatty acid synthesis.

Metabolomics has also illuminated how environmental conditions shape production. In Rhodosporidiobolus colostri, lowering the cultivation temperature to 16 degrees Celsius increased total carotenoids from 17.1 to 29.0 milligrams per liter, and integrated transcriptomic and metabolomic analysis suggested that reduced TCA cycle flux freed acetyl-CoA for beta-carotene and torulene biosynthesis. In engineered lycopene-producing Yarrowia lipolytica, metabolomic comparison with the wild type revealed that lycopene accumulation reshaped fructose and mannose metabolism, the citrate cycle, and glycerophospholipid metabolism, and pointed to shortages of glycerol backbone intermediates rather than fatty acids as the limiting factor for lipid storage. Such insights convert blind strain engineering into rational design, telling researchers precisely which genes to tune and which metabolites to replenish.

The review’s authors argue that cost remains the decisive barrier to commercialization. Expensive carbon sources like glucose inflate fermentation costs, so future work will focus on agricultural byproducts, lignocellulosic biomass, and industrial waste streams as feedstocks, alongside stress-tolerant strains that withstand high temperature, low pH, and high oxygen. Downstream innovations such as enzyme-based cell lysis, membrane extraction, and supercritical CO2 processing promise to cut solvent use and recovery costs. Engineering transporters to export carotenoids could eliminate the need for cell disruption altogether, and hybrid pathways combining the yeast mevalonate route with the bacterial MEP pathway could balance precursor supply and ATP demand. With life cycle assessments and regulatory frameworks still to be established, yeast-derived carotenoids stand at the threshold of replacing synthetic pigments, offering a vision of color and nutrition brewed sustainably in stainless steel tanks rather than extracted from fields or synthesized in chemical plants.

Subject of Research: Metabolomics-guided metabolic engineering of yeasts for cost-effective carotenoid biosynthesis

Article Title: Unlocking yeast’s palette: leveraging metabolomics and gene editing approaches for cost effective carotenoid production

Article References: Arora, N., & Pritam, P. (2025). Unlocking yeast’s palette: leveraging metabolomics and gene editing approaches for cost effective carotenoid production. Blue Biotechnology, 2(1), Article 5. https://doi.org/10.1186/s44315-025-00028-8

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00028-8

Keywords: carotenoids, yeast, metabolomics, CRISPR-Cas9, metabolic engineering, synthetic biology, beta-carotene, astaxanthin, lycopene, Yarrowia lipolytica, Saccharomyces cerevisiae, fermentation

The research team, led by Danhong Ge, YangYang Luo, Ruyu Zhang, Xuechao Hu, and Lujing Ren, set out to answer a deceptively simple question: what happens when you expose a microbe that normally grows in the dark to sustained light stress? Schizochytrium sp. HX-308, the strain used in the study, was isolated from seawater and deposited in the China Center for Type Culture Collection. In industrial settings it is typically fermented in large, dark vessels where it converts glucose into a lipid-rich biomass. Light, in this context, is usually treated as an irrelevance or even a nuisance. The new study suggests that assumption deserves a second look, because light turns out to be a powerful abiotic stress factor that reprograms the cell’s entire metabolic priorities.

The researchers divided the fermentation process into three distinct phases: a cell growth stage from zero to forty-eight hours, a lipid accumulation stage from forty-eight to ninety-six hours, and a lipid turnover stage from ninety-six to one hundred forty-four hours, when the cells begin consuming their own stored fat reserves. Under normal dark conditions, the culture reached a maximum cell dry weight of 50.5 grams per liter at seventy-two hours. When the flasks were illuminated with an array of LED strips delivering a total luminous flux of 18,311.4 lumens, growth slowed noticeably. Glucose consumption was delayed, the fermentation cycle stretched from seventy-two to ninety-six hours, and the peak biomass fell to 41.3 grams per liter, a reduction of 18.21 percent compared with the dark-grown control.

Microscopy revealed that the light-exposed cells were visibly different from their dark-grown counterparts. They grew larger in diameter, became more dispersed and independent in their morphology, and accumulated more prominent lipid droplets as the fermentation progressed. Using propidium iodide staining under a confocal fluorescence microscope, the team showed that cell membrane damage was consistently higher under light stress, peaking at ninety-six hours, precisely when the lipid turnover phase begins. The researchers hypothesize that the enlarged cell diameter is an adaptive response, allowing the organism to meet the elevated energy and material demands imposed by the stressful environment. Similar light-induced changes in cell size have been documented in diatoms such as Ditylum brightwellii, suggesting this may be a widespread strategy among marine microbes.

The real surprise came when the team measured what the cells were actually producing. Although the light-stressed cultures grew more slowly, their final lipid yield reached 8.45 grams per liter, a striking 39.67 percent higher than the 6.05 grams per liter measured in the control after the turnover phase had run its course. The delayed glucose consumption appears to slow the onset of lipid turnover, effectively extending the window during which the cells hold onto their oil. In other words, the stress that cost the microbe some of its growth paid off handsomely in the currency that industry actually cares about: stored lipid that survives to the end of the fermentation.

The composition of that lipid changed too, and in commercially interesting directions. Saturated fatty acids, particularly myristic acid (C14:0) and palmitic acid (C16:0), were 1.49 times more abundant in the light-treated group, reaching 4.97 percent and 15.86 percent of the total fatty acid pool respectively. Saturated fats of this kind are the raw material for neutral lipid formation and have their own market in oleochemical applications. Meanwhile, the polyunsaturated fatty acids docosapentaenoic acid and DHA declined modestly, from 24.74 percent and 59.14 percent in the control to 20.59 percent and 56.28 percent under light. But eicosapentaenoic acid, or EPA, an omega-3 fatty acid with anti-inflammatory applications and a notoriously difficult production process, jumped from 2.14 percent to 8.30 percent of total fatty acids, a 3.88-fold increase that caught the researchers’ attention.

Beyond the fatty acids, light stress proved to be a potent trigger for two of the microbe’s most valuable secondary metabolites. Squalene, a terpenoid used in cosmetics, vaccines, and pharmaceutical formulations, peaked at 67.46 milligrams per liter at seventy-two hours under light stress, compared with 55.67 milligrams per liter at forty-eight hours in the dark, and the light-stressed cultures sustained higher squalene levels through the later stages of fermentation, ending 21.17 percent above the control. Beta-carotene followed a similar pattern, peaking at roughly 7,184 micrograms per liter at ninety-six hours under light versus 5,368 micrograms per liter at seventy-two hours in the dark. By the end of fermentation, the light-stressed cultures contained 5,675 micrograms per liter of beta-carotene, 4.75 times the control level. Astaxanthin, a premium carotenoid synthesized downstream of beta-carotene, rose continuously throughout the light-stressed fermentation, finishing nearly 2,081 micrograms per liter, 11.39 percent above the control, and its accumulation only accelerated after beta-carotene had peaked, consistent with beta-carotene serving as a metabolic precursor.

To understand why light produces these effects, the team measured intracellular reactive oxygen species and performed a full transcriptomic analysis using Illumina RNA sequencing. Light stress elevated oxidative pressure inside the cells, but the light-stressed cultures actually showed lower peak ROS levels than the controls, indicating that the organism mounts a robust antioxidant defense. The transcriptome told the molecular story. A core set of 226 differentially expressed genes was shared across all light-versus-dark comparisons, while the 144-hour comparison alone revealed 788 unique light-responsive genes. At seventy-two hours, light stress predominantly suppressed metabolic genes, an acute stress response; by 144 hours, the pattern flipped to widespread upregulation, signaling a transition to long-term metabolic reprogramming. Gene ontology analysis showed marked enrichment of genes involved in stimulus response, antioxidant activity, and transporter activity under light, while genes for lipid biosynthesis and antioxidant processes became dominant at the later time point.

The pathway-level details are particularly revealing. In the mevalonate pathway, which supplies the building blocks for isoprenoids such as squalene, the enzyme isopentenyl diphosphate isomerase was significantly upregulated under light, especially at 144 hours, along with farnesyl diphosphate synthase and squalene synthase, the enzymes that assemble farnesyl diphosphate into squalene itself. Fatty acid metabolism showed a dual pattern: acetyl-CoA carboxylase and fatty acid synthase were upregulated, driving carbon toward palmitic acid, while a key beta-oxidation gene was downregulated, meaning the cells burned less of the fat they stored. Intriguingly, glycolysis genes were suppressed, suggesting the microbe rerouted carbon flux away from rapid energy production and toward lipid and terpenoid biosynthesis, a strategy that mirrors engineered lipid-boosting interventions in other microalgae. The upregulated polyketide synthase genes hint at the channeling of resources toward EPA production, which supports membrane fluidity under stress.

For the biotechnology industry, the implications are considerable. Light is an inexpensive, non-invasive, and precisely controllable stimulus compared with chemical additives or genetic engineering, and this study demonstrates that it can simultaneously raise lipid yield, enrich EPA, and boost squalene and carotenoid production in a single fermentation run. The trade-off, a longer fermentation cycle and lower biomass, is a real cost, but the researchers argue that the metabolic insights gained here, particularly the coordinated upregulation of the mevalonate pathway and the suppression of fatty acid degradation, could guide further optimization, whether through tuned light regimens, light combined with other stressors, or targeted engineering of the genes identified in the transcriptome. As demand for omega-3 oils and natural antioxidants continues to climb, the idea that a well-placed bank of LED strips could coax more value out of every liter of fermentation broth is an appealingly simple proposition, and one that this marine microbe appears ready to deliver on.

Subject of Research: Effect of light stress on lipid, fatty acid, squalene, and carotenoid biosynthesis in the marine protist Schizochytrium sp.

Article Title: Effect of light stress on the production of lipid compounds by Schizochytrium sp. and its underlying mechanism

Article References: Ge, D., Luo, Y., Zhang, R., Hu, X., & Ren, L. (2025). Effect of light stress on the production of lipid compounds by Schizochytrium sp. and its underlying mechanism. Blue Biotechnology, 2(1), Article 8. https://doi.org/10.1186/s44315-025-00029-7

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00029-7

Keywords: Schizochytrium, light stress, lipid biosynthesis, EPA, DHA, squalene, beta-carotene, astaxanthin, reactive oxygen species, transcriptomics, mevalonate pathway, marine biotechnology

The star of the study was the papaya. Peels from Carica papaya contained 9.03 milligrams of beta-carotene per 100 grams of fresh sample, the highest concentration recorded across all the samples analyzed and well above what was measured in conventional sources such as carrots. Musk melon peels came in a distant second at 3.03 milligrams per 100 grams, while sapota peels registered just 0.67 milligrams. The differences were statistically robust: one-way analysis of variance returned an F value of 1936.623 for this group, and Tukey’s honest significant difference post-hoc test confirmed that all three fruits belonged to distinct categories at p less than 0.001.

Among vegetables, carrot peels led the pack with 1.61 milligrams of beta-carotene per 100 grams, a finding consistent with earlier reports that carrot peels are actually richer in provitamin A than the root flesh itself. German turnip, white radish, and red radish trailed far behind, with red radish registering the lowest value in the entire study at a mere 0.0087 milligrams per 100 grams. The authors attribute this dramatic gap to cellular biology: carrots sequester beta-carotene in crystalline aggregates within chromoplasts, specialized organelles derived from plastids, whereas radish and turnip tissues show limited chromoplast differentiation and low expression of carotenogenic genes such as phytoene synthase and lycopene beta-cyclase.

The banana results added an intriguing varietal twist. Four cultivars procured from a market in Tamil Nadu were compared, and the small Yelakki banana outperformed its larger cousins, delivering 1.84 milligrams of beta-carotene per 100 grams of peel against 1.50 for Red Banana, 1.32 for Nendhran, and 1.01 for Karpoora Valli. The analysis of variance yielded an F value of 63.527 with p less than 0.001. Interestingly, an earlier study on Indian banana cultivars had ranked Red Banana highest, but that work did not include Yelakki or Nendhran, underscoring how much cultivar choice matters when designing waste-valorization strategies. Ripening stage, genetics, growing conditions, and extraction method all influence the final carotenoid tally.

Citrus peels told a similar story of internal diversity. Sweet orange peels contained 1.691 milligrams of beta-carotene per 100 grams, followed by mandarin orange at 1.405, sweet lime at 0.643, and lemon at just 0.222. Every pairwise comparison was statistically significant, splitting the four citrus species into four separate groups. Prior research has shown that carotenoid levels in citrus rise during maturation, with beta-carotene accumulating most prominently in fully ripened peels, and that postharvest storage at ambient temperatures gradually degrades the pigment while controlled environments help preserve it. For food processors weighing whether citrus waste is worth collecting, variety selection and storage conditions could make the difference between a viable ingredient and a worthless one.

The thick rinds of watermelon, pomegranate, and jackfruit fared poorly by comparison, with jackfruit leading the group at only 0.050 milligrams per 100 grams, followed by watermelon at 0.039 and pomegranate at 0.017. Yet the study notes that these tissues are not nutritionally empty: watermelon rind has been reported to contain more beta-carotene than the pulp in certain varieties, and pomegranate rind is loaded with phenolic compounds that may act synergistically with its trace carotenoids. In the cucurbit family, cucumber peel surprised with 0.3713 milligrams per gram, significantly outpacing pumpkin, ash gourd, and bottle gourd, despite the peel’s green color arising from chlorophyll rather than carotenoids. Gene-expression evidence indicates that carotenoid biosynthesis is actively underway in cucumber peel tissue.

Why does any of this matter for human health? Beta-carotene is the most important plant-based precursor of vitamin A, a nutrient essential for vision, immune function, and skin integrity, and it doubles as an antioxidant that neutralizes harmful free radicals. Laboratory studies have even shown that beta-carotene can inhibit cell proliferation, arrest the cell cycle, and promote apoptosis in human breast cancer cell lines. Vitamin A deficiency remains a serious public health problem in many resource-limited regions, contributing to what experts call hidden hunger, a chronic lack of micronutrients even when calorie needs are met. The study’s authors argue that repurposing beta-carotene-rich peels into affordable supplements or food-fortification agents could directly support Sustainable Development Goals 2, 3, and 12, which target food security, well-being, and responsible consumption respectively.

Concentration alone, however, does not guarantee nutritional benefit, and the study is careful to address bioavailability, the fraction of a nutrient the body can actually absorb. Beta-carotene exists in different physical states in plant tissue: as crystals in vegetables like carrots and tomatoes, and as oil droplets in fruits like papayas and mangoes. The oil-droplet form is considerably more accessible to digestive enzymes. Remarkably, a randomized cross-over study cited in the paper found that carotenoid bioavailability from papaya is up to three times higher than from carrots or tomatoes, thanks to papaya’s softer fiber matrix and lower pectin content. Processing matters too: pureeing, chopping, and homogenizing reduce particle size and enhance enzymatic access, while mild heat treatment softens cell structures and disrupts carotenoid-protein linkages. Cooked carrots, for example, raise plasma beta-carotene levels more effectively than raw ones. Excessive heating, prolonged storage, and exposure to light and oxygen, by contrast, degrade the pigment.

The analytical approach itself was deliberately simple and reproducible. Fresh fruits and vegetables were purchased from the Guduvancheri market in Tamil Nadu, washed, manually peeled with sterile knives, and stored at minus 20 degrees Celsius overnight. One-gram samples, weighed in triplicate, were homogenized and extracted with an acetone-hexane mixture in a 4:6 ratio at room temperature under low light, following the classic Nagata and Yamashita method. Absorbance was then measured at four wavelengths, 453, 505, 645, and 663 nanometers, on a UV-Vis spectrophotometer, and beta-carotene content was calculated from a linear combination of those readings. The author acknowledges that future work should validate these spectrophotometric estimates with high-performance liquid chromatography and test how drying, enzymatic pretreatment, and incorporation into functional foods affect the bioavailability of the extracted carotenoid.

The broader significance of the study lies in its framing of food waste as a resource rather than a liability. Fruit and vegetable peels are rich not only in carotenoids but also in polyphenols and dietary fibers with antioxidant and anti-inflammatory properties, and industries ranging from nutraceuticals to cosmeceuticals are actively seeking natural alternatives to synthetic additives. Beta-carotene, in particular, has attracted attention in the cosmetic sector for its role in protecting skin from oxidative stress and reducing visible signs of aging. By demonstrating that a single papaya peel can outperform a carrot as a provitamin A source, the research makes a compelling case for circular-economy thinking in the food-processing sector: instead of paying to dispose of peels, producers could extract value from them, cut landfill burdens, and simultaneously address micronutrient deficiencies. The next challenge, the study suggests, is scaling these laboratory findings into practical extraction pipelines that preserve both the pigment and its bioavailability from farm waste to finished product.

Subject of Research: Beta-carotene content of fruit and vegetable peels as sustainable sources of provitamin A

Article Title: Sustainable waste valorization: harnessing beta-carotene from fruit and vegetable peels

Article References: Alwar, V. (2025). Sustainable waste valorization: harnessing beta-carotene from fruit and vegetable peels. Discover Biotechnology, 2(1), Article 13. https://doi.org/10.1007/s44340-025-00021-2

Image Credits: AI Generated

DOI: 10.1007/s44340-025-00021-2

Keywords: beta-carotene, food waste, fruit peels, vegetable peels, papaya, vitamin A, circular economy, nutraceuticals, carotenoids, sustainability, food waste valorization, functional foods

The study, led by Dishti Dabeedass of the University of Mauritius together with colleagues at Hokkaido University in Japan and Jeju National University in the Republic of Korea, focused on the floating-cage facility at Pointe-aux-Feuilles, operational since 2002 and producing roughly 3,000 tons of fish annually. Fish farming releases feed residues and metabolic waste into the surrounding water, creating a nutrient-enriched micro-ecosystem in the lagoon. These conditions frequently trigger substantial proliferation of opportunistic macroalgae that cling naturally to aquaculture cages, ropes and nets. Rather than treating this growth as a nuisance, the research team asked a different question: what are these seaweeds made of, and could they be worth something?

To find out, the divers hand-collected approximately one kilogram of fresh biomass from each of seven seaweed taxa at depths of no more than two metres, carefully picking from multiple individuals to ensure representative sampling while minimising environmental disturbance. The samples, spanning green, brown and red macroalgal functional groups, were sealed in sterile bags, transported on ice and stored at minus 80 degrees Celsius to preserve their biochemical integrity. Because many tropical macroalgal genera are notoriously plastic in form and include cryptic species that defy visual identification, the team went beyond morphology, extracting genomic DNA and sequencing chloroplast and mitochondrial marker genes, including tufA, psbA, cox3 and rbcL, confirming species identities through nucleotide BLAST searches and depositing the sequences in GenBank.

The molecular work resolved the seven colonisers into a taxonomically diverse line-up: the green seaweeds Ulva torta in its tubular form, Ulva lactuca in its blade form and Caulerpa racemosa; the brown alga Padina sanctae-crucis lineage number two; and the red seaweeds Dasya corymbifera, Hypnea cornuta lineage number three and Gracilaria rangiferina. Each pooled sample was then subjected to a battery of validated Association of Official Analytical Chemists protocols and spectrophotometric assays, quantifying ascorbic acid, total phenolics, total flavonoids, beta-carotene, chlorophyll a and monomeric anthocyanins, with every measurement performed in triplicate.

The headline result came from the green seaweeds. Ulva torta exhibited the highest ascorbic acid concentration at 640 plus or minus 25.6 milligrams per kilogram of fresh weight, with Ulva lactuca and Hypnea cornuta close behind. Green macroalgae, with their chlorophyll-dominated photosynthetic machinery and rapid growth dynamics, are physiologically primed for ascorbate biosynthesis, which serves photoprotection and redox regulation. The authors note that these vitamin C levels are nutritionally significant and comparable to values reported in selected terrestrial plant sources, although direct comparisons warrant caution because of methodological differences. What makes the finding striking is that the biomass was growing passively within a fish farm, without targeted fertilisation or controlled cultivation, demonstrating that nutritionally valuable seaweed can occur naturally within lagoonal environments suited to Integrated Multi-Trophic Aquaculture, or IMTA.

The brown and red algae told a different chemical story. Padina sanctae-crucis dominated the secondary-metabolite league tables, posting the highest total phenolic content at 22.25 plus or minus 5.74 milligrams per kilogram fresh weight and the highest flavonoid content at 398.8 plus or minus 14.6 milligrams per kilogram. Brown algae synthesise phlorotannins, a unique class of polyphenols produced via the acetate-malonate pathway and absent from other algal lineages, compounds that serve antioxidant defence, ultraviolet screening and anti-herbivore protection in shallow, high-irradiance lagoons. The red seaweeds, meanwhile, excelled at carotenoid and pigment chemistry: Dasya corymbifera recorded the highest beta-carotene concentration at 28.18 plus or minus 2.22 milligrams per kilogram fresh weight and the highest chlorophyll a content at 24.00 plus or minus 0.05 milligrams per kilogram, while Dasya corymbifera and Gracilaria rangiferina were the only species with detectable monomeric anthocyanins, at 0.301 and 0.167 milligrams per kilogram respectively.

Statistical analysis confirmed that these differences were far from random. Analysis of variance revealed highly significant species effects across every antioxidant and pigment parameter measured, with effect sizes approaching the theoretical maximum; for chlorophyll a and anthocyanins, species identity explained essentially all of the observed variation. The authors stress an important interpretive caveat, however. Each species was represented by a single composite sample pooled from multiple individuals, so the triplicate assays reflect analytical precision rather than natural within-species variability, and the statistical comparisons describe differences among composite samples rather than estimates of biological variation across populations.

The team is equally candid about the environmental dimension of the work. Although fish farms are commonly associated with localised nutrient enrichment, dissolved nutrient concentrations were not measured during sampling, and no reference populations from non-aquaculture sites were included. The study therefore cannot establish a direct causal link between aquaculture-derived nutrients and the observed antioxidant profiles. Seaweed biochemistry is known to be strongly governed by nutrient availability: under nutrient-replete conditions, macroalgae tend to prioritise growth and accumulate proteins, chlorophylls and water-soluble vitamins such as ascorbic acid, whereas nutrient limitation shifts metabolism toward carbon-rich secondary metabolites like phenolics and flavonoids. Disentangling these nutrient-driven responses will require seasonal sampling, water-quality monitoring and comparative studies across aquaculture and non-aquaculture habitats, priorities the authors lay out for future research.

Even with those caveats, the implications for Mauritius and similar small island developing states are considerable. The global seaweed sector is worth more than eight billion US dollars annually, dominated by Asian producers, yet Mauritius, despite documenting 435 seaweed species and commanding sovereign rights over an Exclusive Economic Zone of nearly 1.9 million square kilometres, harvests seaweed only at limited artisanal scale. In an IMTA framework, seaweeds act as extractive organisms that assimilate dissolved nutrients and improve water quality while generating marketable biomass, and the new biochemical profiles provide a baseline for choosing which species to pair with finfish. Fast-growing green species such as Ulva could supply vitamin C-rich functional food ingredients, brown species like Padina could feed nutraceutical and cosmeceutical pipelines with phlorotannin-rich extracts, and red species such as Dasya corymbifera could serve as marine sources of carotenoids prized for their stability and bioactivity. The research aligns with Sustainable Development Goals 12 and 14 on responsible consumption and marine stewardship, and the authors argue that further work on seasonal variability, nutrient flux dynamics and bioavailability will be needed to translate baseline chemistry into commercial opportunity. For now, the message from the Mauritian lagoon is clear: the structures built to farm fish are also quietly growing some of the ocean’s most biochemically interesting food, and nobody is harvesting it.

Subject of Research: Antioxidant profiles of edible seaweeds colonising lagoonal aquaculture structures in Mauritius

Article Title: Lagoonal aquaculture structures support antioxidant rich edible seaweeds with potential for integrated multitrophic aquaculture in Mauritius

Article References: Dabeedass, D., Akita, S., Vieira, C., Tojo, N., Yao, F., & Nazurally, N. (2026). Lagoonal aquaculture structures support antioxidant rich edible seaweeds with potential for integrated multitrophic aquaculture in Mauritius. Discover Oceans, 3(1), Article 45. https://doi.org/10.1007/s44289-026-00157-x

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00157-x

Keywords: seaweed, aquaculture, Mauritius, antioxidants, vitamin C, IMTA, phlorotannins, beta-carotene, Ulva, blue economy, lagoon, nutraceuticals