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Abstract BACKGROUNDHaematococcus pluvialis(Hp), a freshwater chlorophyte microalga, is a major natural source of astaxanthin (ASX), a potent antioxidant with anti‐inflammatory, anticarcinogenic and muscle pigmentation properties. However,ASXbioavailability is limited by the rigid cyst wall and, although cell wall rupture improves bioavailability, the free form is unstable under high temperatures,pHextremes, light or oxygen. Encapsulation techniques improveASXstability, making it suitable for functional foods and aquaculture, especially in salmonid feeds where natural pigments are preferred. The present study evaluates the stability of weakenedHp(Hpw) biomass encapsulated in alginate (ALG) via ionic gelation. RESULTSEncapsulation utilizingALGachieved high efficiency (97 ± 2.63%) and loading capacity (32 ± 0.90%), confirming its suitability as a wall material.ALG‐Hpwhydrogels displayed significant color intensity, enhancing potential feed or food hues. Low bulk density (0.59 ± 0.01 g cm−3), moisture content (11.97 ± 0.20%) and water activity (0.28 ± 0.00) suggest minimized oxidation processes. Hydrogels measured 1.30 ± 0.06 mm with a uniform sphericity factor of 0.058 ± 0.03. Confocal laser scanning microscopy confirmed uniformHpwdistribution andscanning electron microscopyrevealed fissure‐free surfaces, ensuring minimal permeability. DPPH (i.e. 2,2‐diphenyl‐1‐picrylhydrazyl) scavenging activity was similar betweenHpwextract (38.32 ± 2.30% to 96.32 ± 0.88%) andALG‐Hpwhydrogels (33.20 ± 1.55% to 93.30 ± 0.44%).ALGIncreasedHpwdecomposition temperature by 40.97 °C. Encapsulation ofHpwinALGsignificantly enhanced the bioaccessibility ofASX. TheALG‐based encapsulation effectively preservedASXstability, retaining over 90% of its content under storage conditions. CONCLUSIONALGis a suitable biopolymer for encapsulatingHpw, preserving antioxidant activity, and enhancing thermal properties, making it valuable for broader applications. © 2025 Society of Chemical Industry.
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This content will become publicly available on February 19, 2026
High-pressure continuous culturing: life at the extreme
ABSTRACT Microorganisms adapted to high hydrostatic pressures at depth in the oceans and within the subsurface of Earth’s crust represent a phylogenetically diverse community thriving under extreme pressure, temperature, and nutrient availability conditions. To better understand the microbial function, physiological responses, and metabolic strategies atin-situconditions requires high-pressure (HP) continuous culturing techniques that, although commonly used in bioengineering and biotechnology applications, remain relatively rare in the study of the Earth’s microbiomes. Here, we focus on recent developments in the design of HP chemostats, with particular emphasis on adaptations for delivery and sampling of dissolved gases. We present protocols for sterilization, inoculation, agitation, and sampling strategies that minimize cell lysis, applicable to a wide range of chemostat designs.
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- Award ID(s):
- 1951673
- PAR ID:
- 10629056
- Editor(s):
- Biddle, Jennifer F
- Publisher / Repository:
- American Society for Microbiology
- Date Published:
- Journal Name:
- Applied and Environmental Microbiology
- Volume:
- 91
- Issue:
- 2
- ISSN:
- 0099-2240
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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