This study elucidated the role of microalgal proteins, specifically spirulina (SPI), chlorella (CPI), and their equal parts blend, in structuring sodium alginate-based (NaAlg) cryogels and modulating the survivability and adhesion properties of Lacticaseibacillus rhamnosus GG (LGG). All matrices ensured near-complete preservation of LGG during freeze-drying (~10 log CFU g −1 ), reflecting synergistic stabilisation via cryo-concentration, hydrogen bonding, and vitrification within the protein–polysaccharide network. Storage stability was primarily governed by water activity and temperature but was strongly coupled with thermophysical properties: higher glass transition temperatures (T g ) and glassy-state conditions significantly reduced inactivation kinetics, with SPI-based cryogels exhibiting the longest shelf-life (up to 320 days at a w 0.11, 20 °C). During semi-dynamic digestion, protein-dependent colloidal transitions dictated LGG protection and release. SPI systems formed compact gastric aggregates that limited enzyme diffusion and enabled controlled intestinal release, resulting in superior post-digestion viability (~9.6 log CFU g −1 ), whereas CPI and SPI:CPI matrices showed greater losses. These functional differences were mechanistically linked to microstructural features of the cryogels, including highly porous (76–78%) architecture, the protein-specific pore-wall morphology, and aggregation behaviour, despite similar bulk mechanical properties e.g., stiffness and hardness. SPI cryogels preserved LGG cell adhesion to the mucus layer of co-culture model of the intestinal epithelium (4.8 log CFU cm −2 ), showing a strong correlation with post-digestion viability. Overall, microalgal proteins, particularly SPI, govern the interplay between cryogel structure, physical state, and colloidal behaviour. This allows for high lyoprotection, prolonged shelf-life, and improved gastrointestinal survivability and cell adhesion properties, matching or exceeding those of conventional lyophilised microcarriers.
Fortuin et al. (Fri,) studied this question.