EVALUATION OF PHYSIOLOGICAL FUNCTIONS OF FREEZE-DRIED PROBIOTICS WITH MICROALGAE BIOMASSES DURING STORAGE

Probiotics are usually marketed as freeze-dried powders. Polysaccharides and
oligosaccharides are used to avoid dehydration and cell membrane rupture during freeze-drying,
increasing the survival and stability of probiotics over the storage. Microalgae biomasses contain large
amounts of fiber and oligosaccharides, however, they are not exploited as probiotic protectors. Thus,
the aim was to evaluate physiological functions (membrane integrity and efflux activity) of freeze-dried
probiotics with microalgae biomass during refrigerated storage. Fresh suspensions of Lactobacillus
acidophilus 05 (La-5) and Lacticaseibacillus casei 01 (Lc-1) (10 mL; 10 log CFU/mL) were mixed with 1 g
of biomass of Chlorella vulgaris (CV) and Lagerheimia longiseta (LL). Samples were freeze-dried at 55
± 2°C for 40 h, sealed in polypropylene bags and stored at 4 °C for 120 days. Freeze-dried probiotics
without microalgae were used as a control. Probiotics were enumerated onto MRS agar with a
detection limit of 1.5 log CFU/g. Membrane integrity and efflux activity were evaluated in a flow
cytometer using propidium iodide and ethidium bromide, respectively. At 120 days of storage, freezedried Lc-1 with CV showed less reduction in counts (0.9 log CFU/g) than freeze-dried Lc-1 with LL (1.72
log CFU/g). The opposite was observed for La-5 (1.4 and 0.9 log CFU/g). Lc-1 (8.9 %) and la-5 (8.6 %)
freeze-dried with LL had smaller populations with compromised efflux activity in relation to the
controls(92.9 to 99.4 %). The microalgae biomass used reduced damage to probiotic membranes (12.5
to 59.2 %) compared to the control (82.1 to 86.6 %). Cryoprotection varies with the microalgae species
and probiotic culture tested. The most promise results were achieved with La-5 freeze-dried with LL.