The consumption of microalgae-based foods is growing due to their exceptional nutritional benefits and sustainable cultivation. However, their strong off-flavors and odors hinder their incorporation into food products. Lactic acid fermentation, a traditional method known for modifying bioactive and aromatic compounds, may address these challenges. This study aims to evaluate the impact of lactic acid fermentation on the aromatic profiles of four distinct Chlorella vulgaris biomasses, each varying in protein, carbohydrate, lipid, and pigment content. Six lactic acid bacteria (LAB) strains, Lacticaseibacillus casei, Lcb. paracasei, Lcb. rhamnosus, Lactiplantibacillus plantarum, Lactobacillus delbrueckii subsp. bulgaricus, and Leuconostoc citreum, were used for fermentation. All biomasses supported LAB growth, and their volatile profiles were analyzed via HS-SPME-GC-MS, revealing significant variability. Fermentation notably reduced concentrations of compounds responsible for off-flavors, such as aldehydes. Specifically, hexanal, associated with a green and leafy aroma, was significantly decreased. Lcb. paracasei UPCCO 2333 showed the most effective modulation of the volatile profile in Chlorella vulgaris, significantly reducing undesirable compounds, such as aldehydes, ketones, pyrazines, and terpenes, while enhancing ester production. These results highlight lactic acid fermentation as an effective method to improve the sensory characteristics of C. vulgaris biomasses, enabling their broader use in innovative, nutritionally rich food products.

The demand for functional beverages with clean labels is growing. Arthrospira platensis and fermented products offer bioactive compounds, including antimicrobials. This study aimed to produce food-grade extracts from lactic acid-fermented A. platensis and evaluate its antimicrobial activity, lipid-reducing and glucose uptake effects, and antioxidant properties. An in situ test was also conducted to assess antimicrobial activity in commercial soft drinks against Escherichia coli. Arthrospira platensis was fermented with five different QPS LAB strains: Limosilactobacillus fermentum UPCCO 1986, Companilactobacillus farciminis UPCCO 4841, Levilactobacillus brevis UPCCO 4873, Lentilactobacillus diolivorans UPCCO 5571, and Latilactobacillus curvatus UPCCO 6133, obtaining good results in aerobic and anaerobic conditions. The results have shown that the most versatile strain in fermenting biomass is L. brevis UPCCO 4873. Important in vitro antimicrobial activity was seen against Salmonella enterica, Listeria monocytogenes, Staphylococcus aureus and Escherichia coli. The extracts that exerted the highest antimicrobial activity (4841AE/AN, 5571AE, and 6133AN) were assessed for the in situ antimicrobial activity against E. coli ATCC 11229. Overall, the antimicrobial activity of the extracts was concentration-dependent, with higher concentrations exhibiting bactericidal effects and lower concentrations displaying bacteriostatic effects. Extracts from fermented A. platensis have also significantly reduced the neutral lipid reservoirs, which were not observed without fermentations. The strongest lipid-reducing effect was obtained with A. platensis fermented with Levilactobacillus brevis UPCCO 4873. This work opens the possibility of developing bioactive extracts or natural preservatives from fermented microalgae to be used in novel functional beverages.