Ibtissem Chakroun

The viability and functionality of probiotics are strongly influenced by environmental stressors encountered during processing and storage. This study aimed to evaluate the effects of phycocyanin supplementation and drying in skim milk, followed by vacuum desiccation at 50 °C, on three probiotic strains: Limosilactobacillus reuteri, Lactiplantibacillus plantarum, and Lacticaseibacillus casei. Probiotic viability, metabolic activity, and surface properties were monitored over 12 months of storage at room temperature, refrigeration, and freezing, with assessments performed every three months. Results showed that phycocyanin supplementation markedly improved survival, particularly at room temperature, with increases of up to 2 log CFU/g. Drying in skim milk further enhanced stability and promoted biofilm-forming ability. Additionally, phycocyanin positively affected metabolic activity and cell surface interactions. Overall, these findings demonstrate that combining phycocyanin supplementation with vacuum desiccation in skim milk represents an effective approach for enhancing long-term probiotic preservation under diverse storage conditions.

Bacterial nanocellulose (BNC) has gained considerable interest over the last decade due to its unique properties and versatile applications. However, the low yield and the high production cost significantly limit its industrial scalability. The proposed study explores the isolation of new BNC producers from date palm sap and the use of date waste extract as a sustainable carbon source to improve BNC productivity. Results revealed three potential BNC producers identified as Komagataeibacter sp. IS20, Komagataeibacter sp. IS21, and Komagataeibacter sp. IS22 with production yield of 1.7 g/L, 0.8 g/L and 1.8 g/L, respectively, in Hestrin-Schramm (HS) medium. The biopolymer characterization indicated the presence of type I cellulose, a high thermal stability, and a highly dense network made of cellulose nanofibrils for all BNC samples. The isolate IS22, showing the highest productivity, was selected for an optimization procedure using a full factorial design with date waste extract as a carbon source. The BNC yield increased to 6.59 g/L using 4% date waste extract and 2% ethanol after 10 days of incubation compared to the standard media (1.8 g/L). Two probiotic strains, including Bacillus subtilis (BS), and Lactobacillus plantarum (LP) were successfully encapsulated into BNC matrix through a co-culture approach. The BNC-LP and BNC-BS composites showed antibacterial activity against Pseudomonas aeruginosa. BNC–probiotic composites have emerged as a promising strategy for the effective delivery of viable probiotics in a wide range of applications. Overall, this study supports the use of date waste extract as a sustainable carbon source to enhance BNC productivity and reduce the environmental footprint using a high-yielding producer (IS22). Furthermore, the produced BNC demonstrated promising potential as an efficient carrier matrix for probiotic delivery.

Salmonellosis linked to fish consumption is a significant public health concern. Salmonella often contaminates fish through polluted water or improper handling, with increasing antibiotic-resistant strains in aquaculture. This study evaluated the antimicrobial, antioxidant, and anti-biofilm activities of the cell-free culture supernatant (CFCS) of Limosilactobacillus reuteri against normal and stressed Salmonella Typhimurium in seawater microcosms over four years. The CFCS exhibited minimum inhibitory concentrations (MIC) ranging from 16.66% to 30% under acidic conditions, whereas stressed strains showed increased resistance, with MIC reaching up to 60% at neutral pH. Antioxidant activity reached 38% (DPPH assay), and CFCS significantly reduced biofilm formation and bacterial adhesion by up to 52% on the fish cell line (SAF-1). Additionally, L. reuteri CFCS modulated the expression of genes related to oxidative stress (cat, sod, gr) and immune response (il1b, il6, il8). These findings highlight the potential of L. reuteri CFCS as a natural antimicrobial and anti-virulence agent in marine aquaculture, helping to address antibiotic resistance issues. Graphical abstract

The positive impact of probiotic strains on human health is more evident than ever. To achieve the beneficial health effects and desirable functional properties of probiotics, sufficient numbers of these microorganisms must reach the intestinal tract with high survival rates. The purpose of this study was to identify and characterize a novel strain of Limosilactobacillus reuteri isolated from traditional sheep dry sausage and evaluate its growth-promoting ability with the addition of Arthrospira platensis or phycocyanin extract. In vitro experimental approaches were conducted to determine the physiological features of the candidate probiotic isolate, including biochemical identification, 16S rRNA gene sequencing, tolerance assays to acid and bile salts, antimicrobial activities, adherence ability, and antiproliferative assays. The effects of A. platensis or phycocyanin (0, 1, 5, and 8 mg/mL) on the growth of probiotic cultures were studied after 0, 24, 48, and 72 h. Our results showed that the isolated Limosilactobacillus reuteri (OL468126.1) possesses desirable characteristics as a probiotic candidate and can, therefore, be used as an ingredient in functional foods. Furthermore, A. platensis and phycocyanin extract have great potential for enhancing the growth and prolonging the stationary phase of isolated probiotics. Our findings showed that phycocyanin extract not only plays the role of a natural pigment but also acts as a growth promoter of probiotics.

This study aimed to evaluate the synbiotic effect of probiotics and dried Spirulina platensis or phycocyanin on autoaggregation, coaggregation, and the inhibition of biofilm formation by Salmonella Typhimurium and Staphylococcus aureus on 96-well microtiter plates and Human colon carcinoma cells-116 surfaces. The results showed that the probiotics strains cultured in the presence of S. platensis exhibited the highest autoaggregation values, ranging between 68.5 and 74.2% after 24 h. All probiotic strains with or without S. platensis and phycocyanin showed coaggregation abilities with S. Typhimurium and S. aureus . Interestingly, significant effect of S. platensis and phycocyanin supplementation was observed on the inhibition of the biofilm formation by the selected pathogens during the competition, exclusion, and displacement on abiotic and biotic surfaces.