Salwa Karboune

This work aims to characterize the bioactive metabolite profile and in vitro multifunctional properties of postbiotic cell-free supernatants (Postbiotic-CFSs) derived from three lactic acid bacteria (Levilactobacillus brevis S27, Lactiplantibacillus pentosus S42, and Lactiplantibacillus plantarum S62) isolated from fermented green olives. The postbiotic-CFSs were analyzed for their bioactive metabolites, emulsification index E24%, and antimicrobial, antioxidant, anti-inflammatory, and antidiabetic activities. The bioactive metabolites identified in all postbiotics included organic acids (lactate, citrate, and oxalate), SCFAs (acetate), hydrogen peroxide, diacetyl, exopolysaccharides (EPSs), proteins, biosurfactants, polyphenols, and flavonoids. The postbiotic-CFSs exhibited emulsification index (E24%) values ranging from 21.5% to 38.2%. Furthermore, they demonstrated antimicrobial properties with inhibition diameters ranging from 14.10 to 16.9 mm against pathogenic bacteria and from 15.8 to 23.50 mm against yeast, while fungal mycelial growth was inhibited by 35.77 to 45.09%. All postbiotics demonstrated antioxidant activities of DPPH from 65.91 to 68.55% and FRAP values from 1707.31 to 1765 µg AAE/mL, as well as anti-inflammatory activity (11.83–12.88%) and antidiabetic activity (34.38–93.75%). These findings highlight the significant potential of postbiotic-CFSs as natural bio-preservative agents in food products and as a source of bioactive metabolites with multifunctional health benefits for consumers.

Fermentation offers a promising strategy for the valorization of fruit by-products (FBPs), but its effectiveness largely depends on the selection of functionally suitable and safe microbial strains. In this study, a total of 174 native isolates from FBPs underwent parallel phenotypic profiling and genotype-level evaluation, providing complementary insights into their functionality and safety. The multi-criteria screening approach enabled the identification of four isolates (Bacillus subtilis W46, B. licheniformis C36, B. licheniformis A14, and Latilactobacillus curvatus W47) with high potential for the fermentation of FBPs. These strains exhibited high compatibility with fruit matrices, broad enzymatic activities, and susceptibility to clinically relevant antibiotics. Genomic analysis also revealed genes encoding diverse CAZyme families, while the absence of virulence factors and acquired antibiotic resistance genes further supported their biosafety. Among the selected isolates, B. licheniformis A14 was successfully applied for apple pomace fermentation, with pH adjustment proving critical for bacterial proliferation, metabolic conversion, and functional modification of the substrate. Under near-neutral conditions, fermentation enhanced carbohydrate assimilation, volatile organic acid production, phenolic release, and antioxidant activity, while reducing several intrinsic non-volatile organic acids. Overall, these results establish a structured multi-criteria screening strategy for selecting promising candidates that enable the sustainable valorization of FBPs, offering a transferable framework for safe and efficient fermentation-based valorization of food waste and by-products.

Conventional agar-based direct-plating assays are widely used to screen microorganisms for enzyme production, but their applicability can be limited, particularly by interference from complex growth media. We developed an ammonium sulfate-assisted agar well diffusion method that separates microbial cultivation from extracellular enzyme detection. Enzymes recovered from culture supernatants are concentrated and tested on substrate-containing agar without a nutrient-rich growth medium. Commercial reference enzymes produced concentration-dependent reaction zones and calibration curves for quantitative analysis of isolate-derived activities. Application to fruit by-product isolates W46 and W47 demonstrated distinct enzyme activity profiles and the method’s practical utility. However, W46 lipase activity detected by direct plating was not recovered after precipitation, indicating enzyme-dependent recovery and the need to optimize precipitation conditions for specific targets. Overall, the method provides a practical screening alternative with reduced contamination risk when conventional direct plating is unsuitable or insufficiently informative.Separates cultivation from enzyme detection, reducing interference from complex growth media, preventing substrate-related growth inhibition, and facilitating visualization of substrate hydrolysis.Concentrates extracellular enzymes and increases enzyme–substrate contact, improving sensitivity to low levels of enzyme production.Enables quantitative expression of microbial enzyme activity as reference-enzyme equivalents.

A pilot plant extraction process successfully produced oligo and polysaccharide-rich extracts from Sidestream cranberry pomace using hot water (WE), alkaline (AE), and enzymatic extraction (EE-> 5 kDa and EE-< 5 kDa) approaches. The characterization of these extracts was assessed in terms of carbohydrate yield, monosaccharides profile, and molecular weight distribution. Carbohydrates contents resulted in WE (74.5%), EE-< 5 kDa (66.7%), EE-> 5 kDa, (58.7%), and AE (42.5%) with predominant neutral sugars-based polysaccharides. WE and AE yielded pectic polysaccharides indicated by the proportion of rhamnose (1.3, 1.7%), arabinose (13.8, 22.7%), galactose (8.8, 13.8%), and galacturonic acid (29.2, 12.5%), respectively. While EE-> 5 kDa and EE-< 5 kDa, exhibited the predominant presence of hemi-cellulosic polysaccharides with proportions 53.3 and 82.2% signified by the proportion of glucose (39.3, 69.9%) and xylose/mannose (14, 12.2%), respectively. High molecular weight polysaccharides (>300 kDa) and (100-300 kDa) were abundant in AE, while oligosaccharides (0.5-3kDa) were enriched in WE (53.2%), EE-> 5 kDa (56.6%), and EE-< 5 kDa (83.25%). Further assessment of techno-functional properties of carbohydrate extracts was also conducted. Alkaline extracts exhibited promising emulsifying properties at a 0.01% concentration and demonstrated a higher oil-holding capacity (8.2 g/g) compared to both citrus pectin (2.2 g/g) and rhamnogalacturonan (4.5 g/g). Water and enzymatic extracts exhibited oil-holding capacities comparable to rhamnogalacturonan. Enzymatic extract demonstrated the highest foaming capacity, while WE and AE showed foaming capacities similar to that of citrus pectin.

The compositional profiles of 163 Canadian honey samples from four botanically sources—buckwheat, clover, goldenrod, and blueberry—were analyzed for enzymatic activity and sugar composition using spectrophotometry and LC-QToF-MS. Results showed that clover and goldenrod honeys exhibited higher diastase and invertase activities (11.90DN/4.24IN and 12.52DN/5.33IN), while buckwheat honey displayed the highest acid phosphatase activity (683.20mgP/100g). Blueberry honey demonstrated elevated glucose oxidase and catalase activities (11.84 μgH2O2/g/h and 27.63 μgH2O2/g/ min). Fructose and glucose concentrations ranged from 37.0–38.1%(w/w) and 32.0–34.1%(w/w), respectively, across the four floral types, with maltose identified as the most abundant disaccharide. Multivariate analysis assessing the variables observed negative correlations between diastase and HMF (p≤0.0001) as well as between glucose and nigerose, isomaltose, or gentiobiose content (p≤0.0001). The predictive models for botanical origin classification achieved an accuracy of 80%–90%. Acid phosphatase and catalase were identified as the most impactful features to differentiate clover, blueberry, and buckwheat honey across various models.