Hakim Belkhalfa

Biofilm formation is a major contributor to antibiotic resistance in Klebsiella pneumoniae, posing a serious challenge to current therapeutic strategies. Thus, this study aims to evaluate the antibiofilm activity of three essential oils Thymus hirtus Willd. Ssp. algeriensis Boiss, Syzygiuma romaticum, and Eucalyptus globulus against four clinical isolates of ESBL-producing K. pneumoniae, along with the reference strain K. pneumoniae ATCC 700603. The antibiofilm activity of essential oils was assessed with crystal violet assay using MICs ranging from 3.38 ± 0.2 to 27.1 ± 0.56 mg/mL, 2 ± 0.19 to 32 ± 0.55 mg/mL, and 13.78 ± 0.62 to 110.25 ± 3.37 mg/mL, for TEO, SEO and EEO, respectively. In vitro tests showed that S. aromaticum EO and T. algeriensis EO exhibited the best anti-adhesive activity with a percentage of up to 75.39%, while no difference was observed between the EO in their eradication activity. Microscopic observations confirmed the disorganization of the biofilm after treatment with T. algeriensis. The molecular docking analysis of the three EOs main compounds with MrkH, SdiA and MrkD revealed that SdiA was the most favorable target, with p-cymene (−7.7 kcal/mol), α-pinene (−7.5 kcal/mol), and eucalyptol (−7.1 kcal/mol) showing the strongest binding affinities. Thymol and p-cymene showed also a favorable affinity with MrkD. Overall, p-cymene and α-pinene demonstrated the most favorable binding profiles, whereas linalool exhibited the weakest predicted interactions. These results highlight the promising potential of these EOs, as multi-target antibiofilm agents against MDR- K. pneumoniae biofilms.

Microalgae-based bioremediation is increasingly recognized as a sustainable, efficient, and straightforward technology. Despite this growing interest, the potential of Parachlorella hussii for metal biosorption remains underexplored. This study is the first report evaluating the metal biosorption activity in Parachlorella hussii ACOI 1508 (N9), highlighting the impact of the culture age on the monosaccharide composition and its correlation to the metal binding capacity. The capsular strain (N9) was isolated from the hypersaline ecosystem—Lake Chott Aïn El-Beida—in southeastern Algeria. Cultivated in Bold’s Basal medium, the strain produced 0.807 ± 0.059 g L⁻¹ of RPSs and 1.975 ± 0.120 g L⁻¹ of CPSs. Biochemical analysis of the extracts revealed a high total sugar content (% w/w) that ranged from 62.98 ± 4.87% to 95.60 ± 87% and a low protein content (% w/w) that ranged from 0.49 ± 0.08% to 1.35 ± 0.69%, with RPS-D7 and RPS-D14 having high molecular weight (≥2 MDa). HPLC-based monosaccharide characterization demonstrated compositional differences between the exponential and stationary phases, with rhamnose dominating (~55%) in RPS-D14 and with the presence of uronic acids comprising 7–11.3%. Metal removal efficiency was evaluated using the whole biomass in two growth phases. Copper uptake exhibited the highest capacity, reaching 18.55 ± 0.61 mg Cu g⁻¹ DW at D14, followed by zinc removal with 6.52 ± 0.61 mg Zn g⁻¹ DW. Interestingly, removal efficiencies increased to about twofold during the stationary phase, reaching 51.15 ± 1.14% for Cu, 51.08 ± 3.35% for Zn, and 36.55 ± 3.09% for Ni. The positive results obtained for copper/zinc removal highlight the biosorption potential of P. hussii, and notably, we found that the metal removal capacity significantly improved with culture age—a parameter that has been poorly investigated in prior studies. Furthermore, we observed a growth phase-dependent modulation in monosaccharide composition, which correlated with enhanced functional properties of the excreted biomolecules involved in biosorption. This metabolic adjustment suggests an adaptive response that may contribute to the species’ effectiveness in heavy metal uptake, underscoring its novelty and biotechnological relevance.

Cellulose is the most abundant and renewable polymer in nature. It is characterized by its biodegradability which helps create a friendly environment. This study seeks to describe the nanocellulose obtained from waste date palm, within the dried palms (DP) and the fresh palms (FP) through implementing chemical methods (hydrolysis with H2SO4). Physical properties, morphology, the elemental composition and the thermal stability were determined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), zeta sizer, scanning electron microscopy (SEM), whereas energy dispersive X-ray (EDX) and thermogravimetric analysis (TGA), respectively. FTIR, SEM and EDX results revealed the effective removal of impurities, hemicellulose and lignin. After treatment, the dried palm (DR) samples contained 35.99% of cellulose and 33.12% of cellulose nanocrystals (CNC), while fresh palm (FP) samples 36.17% of cellulose and 34.35% of CNC. The CNCs have higher crystallinity than the raw fibers and Zeta sizer was between 25 and 1150 nm. TGA analysis showed that DP demonstrated noticeable thermal resistance.

There is a great scientific curiosity to discover all environments sheltering microalgae, especially those with exceptional characteristics from coldest to hottest ones, the purpose remains to explore the potential of the native microalgae flora and the research for new bioactive compounds. This study aimed to isolate a polysaccharide-producing microalga from an extreme ecosystem and to evaluate its capacity to inhibit the α-d-glucosidase enzyme. Chlorella strain is isolated from hypersaline Lake in the Algerian desert. The exopolysaccharide extraction was performed by the concentration of free-cell supernatant in a rotary evaporator. The infrared analysis showed a characteristic footprint of carbohydrates with particular functional groups, such as sulfate. Gas chromatography–mass spectrometry has revealed a hetero-exopolysaccharide composed of galactose 35.75%, glucose 21.13%, xylose 16.81%, fructose 6.96%, arabinose 5.10%, and glucuronic acid 2.68%. The evaluation of the anti-hyperglycemic activity demonstrated a significant α-d-glucosidase inhibition of 80.94 ± 0.01% at 10 mg mL⁻¹ with IC₅₀ equal to 4.31 ± 0.20 mg mL⁻¹. This study opens a vast prospect to use exopolysaccharides as natural nutraceutical or food additive. Graphical Abstract

The scientific community continue to explore novel bioactive molecules by investigating natural origins; microalgae are photosynthetic organisms considered as a sustainable resource to use in many fields. They present a high diversity in species and richness in terms of attractive bio-compounds. The aim of this review is to (1) provide first an overview of current issues related to oxidative stress, and propose a natural metabolite derived from eukaryotic and prokaryotic microalgae; ‘polysaccharides’ as a powerful antioxidant agent, then, (2) organize the available data on the antioxidant potential of polysaccharides derived from the main microalgal groups (red microalgae, green microalgae, and cyanobacteria) and especially highlighted the key species of each group (Porphyridium sp., Chlorella sp., and Arthrospira sp., respectively), meanwhile, (3) we described the chemical composition of polysaccharides from each class, and (4) we cite briefly the most factors affecting the antioxidant activity of these molecules. Finally, we explored the major challenges and gaps found to require more investigation.

The anti-inflammatory and antihyperglycemic effects of polysaccharides extracted from Alhagi maurorum Medik. seeds, spontaneous shrub collected in Southern of Algerian Sahara were investigated. Their water extraction followed by alcoholic precipitation was conducted to obtain two water-soluble polysaccharides extracts (WSPAM1 and WSPAM2). They were characterized using Fourier transform infrared, ¹H/¹³C Nuclear Magnetic Resonance, Gas Chromatography-Mass Spectrometry and Size Exclusion Chromatography coupled with Multi-Angle Light Scattering. The capacity of those fractions to inhibit α-amylase activity and thermally induced Bovine Serum Albumin denaturation were also investigated. WSPAM1 and WSPAM2 were galactomannans with a mannose/galactose ratio of 2.2 and 2.4, respectively. The SEC-MALLS analysis revealed that WSPAM1 had a molecular weight of 1.4 × 10⁶ Da. The investigations highlighted antinflammatory and antihyperglycemic effects in a dose-dependant manner of WSPAM1 and WSPAM2.