Microencapsulation via Spray-Drying of Geraniol-Loaded Emulsions Stabilized by Marine Exopolysaccharide for Enhanced Antimicrobial Activity

This work was supported by the Ministry of Higher Education and Scientific Research, Tunisia, through the scholarship program under the project” Mobility to Encourage Young Tunisian Researchers” (No. 19PEJC07-02, 2019).The current study investigates the formation of microencapsulated geraniol powder, with the exopolysaccharide EPS-K1B3 produced by Halomonas caseinilytica K1, as wall material, using spray-drying. Evaluation of the antimicrobial activity of the functional emulsions, prepared at either pH 5 or pH 7, was carried out against Gram-positive (Listeria innocua (ATCC 33090)) and Gram-negative (Escherichia coli (DSM682)) bacterial strains. Results showed prolonged antimicrobial efficacy until 30 days of incubation for geraniol microcapsules compared to wet geraniol emulsions, which could confirm the ability of the spray-drying process to protect encapsulated geraniol for a longer period. The highest antimicrobial efficacy of geraniol microcapsules was observed against L. innocua at pH 5. Therefore, the influence of pH on the functional property of geraniol microcapsules could be highlighted beside the targeted bacterial strain.publishersversionpublishe

Isolation and characterization of a mesophilic heavy-metals-tolerant sulfate-reducing bacterium Desulfomicrobium sp. from an enrichment culture using phosphogypsum as a sulfate source

A sulfate-reducing bacterium, was isolated from a 6 month trained enrichment culture in an anaerobic media containing phosphogypsum as a sulfate source, and, designated strain SA2. Cells of strain SA2 were rod-shaped, did not form spores and stained Gram-negative. Phylogenetic analysis of the 16S rRNA gene sequence of the isolate revealed that it was related to members of the genus Desulfomicrobium (average sequence similarity of 98%) with Desulfomicrobium baculatum being the most closely related (sequence similarity of 99%). Strain SA2 used thiosulfate, sulfate, sulfite and elemental sulfur as electron acceptors and produced sulfide. Strain SA2 reduced sulfate contained in 1–20 g/L phosphogypsum to sulfide with reduction of sulfate contained in 2 g/L phosphogypsum being the optimum concentration. Strain SA2 grew with metalloid, halogenated and non-metal ions present in phosphogypsum and with added high concentrations of heavy metals (125 ppm Zn and 100 ppm Ni, W, Li and Al). The relative order for the inhibitory metal concentrations, based on the IC50 values, was Cu, Te > Cd > Fe, Co, Mn > F, Se > Ni, Al, Li > Zn

Microencapsulation of Natural Food Antimicrobials: Methods and Applications

The global demand for safe and healthy food with minimal synthetic preservatives is continuously increasing. Some natural food antimicrobials with strong antimicrobial activity and low toxicity have been considered as alternatives for current commercial food preservatives. Nonetheless, these natural food antimicrobials are hardly applied directly to food products due to issues such as food flavor or bioavailability. Recent advances in microencapsulation technology have the potential to provide stable systems for these natural antibacterials, which can then be used directly in food matrices. In this review, we focus on the application of encapsulated natural antimicrobial agents, such as essential oils, plant extracts, bacteriocins, etc., as potential food preservatives to extend the shelf-life of food products. The advantages and drawbacks of the mainly used encapsulation methods, such as molecular inclusion, spray drying, coacervation, emulsification, supercritical antisolvent precipitation and liposome and alginate microbeads, are discussed. Meanwhile, the main current applications of encapsulated antimicrobials in various food products, such as meat, dairy and cereal products for controlling microbial growth, are presented

A comparative study of the biodegradability of oleic acid by sludge from a reactor fed with olive mill wastewater and sludge from a reactor fed with oleic acid

In the present study, we investigate the biodegradability of oleic acid by sludge from anaerobic filter reactor fed with olive mill wastewater (sludge T). A comparative study was conducted using a second sludge from an expanded granular bed reactor exposed to oleic acid (sludge P). The performance of treating oleic acid and the influence of the composition of the culture media were investigated and compared. Methane production by sludge T started after a lag phase of 150 hours. However no lag phase was observed with sludge P. In contrast a higher methane production was obtained with the sludge T. The addition of nutrients (minerals and yeast extract) to culture medium reduced the lag phase of methane production by 40 hours

Isolement et caractérisation de bactéries d’intérêts associées aux vinaigres traditionnels Tunisiens

International audienc

Production and structural characterization of exopolysaccharides from newly isolated probiotic lactic acid bacteria

In this work, four exopolysaccharide-producing lactic acid bacteria (LAB) strains, newly isolated fromTunisian spontaneously fermented foods and beverages, namely bovine and turkey meat sausages(BMS and TMS), date palm sap (DPS) and cow milk (CM), were identified as Leuconostoc citreum-BMS,Leuconostoc mesenteroides-TMS, Pediococcus pentosaceus-DPS and Leuconostoc pseudomesenteroides-CM,respectively. The isolated strains showed the ability to withstand simulated human gastrointestinal (GI)tract conditions (low pH, lysozyme, bile salts, pepsin and pancreatin) and showed high surface hydropho-bicity (79–90%), besides their ability to act against Escherichia coli and Listeria monocytogenes and toproduce exopolysaccharides (EPS). Therefore, these isolates can be served as potential probiotics. The pro-duced EPS were growth-associated suggesting that they are primary metabolites. The molecular weightswere higher than 106Da using HPLC-SEC. 2D-NMR results indicated that all the samples were mixtures ofdextran and levan, except for EPS-CM which was a levan-type EPS. Furthermore, the EPS samples showedan abitlity to inhibit and to disrupt pathogenic biofilms and showed high thermostability studied via dif-ferential scanning calorimetry (DSC) with melting points higher than 224◦C making them promising tobe used in thermal processed foods

Potential biotechnological properties of an exopolysaccharide produced by newly isolated Bacillus tequilensis-GM from spontaneously fermented goat milk

In the present work, an exopolysaccharide (EPS) was produced by a newly isolated Bacillus tequilensis-GM ropy strain. Results showed that EPS-GM was produced simultaneously with the growth phase and reached its maximum (2.9 g/L) when sucrose was used as carbon source. According to GC-MS and HPLC-SEC results, the recovered EPS-GM was composed by fructose, glucose, mannose, galactose, galactosamine and N-acetyl-glucosamine, with high molecular weight ranging between 1.8 and 2.5×106 Da. Different properties of EPS-GM were tested. Results showed that crude EPS-GM has several potential features, including high thermostability evaluated by DSC (with a melting point of 222 °C), good emulsifying properties and stability at both neutral and acidic pH, and high capacities to adsorb heavy metal ions (94.96% of Fe2+, 97.66% of Zn2+ and 98.24% of Cu2+) making it promising to be used in different industrial fields