Production and viscosity of Xanthan Gum are increased by LED irradiation of X. campestris cultivated in medium containing produced water of the oil industry

Effect of photostimulation through red LED light radiation on natural fermentation of table olives: An innovative case study with Negrinha the Freixo variety

In this study, for the first time, red LED light radiation was applied to the fermentation process of table olives using the Negrinha de Freixo variety. Photostimulation using LED light emission (630 ± 10 nm) is proposed to shorten and speed up this stage and reduce time to market. Several physical-chemical characteristics and microorganisms (total microbial count of mesophilic aerobic, molds, yeasts, and lactic acid bacteria) and their sequence during fermentation were monitored. The fermentation occurred for 122 days, with two irradiation periods for red LED light. The nutritional composition and sensory analysis were performed at the end of the process. Fermentation under red LED light increased the viable yeast and lactic acid bacteria (LAB) cell counts and decreased the total phenolics in olives. Even though significant differences were observed in some color parameters, the hue values were of the same order of magnitude and similar for both samples. Furthermore, the red LED light did not play a relevant change in the texture profile, preventing the softening of the fruit pulp. Similarly, LED light did not modify the existing type of microflora but increased species abundance, resulting in desirable properties and activities. The species identified were yeasts - Candida boidinii, Pichia membranifaciens, and Saccharomyces cerevisiae, and bacteria - Lactobacillus plantarum and Leuconostoc mesenteroides, being the fermentative process dominated by S. cerevisiae and L. plantarum. At the end of fermentation (122 days), the irradiated olives showed less bitterness and acidity, higher hardness, and lower negative sensory attributes than non-irradiated. Thus, the results of this study indicate that red LED light application can be an innovative technology for table olives production.

Photodynamic inactivation of Staphylococcus aureus by ecological antibacterial solutions associating LED (ʎ 450 ± 10 nm) with curcumin and olive leaf extracts

Antimicrobial resistance is a problem in contemporary society, with Staphylococcus aureus standing out as a threat due to its ability to colonize, its pathogenicity, and its expression of several virulence factors. In this context, antimicrobial photodynamic inactivation (aPDI) emerges as an alternative to conventional microbicidal or microbiostatic systems, enabling numerous and successive applications without developing side effects and microbial resistance. In this context, an aPDI system against cultures of S. aureus based on a water-in-oil (W/O) emulsion incorporating curcumin as the photosensitizer (PS), with and without olive leaf extract (OLE), was developed and the antibacterial efficacy evaluated under LED activation (ʎ450 ± 10 nm) by depositing an energy density of 14 J/cm². The produced emulsified systems showed no significant differences in the droplet size and morphology, remaining stable along the tested period of 30 days. The bacterial reduction achieved after the first aPDI application for the emulsions added with curcumin and curcumin combined with the OLE was 5 log10 CFU.mL^-1 and 6 log10 CFU.mL^-1, respectively, revealing a significant difference between the two groups (p < 0.0001). After the second aPDI application, an increased microbial reduction (7 log10 CFU.mL^-1) was observed for both studied groups even with a low significant difference (p < 0.05). The PS loading through an emulsified system for aPDI obtained a bactericidal action against S. aureus, increased by applying two aPDI, showing a significant synergy between photodynamic inactivation, OLE delivery and antibacterial activity. In addition, the developed solutions were produced using natural products by an ecologically correct process.

Prospects of Biogenic Xanthan and Gellan in Removal of Heavy Metals from Contaminated Waters

Biosorption is considered an effective technique for the treatment of heavy-metal-bearing wastewaters. In recent years, various biogenic products, including native and functionalized biopolymers, have been successfully employed in technologies aiming for the environmentally sustainable immobilization and removal of heavy metals at contaminated sites, including two commercially available heteropolysaccharides-xanthan and gellan. As biodegradable and non-toxic fermentation products, xanthan and gellan have been successfully tested in various remediation techniques. Here, to highlight their prospects as green adsorbents for water decontamination, we have reviewed their biosynthesis machinery and chemical properties that are linked to their sorptive interactions, as well as their actual performance in the remediation of heavy metal contaminated waters. Their sorptive performance in native and modified forms is promising; thus, both xanthan and gellan are emerging as new green-based materials for the cost-effective and efficient remediation of heavy metal-contaminated waters.