Selenium nanoparticles (SeNPs) have attracted considerable interest due to their unique physicochemical properties, low toxicity compared with inorganic selenium (Se) compounds, and diverse biological activities. Microorganisms, particularly species of the genus Bacillus, represent efficient biological platforms for SeNP synthesis because of their tolerance to selenium oxyanions and their ability to reduce selenite Se (IV) to elemental selenium (Se0) under mild conditions. Selenate-reduction is relatively poorly understood in this genus, so the candidate selenate-reductase system proposed here is inferred from selenium-respiring organisms and has not been genetically confirmed in Bacillus. This review summarizes current knowledge on Bacillus-mediated SeNP biosynthesis with an emphasis on microbial selenium transformation, cellular responses, and biochemical processes involved in nanoparticle formation. The roles of redox-associated pathways, reducing equivalents, candidate enzymes, metabolites, and extracellular biomolecules in selenium reduction, nucleation, and stabilization are critically discussed, while highlighting the limitations of current mechanistic understanding and the need for further genetic validation. In addition, this review examines how bacterial strain characteristics and cultivation conditions influence SeNP properties, including particle size, surface chemistry, stability, and biological activity. The applications of Bacillus-derived SeNPs, including antimicrobial, antioxidant, anticancer, agricultural, and environmental applications, are discussed in relation to the nanoparticle characteristics and biological performance. Throughout the review, evidence is explicitly attributed to the relevant source system, distinguishing among Bacillus-derived, other microbial, chemically synthesized, plant-derived, and general SeNP literature. Current biomedical evidence for Bacillus-mediated SeNPs is based predominantly on in-vitro studies. Finally, emerging approaches for improving microbial SeNP production through strain selection, metabolic engineering, and process optimization are highlighted. This review provides an integrated perspective on Bacillus-mediated SeNP biosynthesis, identifies future research directions and offers insights for researchers in microbiology, bioprocess engineering, animal nutrition and agricultural biotechnology.
This study optimized fermentation conditions for producing a oyster (Crassostrea gigas) fermentation broth using Aspergillus niger. Based on 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH) radical-scavenging activity, single-factor tests and response surface methodology identified optimal conditions of 28℃, 48 h fermentation time, 70
Cobalt stress can promote the accumulation of dendrobine-type total alkaloids (DTTAs) in Trichoderma longibrachiatum UN32; however, the signalling mechanisms underlying this response remain unclear. In this study, we examined whether changes in Ca2+ and nitric oxide (NO) signalling were associated with ROS-related responses and cobalt-enhanced DTTAs production under cobalt stress. Co2+ treatment increased DTTAs accumulation together with intracellular hydrogen peroxide (H2O2), Ca2+ and NO levels. Among Ca2+ signalling inhibitors, neomycin (Neo) showed the strongest effect: 6 mM Neo reduced intracellular Ca2+ by 59.86%, DTTAs production by 33.70% and H2O2 levels by 25.50% compared with CoCl2 treatment. Time-course analysis further showed coordinated changes in H2O2, Ca2+ and DTTAs accumulation during fermentation. In contrast, L-NAME-mediated inhibition of NO synthesis did not significantly affect DTTAs production. These findings suggest that ROS-Ca2+ interplay is associated with cobalt-enhanced DTTAs accumulation in T. longibrachiatum UN32, whereas NO has a limited role under the tested conditions.
The increasing demand for natural nutraceuticals has driven interest in marine resources like sea cucumbers (Stichopus japonicus), which are rich in proteins that can be biotransformed into bioactive compounds. This study investigated the bioconversion of Stichopus japonicus through fermentation with Lactobacillus plantarum to enhance its bioactive profile. Fermentation significantly altered the proximate composition, increasing protein content (51.25% dry basis) while reducing moisture, fiber, ash, and organic matter. The degree of hydrolysis reached 70.76%, resulting in elevated levels of free amino acids, bioactive peptides, and gamma-aminobutyric acid (GABA), which increased 2-3 fold across all molecular weight fractions. Bioactivity assays revealed potent antioxidant (IC50 as low as 0.97 mg/mL), anti-inflammatory (IC50 down to 1.11 mg/mL), and antidiabetic (IC50 as low as 1.04 mg/mL) activities, with the < 3 kDa fraction consistently showing the highest potency. LC-HRMS analysis identified 25 novel peptides, all predicted as non-toxic, with several demonstrating high bioactivity potential. These results demonstrate that fermentation with Lactobacillus plantarum effectively valorizes Stichopus japonicus into a multi-functional ingredient enriched with protein, GABA, and bioactive peptides, offering promising applications in functional foods and nutraceuticals.
Immunocompromised patients, especially hematopoietic stem cell transplants (HSCT) / bone marrow transplant recipients, are at risk for colonization and infection with carbapenem-resistant Klebsiella pneumoniae (CR-KP) which is associated with increased bloodstream infections and mortality in this population. In this susceptible population, we investigated the molecular epidemiology of CR-KP. The strains isolated over a five-year period (2017-2021) were then characterized by PCR and sequencing targeting carbapenemase genes. ERIC-PCR was utilized to examine clonal relations, while multilocus sequence typing was carried out on representative isolates. Analysis of 142 CR-KP uncovered remarkable genetic heterogeneity with six predominant clusters making up for 83,8% of strains and one major cluster. Novel findings in K. pneumoniae included: undescribed MLST profile ST5187, emergence of bla VIM-1 in ST397, emergence of bla OXA-48-like in ST219, co-carriage of either bla NDM-1 + bla OXA-48-like in ST15 or bla VIM-like + bla NDM-1 in ST405. CR-KP, brought to light new carbapenemase gene associations and undescribed MLST profiles. To prevent transmission of high-risk clones in immunocompromised populations, enhanced molecular surveillance and robust infection control are of high importance.
