This study aimed at the production of marine bacterial exopolysaccharides (EPS) as biodegradable and nontoxic biopolymers, competing the synthetic derivatives, with detailed structural and conformational analyses using spectroscopy techniques. Twelve marine bacterial bacilli were isolated from the seawater of Mediterranean Sea, Egypt, then screened for EPS production. The most potent isolate was identified genetically as Bacillus paralicheniformis ND2 by16S rRNA gene sequence of ~99 % similarity. Plackett-Burman (PB) design identified the optimization conditions of EPS production, which yielded the maximum EPS (14.57 g L-1) with 1.26-fold increase when compared to the basal conditions. Two purified EPSs namely NRF1 and NRF2 with average molecular weights (Mw¯) of 15.98 and 9.70 kDa, respectively, were obtained and subjected for subsequent analyses. FTIR and UV-Vis reflected their purity and high carbohydrate contents while EDX emphasized their neutral type. NMR identified the EPSs as levan-type fructan composed of β-(2-6)-glycosidic linkage as a main backbone, and HPLC explained that the EPSs composed of fructose. Circular dichroism (CD) suggested that NRF1 and NRF2 had identical structuration with a little variation from the EPS-NR. The EPS-NR showed antibacterial activity with the maximum inhibition against S. aureus ATCC 25923. Furthermore, all the EPSs revealed a proinflammatory action through dose-dependent increment of expression of proinflammatory cytokine mRNAs, IL-6, IL-1β and TNFα.
exopolysaccharides, circular dichroism, antibacterial, Bacillus paralicheniformis, Plackett-Burman, proinflammatory
NCBI PubMed ID: 37028872Publication DOI: 10.1016/j.carbpol.2023.120743Journal NLM ID: 8307156Publisher: Elsevier
Correspondence: K. Matsuo
; M.I.A. Ibrahim
Institutions: Department of Botany and Microbiology, Faculty of Science, Kafrelsheikh University, Kafr El Sheikh 33516, Egypt, National Institute of Oceanography and Fisheries (NIOF), Egyp, Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima 739-8521, Japan, CNRS, LCPM, F-54000, Université de Lorraine, Nancy 54001, France, Program of Biomedical Science, Graduate School of Integrated Sciences for Life, Hiroshima University, Hiroshima 739-8521, Japan, Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan
Methods: 13C NMR, 1H NMR, NMR-2D, DNA techniques, conformation analysis, FTIR, composition analysis, HPLC, HPSEC, CD, antibacterial assay, SEM, EDX, UV–vis
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