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Anaerobic fermentation of carrageenan residues for the production of antifungal active compounds and their use to inhibit the growth of phytopathogenic bacteria is a novel approach to the utilization of carrageenan residues. In the present study, the treatment of carrageenan residue by anaerobic biofermentation technique showed strong growth inhibitory activity against Fusarium graminearum and Magnaporthe oryzae , which are the typical phytopathogens that reduce the crop yield, with MIC values of 0.0016% (v/v) and 0.00032% (v/v), respectively. The total concentration of polyphenols and flavonoids increased significantly to 20.41 μg/mL and 29.97 μg/mL after anaerobic fermentation. Amino acid metabolic pathway analysis showed that the substances and energy used by colonies to produce antifungal drugs are derived from amino acid metabolism, especially alanine and γ-aminobutyric acid (GABA). The results of redundancy analysis (RDA) indicated that anaerobic fermentation of carrageenan gum residues increased the abundance of specific bacterial groups included Bacillus, Komona, Caproiciproducens, Lactobacillus, Bovibacillus, and SN8, and that the increase in the number of these species favored the production of polyphenols and flavonoids with antifungal activity. This study provides a viable avenue for resource utilization of carrageenan residues. [Display omitted] • Anaerobic fermentation of carrageenan residues has antifungal activity. • Fermentation significantly increased total polyphenols and flavonoid contents. • Anaerobic fermentation of carrageenan residues increased the abundance of bacteria. • Increase of the species favored polyphenols and flavonoids with antifungal activity. • Carrageenan residues are potential materials for producing antifungal ingredients. [ABSTRACT FROM AUTHOR]

Polysaccharide extracted from red seaweed Bangia fusco-purpurea (BFP) is a novel sulfated galactan, differed from agarans and carrageenans in fine structure. In this study, in vitro fermentation characteristics of BFP by human gut microbiota and its protective effect on lipopolysaccharide (LPS)-induced injury in Caco-2 cells were investigated. Our results showed that BFP was mainly degraded at transverse colon for 18 h fermentation by gut microbiota with reduced molecular weight. Meanwhile, BFP fermentation was associated with increased short-chain fatty acids (SCFAs) as compared to control group, especially acetic acid was increased to 129.53 ± 0.24 from 82.14 ± 0.23 mmol/L, and butyric acid was up to 1.56 ± 0.004 from 0.62 ± 0.01 mmol/L. Furthermore, BFP promoted abundances of Bacteroidetes and Firmicutes , while decreased numbers of Proteobacteria. The up-regrated beneficial differential metabolites were SCFAs, L-proline, arginine, folic acid, pyridoxamine, thiamine, etc. (p < 0.05), and their related metabolic pathways mainly included mTOR, arginine biosynthesis, and vitamin metabolism. Notably, BFP fermentation products at transverse colon significantly restored cell viability of LPS-treated Caco-2 cells from 73.79 ± 0.48 % to 93.79–99.64 %, which might be caused by increased beneficial differential metabolites (e.g. , SCFAs). Our findings suggest that BFP has prebiotic potential and can enhance gut health. • In vitro gut fermentation of Bangia fusco-purpurea polysaccharide (BFP) was explored. • BFP was mainly degraded at transverse colon by gut microbiota. • BFP significantly altered the composition and diversity of gut microbiota. • BFP significantly enhanced the production of SCFAs and beneficial metabolites. • Fermented products of BFP attenuated LPS-induced injury in Caco-2 cells. [ABSTRACT FROM AUTHOR]