Enhanced production of exopolysaccharides using industrial grade starch as sole carbon source

Biosynthesis of exopolysaccharide from waste molasses using Pantoea sp. BCCS 001 GH: a kinetic and optimization study

The bacterium Pantoea sp. BCCS 001 GH produces an exopolysaccharide (EPS) named Pantoan through using sugar beet molasses (SBM) as an inexpensive and widely available carbon source. This study aims to investigate the kinetics and optimization of the Pantoan biosynthesis using Pantoea sp. BCCS 001 GH in submerged culture. During kinetics studies, the logistic model and Luedeking-Piret equation are precisely fit with the obtained experimental data. The response surface methodology (RSM)-central composite design (CCD) method is applied to evaluate the effects of four factors (SBM, peptone, Na2HPO4, and Triton X-100) on the concentration of Pantoan in batch culture of Pantoea sp. BCCS 001 GH. The experimental and predicted maximum Pantoan production yields are found 9.9 ± 0.5 and 10.30 g/L, respectively, and the best prediction factor concentrations are achieved at 31.5 g/L SBM, 2.73 g/L peptone, 3 g/L Na2HPO4, and 0.32 g/L Triton X-100 after 48 h of submerged culture fermentation, at 30 °C. The functional groups and major monosaccharides (glucose and galactose) of a purified Pantoan are described and confirmed by 1HNMR and FTIR. The produced Pantoan is also characterized by thermogravimetric analysis and the rheological properties of the biopolymer are investigated. The present work guides the design and optimization of the Pantoea sp. BCCS 001 GH culture media, to be fine-tuned and applied to invaluable EPS, which can be applicable in food and biotechnology applications.

Transcriptomic, Biochemical, and Morphological Study Reveals the Mechanism of Inhibition of Pseudopestalotiopsis camelliae-sinensis by Phenazine-1-Carboxylic Acid

Gray blight disease is one of the most destructive diseases of tea plants and occurs widely in the tea-growing areas of the world. It is caused by several fungal phytopathogens, of which Pseudopestalotiopsis camelliae-sinensis is the main pathogen in China. The environmentally friendly antimicrobial, phenazine-1-carboxylic acid (PCA), a metabolite of the natural soil-borne bacteria Pseudomonas spp., can inhibit a range of fungal crop diseases. In this study, we determined that PCA was active against Ps. camelliae-sinensis in vitro. We studied the mode of action of PCA on hyphae using a microscopic investigation, transcriptomics, biochemical methods, and molecular docking. The results of scanning and transmission electron microscopy indicated that PCA caused developmental deformity of mycelia and organelle damage, and it significantly decreased the accumulation of exopolysaccharides on the hyphal surface. The transcriptome revealed that 1705 and 1683 differentially expressed genes of Ps. camelliae-sinensis treated with PCA were up-regulated or down-regulated, respectively, with genes associated with ribosome biogenesis, oxidative phosphorylation, and encoding various proteins of N-glycan biosynthesis being significantly up-regulated. Up-regulation of nine genes related to N-glycan biosynthesis of Ps. camelliae-sinensis in response to PCA treatment was confirmed by reverse transcription qPCR. The enzymatic activity of catalase and superoxide dismutase of hyphae was significantly decreased by PCA treatment. Our results indicated that exposure to PCA resulted in expression changes in oxidoreductase genes, accumulation of reactive oxygen species, and decreased activity of catalase, with concomitant damage to the fungal cell membrane and cell wall.

Antioxidant activity changes of exopolysaccharides with different carbon sources from Lactobacillus plantarum LPC-1 and its metabolomic analysis

The effects of different carbon sources on the antioxidant activity changes of exopolysaccharides (EPSs) were determined for the strains Lactobacillus plantarum LPC-1 with glucose, sucrose and its mixture as carbon sources, respectively. Meanwhile, GC-MS datasets coupled with multivariate statistical methods were used to investigate metabolic changes of EPSs-producing L. plantarum cultured with different carbon source. Among carbon sources examined, both of glucose and sucrose were favorable for the cell growth, while the maximum EPSs yield was achieved when sucrose was employed. EPSs cultured with different carbon sources showed remarkable different antioxidant activities, and EPSs with sucrose or mixed sugar as carbon source exhibited a promising antioxidant activity, such as hydroxyl scavenging activity and DPPH radical scavenging activity. Results from rice cultivation showed a similar conclusion that there were also significant differences in the antioxidant activities of EPSs obtained from different carbon sources in inducing rice resistance to chromium stress, but addition of EPSs had no significant impact on the uptake of Cr metals. Principal component analysis showed clear differences in metabolites among different treatment, and the glycolysis and tricarboxylic acid cycle were decreased when sucrose or mixed sugar was used as carbon source, and the production of lactic acid was also reduced, which might be the main reasons for the overproduction of EPSs. Our results indicated that Lactobacillus strain, depending on the carbon source in the medium, could produce EPSs of different biological properties, and the metabolomic analysis findings provided the first omics view of cell growth and EPSs synthesis in L. plantarum, which would be a theoretical basis for further improving the production of EPSs.