The optimum conditions and mechanism for increasing exo-polysaccharide production of Truffles melanosporum by Dioscorea saponins

High-Molecular-Weight Exopolysaccharides Production from Tuber brochii Cultivated by Submerged Fermentation

Truffles are known worldwide for their peculiar taste, aroma, and nutritious properties, which increase their economic value. However, due to the challenges associated with the natural cultivation of truffles, including cost and time, submerged fermentation has turned out to be a potential alternative. Therefore, in the current study, the cultivation of Tuber borchii in submerged fermentation was executed to enhance the production of mycelial biomass, exopolysaccharides (EPSs), and intracellular polysaccharides (IPSs). The mycelial growth and EPS and IPS production was greatly impacted by the choice and concentration of the screened carbon and nitrogen sources. The results showed that sucrose (80 g/L) and yeast extract (20 g/L) yielded maximum mycelial biomass (5.38 ± 0.01 g/L), EPS (0.70 ± 0.02 g/L), and IPS (1.76 ± 0.01 g/L). The time course analysis of truffle growth revealed that the highest growth and EPS and IPS production was observed on the 28th day of the submerged fermentation. Molecular weight analysis performed by the gel permeation chromatography method revealed a high proportion of high-molecular-weight EPS when 20 g/L yeast extract was used as media and the NaOH extraction step was carried out. Moreover, structural analysis of the EPS using Fourier-transform infrared spectroscopy (FTIR) confirmed that the EPS was β-(1-3)-glucan, which is known for its biomedical properties, including anti-cancer and anti-microbial activities. To the best of our knowledge, this study represents the first FTIR analysis for the structural characterization of β-(1-3)-glucan (EPS) produced from Tuber borchii grown in submerged fermentation.

Optimization of the nutritional constituents for ergosterol peroxide production by Paecilomyces cicadae based on the uniform design and mathematical model

we optimized medium components for the production of ergosterol peroxide (EP) by Paecilomyces cicadae based on a mono-factor experiment, a uniform design, and a non-linear regression analysis. The maximum EP yield achieved was 256 μg/L, which was increased by 5 folds compared with that before the optimization. Structured Monod model, Andrews model, Contois model, and Aibe model were developed to describe the effects of viscosity inhibition, substrate, and production on biomass growth. The results showed that the Monod model could predict biomass growth, and the effects of viscosity and substrate on the EP concentration were significantly higher compared with the effect of production. The addition of water and glycerol could decrease the viscosity inhibition and glycerol inhibition, and further increase the EP yield. The newly developed structured model was demonstrated for batch growth of P.cicadae.

Pilot-scale production of exopolysaccharide from Leuconostoc pseudomesenteroides XG5 and its application in set yogurt

Exopolysaccharide from Leuconostoc pseudomesenteroides XG5 (XG5 EPS) is a linear dextran that is built by glucose units via α-1,6 glycosidic bond. The primary objective of this study was to investigate the yield of XG5 EPS and its application in set yogurt. In laboratory scale, the culture conditions of XG5 EPS production were optimized using the L9 (3³) orthogonal test. Here, the optimized yield of XG5 EPS was 26.02 g/L under the conditions of 100 g/L sucrose, initial pH 7.0, 25°C incubation, and 100 rpm for 36 h in a shaking flask. Based on the optimized parameters of laboratory scale, a pilot fed-batch fermentation was performed in a 50-L bioreactor with an adjusted agitation speed of 20 rpm. The XG5 EPS yield reached 40.07 g/L in fed-batch fermentation, which was 54% higher than that achieved in laboratory scale. In addition, XG5 EPS was added into set yogurt to investigate its effect on the stability of set yogurt. Our data demonstrated that the XG5 EPS improved the water-holding capacity, texture profile, and viscosity of set yogurt during cold storage compared with the controls. In particular, addition of 0.5% XG5 EPS increased the structure of 3-dimensional network of set yogurt, which eventually improved the physical stability of the set yogurt. Overall, this study provided new insights for exploring the pilot scale production and application of dextran.

Increased Extracellular Saponin Production after the Addition of Rutin in Truffle Liquid Fermentation and Its Antioxidant Activities

Saponins possess a variety of pharmacological effects and exhibit great potential in the food industry as bioactive substances. In this study, extracellular saponin production via the liquid fermentation of Tuber melanosporum occurred with the addition of rutin. For this purpose, medium composition and culture conditions were optimized using single-factor experiments and an orthogonal experiment design. The optimal medium consisted of glucose (43.5 g/L), peptone (6 g/L), KH2PO4 (1.15 g/L), NaCl (0.2 g/L), vitamin B2 (0.082 g/L), vitamin B6 (0.1 g/L), vitamin C (0.02 g/L), and rutin (4.8 g/L). The culture conditions were as follows: 12.5% (v/v) inoculation, medium volume of 50 mL/250 mL flask, culture temperature of 24 °C, shaker speed of 190 rpm, initial pH of 5.7, and culture time of 96 h. Finally, a maximal extracellular saponin content of 0.413 g/L was obtained, which was 134.7% higher than that in the base medium. Rutin proved to be an excellent promoter, because the saponin production was increased by 50.2% compared to that in the optimized medium without rutin. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity, hydroxyl radical scavenging activity, and ferric reducing antioxidant power of truffle saponins reached 94.13%, 79.26%, and 42.22 mM, respectively. This study provides a useful strategy for fungal bioactive saponin production by liquid fermentation with the addition of flavonoid compounds.