Light Irradiation Coupled with Exogenous Metal Ions to Enhance Exopolysaccharide Synthesis from Agaricus sinodeliciosus ZJU-TP-08 in Liquid Fermentation

To promote Agaricus sinodeliciosus var. Chaidam ZJU-TP-08 growth and metabolites accumulation, a novel integrated strategy was developed by adopting high levels of metal ions coupled with light treatment. The results revealed that yellow and blue light could significantly promote biomass and exopolysaccharides production, respectively. Furthermore, the yellow–blue light shift strategy could stimulate exopolysaccharides formation. Ca2+ ions coupled with blue light mostly promoted exopolysaccharides production related to oxidative stress, which was 42.00% and 58.26% higher than that of Ca2+ ions coupled with the non-light and dark cultivation without Ca2+ ions in 5-L bioreactor. RNA-seq was performed to uncover the underlined molecular mechanism regulated by light-induced gene expressions in exopolysaccharides biosynthesis and oxidative stress. The findings of this work provide valuable insights into adopting metal ions coupled with the light-assisted method for the macrofungus submerged fermentation for exopolysaccharides production.

Gibberellic Acids Promotes Growth and Exopolysaccharides Production in Tetraselmis Suecica Under Reciprocal Nitrogen Concentration: An Assessment on Antioxidant Properties and Nutrients Removal Efficacy of Immobilized Iron-magnetic Nanoparticles

The present study was aimed to assess the effect of gibberellic acids to enhance the growth, biomass, pigment, and exopolysaccharides production in Tetraselmis suecica under reciprocal nitrogen concentrations. For this study, the seven types of experimental media (N-P, NL-P/2GA3, N0-P/2GA3, NL-P/4GA3, N0-P/4GA3, NL-P/6GA3, N0-P/6GA3) were prepared include the addition of gibberellic acids under various nitrogen concentrations. The experiment was lasted for 15 days and the cell density, biomass, chlorophyll ‘a’, and exopolysaccharides (EPS) concentration of T. suecica were estimated for every three days. Then the EPS was subjected to the analyses of chemical (carbohydrate, protein, sulfate, and uronic acid), and antioxidant activity. In addition nutrient removal efficiency was evaluated by using different concentration of EPS. The highest DPPH (86.7±0.95 %) and hydroxyl radical activity (85.7±2.48 %) were observed in 2.5 and 1.2 mg/mL of EPS concentration. The immobilized magnetic Fe3O4-EPS nanoparticles (5.0 and 10.0 g/L) have efficiently removed the excessive phosphate (89.5±1.65 %) and nitrate (73.5±1.72 %) from the Litopenaeus vannamei cultured wastewater. Thus, applying gibberellic acids combined with limited nitrogen concentration could produce higher EPS that could exhibit excellent antioxidant activity, and nutrient removal efficacy in the form of Fe3O4-EPS magnetic nanoparticles.

Compounds with Distinct Targets Present Diverse Antimicrobial and Antibiofilm Efficacy against Candida albicans and Streptococcus mutans, and Combinations of Compounds Potentiate Their Effect

Candida albicans and Streptococcus mutans interact synergistically in biofilms associated with a severe form of dental caries. Their synergism is driven by dietary sucrose. Thus, it is necessary to devise strategies to hinder the development of those biofilms and prevent cavities. Six compounds [tt-farnesol (sesquiterpene alcohol that decreases the bacterium acidogenicity and aciduricity and a quorum sensing fungal molecule), myricetin (flavonoid that interferes with S. mutans exopolysaccharides production), two 2’-hydroxychalcones and 4’-hydroxychalcone (intermediate metabolites for flavonoids), compound 1771 (inhibitor of lipoteichoic synthase in Gram-positive bacteria)] with targets in both fungus and bacterium and their products were investigated for their antimicrobial and antibiofilm activities against single-species cultures. The compounds and concentrations effective on single-species biofilms were tested alone and combined with or without fluoride to control initial and pre-formed dual-species biofilms. All the selected treatments eliminated both species on initial biofilms. In contrast, some combinations eliminated the bacterium and others the fungus in pre-formed biofilms. The combinations 4’-hydroxychalcone+tt-farnesol+myricetin, 4’-hydroxychalcone+tt-farnesol+fluoride, and all compounds together with fluoride were effective against both species in pre-formed biofilms. Therefore, combinations of compounds with distinct targets can prevent C. albicans and S. mutans dual-species biofilm build-up in vitro.

Technological Characterization of Lactic Acid Bacteria Isolated from Different Sheep’s Milk

Background: Technological characterization of lactic acid bacteria isolated from sheep’s milk collected in 3 regions in northwestern Algeria.Methods: During the period from 2018 to 2019, fifty strains of Lactic acid bacteria isolated from samples sheep’s milk were evaluated for several technologically-relevant properties: diacetyl and exopolysaccharides production, acidification, proteolytic and lipolytic activity and their antagonist activity against Escherichia coli and Pseudomonas aeruginosa. Result: The results indicate that among all the isolates only 20% were distinguished by their production of EPS mainly the genus Leuconostoc. Diacetyl production was observed in 71% of Lactobacillus, 60% of Enterococcus and 25% in Leuconostoc. 94% isolates showed moderate proteolytic activity. 56% and 60% of the strains degraded tween 80 and olive oil respectively for lipolytic activity. Inhibition activity by the cultures LAB was about 82% and 78% against E. coli and P. aeruginosa respectively. No culture supernatants inhibit P. aeruginosa, however 18% of the Enterococcus trains inhibit E. coli. BME1.A2 and BME2.D4 showed their highest acidification capacity developing a very large quantity of lactic acid after 24 h of incubation, i.e., 7.6 and 8.4 g lactic acid/L respectively.

Medium optimization for exopolysaccharides production by Bacillus Zhangzhouensis BZ 16 strain isolated from Khnifiss Lagoon

The increased demand for natural polymers for diverse industrial applications in last years has led to a renovated interest in exopolysaccharides (EPS) production by microorganisms. Ecological roles of EPS especially for those isolated from extreme habitats such as hypersaline ponds have been reported in several studies. A moderate halophilic strain producing exopolysaccharide (EPS) has been isolated earlier. However, the EPS production of the strain (2 g/L) was relatively low to exploit it at the industrial level. In the present work, the strain was identified as Bacillus zhangzhouensis and named as BZ 16 and the optimal medium was studied to boost the EPS production. Maximum EPS production was obtained in medium with 125 g/L sucrose, 30 g/L yeast extract. Phosphate source inhibited EPS production even if it increased the growth. Under optimal medium composition, EPS was produced at 12.37 g/L, which was 6 times greater than the production yield achievable without optimizing conditions.