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Polar microorganisms produce physiologically active substances to adapt to harsh environments, and these substances can be used as biomedical compounds. The green microalga Micractinium variabile KSF0031, which was isolated from Antarctica, produced phytol, a natural antimicrobial agent. Furthermore, several polyunsaturated fatty acids (PUFAs), including omega-3, exhibit antioxidant properties. Here statistical methods (Plackett-Burman design and Box-Behnken design) were used to optimize the culture medium of KSF0031 to improve biomass production, and K2HPO4, MgSO4·7H2O, and ammonium ferric citrate green (AFCg) were selected as significant components of the culture medium. Changes in the concentration of K2HPO4 and MgSO4·7H2O as positive factors and AFCg as a negative factor affected cell growth to a remarkable degree. The biomass production in a 100 L culture using the optimized medium for 24 d at 18°C was improved by 37.5% compared to that obtained using the original BG-11 medium. The quantities of PUFAs and phytol obtained were 13 mg g-1 dry cell weight (DCW) and 10.98 mg g-1 DCW, which represent improved yields of 11.70% and 48.78%, respectively. The results of this study could contribute to an improved production of phytol and fatty acids from Antarctic microalgae in the biomedical industry. [ABSTRACT FROM AUTHOR]

Abstract Bacteria play an important role in preventing algal blooms and reducing their harm to the environment. To improve the algicidal activity of Pseudoalteromonas SP48 which had an inhibition effect on dinoflagellate Alexandrium tamarense, its growth medium and fermentation conditions were optimized for this bacterium. In this study, we used two steps to establish the optimum conditions. First, the proper proportion of medium was selected based on an orthogonal design. Then, the fermentation conditions were further optimized through uniform design in an enlarged 5L bioreactor. To test the algicidal ability of Pseudoalteromonas SP48 under the optimum conditions, algal cell morphology was observed by transmission electron microscopy (TEM). After the orthogonal design, we found that the optimum medium was [0.7% (m/v) tryptone, 0.2% (m/v) soluble starch, 0.2% (m/v) sucrose, 0.1% (m/v) FeSO4, and 1.2% (m/v) K2HPO4] for Pseudoalteromonas SP48 growth. Based on these results, optimum fermentation conditions were further explored in a 5L fermentation cylinder using a uniform design; the influence of variables such as incubation time, carbon type, and rotation speed were tested. The optimal fermentation conditions were fermentation time (42 hr), tryptone (1.1%), seeding volume (1.4 × 1013 cells), and rotation speed (250 r/min). Under these established optimum conditions, the biomass of strain SP48 increased by 79.2% and its lethal dose 50% (LD50) decreased by 54.0%, respectively. The TEM results showed that compared with the control group, the cell wall and cell membrane of A. tamarense were significantly damaged, and the structure and shape of the organelles were destroyed by algicidal bacteria of Pseudoalteromonas SP48. Overall, our results demonstrate that the optimized culture conditions could significantly enhance the algicidal activity of Pseudoalteromonas SP48 against a harmful dinoflagellate, such as A. tamarense. It will effectively provide a scientific foundation for both production of algicidal substances and HABs control.

The present study was carried out in order to investigate the removal of soluble Mn from an aqueous solution using Bacillus cereus. A manganese aqueous solution at 50 mg L was treated, and the product was less than 1 mg L of residual concentration, which complied with environmental regulations. Before the optimization, B. cereus was able to remove Mn ions from an aqueous solution; however, the residual content was around 2.5 mg L. Screening experiments aiming at defining the effects of the growth medium composition indicated that both casamino acid-peptone and yeast extract contributed to manganese removal. These experiments also showed the interaction between these two components of the culture media, nevertheless the use of glucose did not prove significant. Considering these observations, the Doehlert design was used to generate a response surface. The model was significant with the p value lower than 0.05 and the lack-of-fit not significant ( p > 0.05). The optimized composition of the growth medium was defined as 0.5 g L of casamino acid-peptone and 0.25 g L of yeast extract, whereas glucose could be removed from the original growth medium. When the optimized condition of the growth medium was used, the time required for manganese removal was reduced from 21 to 8 days. After optimization, B. cereus was capable of producing high manganese removal, reducing the residual concentration to levels below 1.0 mg L. [ABSTRACT FROM AUTHOR]

Vicia faba callus line (VFS 1), isolated from expiants of immature embryo, grew satisfactorily on Murashige and Skoog complete medium with 1.38 μM 2,4-D, or with 0.92 μM 2,4-D to which 1.0 μM kinetin was added. It also grew well on the B 5 modified medium containing 2.3 μM 2,4-D and 25.0 μM kinetin. On the last of these media the cultures grew more uniformly and without necrosis. They also showed diminishing variation in polyploidy in favour of diploids and corresponding aneuploids (hypodiploids). After being cultured for nearly three years on MS containing 1.38 μM 2,4-D, 8-33% of cultures of VFS 1 were able to regenerate roots when transferred to either MS half strength with 5.37 μM NAA, or to a medium without 2,4-D, or else to media with the addition of kinetin only (in various concentrations). [ABSTRACT FROM AUTHOR]

Bacteria play an important role in preventing algal blooms and reducing their harm to the environment. To improve the algicidal activity of Pseudoalteromonas SP48 which had an inhibition effect on dinoflagellate Alexandrium tamarense, its growth medium and fermentation conditions were optimized for this bacterium. In this study, we used two steps to establish the optimum conditions. First, the proper proportion of medium was selected based on an orthogonal design. Then, the fermentation conditions were further optimized through uniform design in an enlarged 5L bioreactor. To test the algicidal ability of Pseudoalteromonas SP48 under the optimum conditions, algal cell morphology was observed by transmission electron microscopy (TEM). After the orthogonal design, we found that the optimum medium was [0.7% (m/v) tryptone, 0.2% (m/v) soluble starch, 0.2% (m/v) sucrose, 0.1% (m/v) FeSO 4 , and 1.2% (m/v) K 2 HPO 4 ] for Pseudoalteromonas SP48 growth. Based on these results, optimum fermentation conditions were further explored in a 5L fermentation cylinder using a uniform design; the influence of variables such as incubation time, carbon type, and rotation speed were tested. The optimal fermentation conditions were fermentation time (42 hr), tryptone (1.1%), seeding volume (1.4 × 10 13  cells), and rotation speed (250 r/min). Under these established optimum conditions, the biomass of strain SP48 increased by 79.2% and its lethal dose 50% (LD 50 ) decreased by 54.0%, respectively. The TEM results showed that compared with the control group, the cell wall and cell membrane of A. tamarense were significantly damaged, and the structure and shape of the organelles were destroyed by algicidal bacteria of Pseudoalteromonas SP48. Overall, our results demonstrate that the optimized culture conditions could significantly enhance the algicidal activity of Pseudoalteromonas SP48 against a harmful dinoflagellate, such as A. tamarense. It will effectively provide a scientific foundation for both production of algicidal substances and HABs control., (© 2019 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)