Cultivation technology development of Rhodothermus marinus DSM 16675

Abstract

This work presents an evaluation of batch, fed-batch, and sequential batch cultivation techniques for production of R. marinus DSM 16675 and its exopolysaccharides (EPSs) and carotenoids in a bioreactor, using lysogeny broth (LB) and marine broth (MB), respectively, in both cases supplemented with 10 g/L maltose. Batch cultivation using LB supplemented with maltose (LB_malt) resulted in higher cell density (OD₆₂₀ = 6.6) than use of MB_malt (OD₆₂₀ = 1.7). Sequential batch cultivation increased the cell density threefold (OD₆₂₀ = 20) in LB_malt and eightfold (OD₆₂₀ = 14) in MB_malt. In both single and sequential batches, the production of carotenoids and EPSs using LB_malt was detected in the exponential phase and stationary phase, respectively, while in MB_malt formation of both products was detectable in both the exponential and stationary phases of the culture. Heteropolymeric EPSs were produced with an overall volumetric productivity (Q_E) of 0.67 (mg/L h) in MB_malt and the polymer contained xylose. In LB, Q_E was lower (0.1 mg/L h) and xylose could not be detected in the composition of the produced EPSs. In conclusion, this study showed the importance of a process design and medium source for production of R. marinus DSM 16675 and its metabolites.

Keywords: Bioreactor; Carotenoid; Exopolysaccharide; Rhodothermus marinus; Sequential batch cultivation.

Fig. 1

Growth profile of R. marinus DSM 16675 and sugar consumption during batch cultivation in a LB_malt and b MB_malt. Symbols: (filled diamond) cell density represented by OD_620nm, (filled square) concentration of maltose (g/L), (filled triangle) concentration of glucose (g/L)

Fig. 2

Comparison of growth profiles of R. marinus DSM 16675 in batch cultivations in LB and in LB supplemented with glucose in bioreactor. Symbols: (filled diamond) cell growth in LB_glu, (filled circle) cell growth in LB medium, (filled triangle) concentration of glucose in the bioreactor cultivation

Fig. 3

Cell growth and product formation profiles during batch cultivation of R. marinus DSM 16675 in a LB_malt and b MB_malt. Symbols: (filled diamond) cell growth presented as OD_620nm, (filled triangle) total carotenoids absorbance at 450 nm, and (filled square) EPSs concentration (mg/L)

Fig. 4

Changes in total carotenoids absorbance as a function of cell growth represented as OD_620nm in a LBmalt and b MBmalt

Fig. 5

Growth profile of R. marinus DSM 16675 and sugar consumption during a fed-batch cultivation in LB_malt and b repeated fed-batch cultivation in LB_malt. Symbols: (filled diamond) cell growth represented as OD_620nm, and (filled square) maltose concentration (g/L). Feeding was made stepwise, as indicated by arrows

Fig. 6

Growth profile of R. marinus DSM 16675 and sugar consumption during sequential batch cultivation using a LB_malt and b MB_malt. Symbols: (filled diamond) cell growth represented as OD_620nm and (filled square) maltose concentration (g/L)

Fig. 7

Cell growth and product formation profile during sequential batch cultivation of R. marinus DSM 16675 in a LB_malt and b MB_malt. Symbols: (filled diamond) cell growth represented as OD_620nm (filled triangle) total carotenoids absorbance, and (filled square) EPSs concentration (mg/L)

Fig. 8

Changes in total carotenoids absorbance as a function of cell density represented as OD_620nma during sequential batch cultivations with cell recycle for seven batches in LB_malt and b during sequential batch cultivations with cell recycle for four batches in MB_malt

Fig. 9

EPSs volumetric productivity (mg/L  h) of R. marinus DSM 16675 in each batch in cycle sequence of four batches grown in MB_malt. Each cycle was represented by its final OD_620nm