THE EFFECT OF PH ON GROWTH RATE, BIOCHEMICAL COMPOSITION AND EXTRACELLULAR CARBOHYDRATE PRODUCTION OF THE MARINE DIATOM SKELETONEMA COSTATUM

M. Taraldsvik, S.M. Myklestad-2000

European Journal of Phycology, 35 (2) : 189-194 (from Current Contents)

Abstract :

The marine diatom Skeletonema costatum was grown at different pH values in a semicontinuous cultivation system which kept the pH at a pre-set value. Growth rate was nearly constant at pH 6.5-8.5 (average 2.4 divisions day-l) and declined at pH > 9. Organic carbon (C) production decreased from an average of 5.3 mg l(-1) at pH 6.5-8.5 to 2 and 1 mg l(-1) at pH 9.0 and 9.4, respectively. Storage beta-1,3-linked glucan decreased from a high of 7.1 mg l(-1) at pH 6.5 to 0.2 mg l(-1) at pH 9.4 and, concomitantly, the percentage of total organic C as glucan C decreased from 60% to 10%. Cellular concentration of amino acids varied from about 62 to 8 mM over the pH range 8.0-9.4. At pH 9.4 the concentration of: glutamine was below the detection limit. The extracellular production of carbohydrates in the pH range 6.5-8.5 was only 3.7% (average) of total C production and increased at pH 9.0 and 9.4. The decrease in growth rate at pH > 9.0 might be caused by a decrease in the rate of some important biochemical reactions, as well as by a change in cell membrane properties in this pH range.

(Norwegian Univ Sci & Technol, Dept Biotechnol, N-7491 Trondheim, Norway, e-mail of S.M. Myklestad: Sverre.Myklestad-@chembio.ntnu.no)

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