Effect of nitrogen-mediated changes in alkalinity on ph control and CO/sub 2/ supply in intensive microalgal cultures
The freshwater alga Scenedesmus obliquus was grown in continuous culture at a fixed dilution rate of 0.5 per day, but at varying pH in the range 4.17-10.67. The pH was regulated in the range 4.17-7.67 by continuously bubbling 1% CO/sub 2/-enriched air into the cultures and by varying the source of nitrogen (NO/sub 3/-, NH/sub 4/+, or urea) in the growth medium, which, in turn, led to changes in culture alkalinity. Culture alkalinity and PCO/sub 2/ were the sole determinants of pH. A pH-stat system, together with NO/sub 3/- in the medium, was used to regulate the pH in the range 7.92-10.67. Maximum productivity, which occurred at pH 6.6, was dependent on N source only to the extent that culture alkalinity was a function of nitrogen uptake. The results demonstrate that the choice of N is a critical factor in controlling the pH+ large-scale algal cultures. NH/sub 4/+ is a poor source of N because it leads to destruction of culture alkalinity and concomitant growth-inhibiting reductions in pH, whereas NO/sub 3/- has an opposite effect, although pH is not so severely affected in this case. Urea is, by far, the most suitable N source for maximising algal yield when it is supplied in combination with the proper amounts of HCO/sub 3/- alkalinity in the growth medium and percent CO/sub 2/ in the bubbled gas that will lead to an equilibrium pH near the optimum pH. (Refs. 23).
- Research Organization:
- Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
- OSTI ID:
- 5034665
- Journal Information:
- Biotechnol. Bioeng.; (United States), Vol. 24:3
- Country of Publication:
- United States
- Language:
- English
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09 BIOMASS FUELS
CULTURE MEDIA
COMPARATIVE EVALUATIONS
PH VALUE
SCENEDESMUS
CONTINUOUS CULTURE
CARBON DIOXIDE
NITROGEN
NUTRIENTS
UREA
ALGAE
AMIDES
CARBON COMPOUNDS
CARBON OXIDES
CARBONIC ACID DERIVATIVES
CHALCOGENIDES
ELEMENTS
MICROORGANISMS
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ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLANTS
UNICELLULAR ALGAE
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