Goldman J C, Dennett M R, Riley C B
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543.
Biotechnol Bioeng. 1982 Mar;24(3):619-31. doi: 10.1002/bit.260240308.
The freshwater alga Scenedesmus obliquus was grown in continuous culture at a fixed dilution rate of 0.5/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(2)-enriched air into the cultures and by varying the source of nitrogen (NO(3) (-), NH(4) (+), or urea) in the growth medium, which, in turn, led to changes in culture alkalinity. Culture alkalinity and P(CO(2) ) were the sole determinants of pH. A pH-stat system, together with NO(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 of large-scale algal cultures. NH(4) (+) is a poor source of N because it leads to destruction of culture alkalinity and concomitant growth-inhibiting reductions in pH, whereas NO(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 maximizing algal yield when it is supplied in combination with the proper amounts of HCO(3) (-) alkalinity in the growth medium and percent CO(2) in the bubbled gas that will lead to an equilibrium pH near the optimum pH.
淡水绿藻斜生栅藻以固定的稀释率0.5/天进行连续培养，但pH值在4.17 - 10.67范围内变化。通过向培养物中持续鼓入含1%二氧化碳的富氧空气，并改变生长培养基中的氮源（硝酸根离子、铵离子或尿素），将pH值调节在4.17 - 7.67范围内，这反过来又导致培养物碱度发生变化。培养物碱度和二氧化碳分压是pH值的唯一决定因素。使用pH自动控制体系以及培养基中的硝酸根离子，将pH值调节在7.92 - 10.67范围内。在pH 6.6时出现的最大生产力仅在一定程度上取决于氮源，因为培养物碱度是氮吸收的函数。结果表明，氮源的选择是控制大规模藻类培养pH值的关键因素。铵离子是一种较差的氮源，因为它会导致培养物碱度的破坏以及随之而来的pH值降低从而抑制生长，而硝酸根离子则有相反的效果，尽管在这种情况下pH值受到的影响没有那么严重。到目前为止，当尿素与生长培养基中适量的碳酸氢根碱度以及鼓入气体中适当百分比的二氧化碳一起供应时，它是使藻类产量最大化的最合适氮源，这将导致平衡pH值接近最佳pH值。
