介质pH缓冲系统选择及其对龙须菜生长的影响

该文选择红藻门大型植物龙须菜(Gracilaria lemaneiformis)作为研究对象,通过黑白瓶法筛选出有机试剂POPSO(哌嗪-N,N-双(2-羟基乙烷磺酸)),能较好地缓冲室内龙须菜培养中介质pH的波动。在此基础上,探讨了POPSO对龙须菜生长的影响,结果表明:15 mmol·L ^-1及以上浓度的POPSO能较好地稳定介质pH值,减少系统中DIC浓度的急剧变化,但POPSO对CO₂浓度波动不起作用;试验结果还表明,介质中的CO₂浓度与龙须菜的生长速率间存在着类似酶动力学方程的关系,当介质中的CO₂浓度下降到5.25 μmol·L ^-1以下时,龙须菜生长出现抑制现象。相对稳定pH的培养环境,更有利于介质DIC中的HCO^-₃、CO^2-₃向CO₂的转换,缓解龙须菜生长的C抑制。

pH BUFFER SELECTION AND ITS EFFECT ON GROWTH OF GRACILARIA LEMANEIFORMIS

Background and Aims We examined the effect of acid-alkaline concentrations in media on growth rate and nutrient uptake of a red macroalga, Gracilaria lemaneiformis, which has a rapid growth rate, rapid nutrient uptake rate, and high agar content. We address the following questions: 1) can the culture media be kept relatively stabilized, 2) what organic compound best buffers pH, and 3) how does the compound buffer the media and affect growth of the alga?Methods Utilizing the dark-light bottles method, we selected a suitable zwitterionic organic compound from seven reagents (barbitone, borate, HEPES, TRIS, MOPS, TAPS, POPSO) that did not inhibit photosynthetic production of dissolved oxygen (DO), did not increase depletion of DO in respiration, and adjusted acid-alkaline balance in the culture media. We examined the effects of each buffer on growth rate (SGR) of G. lemaneiformis, measured diurnal and weekly variations of pH and dissolved inorganic carbon (DIC), and determined CO₂ concentrations according to pH and DIC. We integrated these with the growth rate of G. lemaneiformis, to investigate the mechanisms of growth and carbon uptake.Key Results POPSO was the zwitterionic organic compound that best met our objectives. During the diurnal experiment of POPSO's effect on algal growth, pH rose continuously during the light cycle, contrary to DIC; however, high concentration of POPSO can buffer this fluctuation. During the one-week experiment, according to results of the diurnal experiment, pH values and DIC at the beginning and end of the light cycle indicated that lower concentrations of POPSO (0 and 5 mmol·L^-1) did not buffer pH fluctuations, but higher concentrations (>15 mmol·L^-1) suitably stabilized pH values and leveled off DIC content in the media. Ambient CO₂ concentration determined algal growth rates, with the relationship between SGR of G. lemaneiformis and ambient CO₂ concentration similar to a Michaelis-Menton kinetics equation. The saturated concentration of CO₂ was 5.25 μmol·L^-1, and the maximum growth rate of the alga was 10.11%·d^-1.Conclusions This study determined that POPSO is a suitable organic compound to buffer G. lemaneiformis culture media. A possible mechanism is that, under relative stabilization of acid-alkaline media, HCO^-₃and CO^2-₃(components of DIC), transformed into CO₂ and accelerated growth rate of the alga.