Light respiration in Chlorella sorokiniana

Area of Science:

• Microalgal physiology
• Photosynthesis and respiration dynamics

Background:

• Respiration and photosynthesis occur simultaneously in microalgae under light.
• Accurate measurement of respiration is crucial for understanding microalgal growth.
• Existing methods may disturb microalgal cultures.

Purpose of the Study:

• To develop a rapid, in situ method for measuring oxygen uptake rate (OUR) in Chlorella sorokiniana.
• To investigate the relationship between respiration rate and microalgal growth rate.
• To determine if respiration fulfills the maintenance requirements of microalgae.

Main Methods:

• Utilized fiber-optic oxygen microsensors for in situ measurement of immediate post-illumination respiratory O(2) uptake rate (OUR).
• Employed a simple extension to the cultivation system for rapid, non-disruptive measurements.
• Measured net oxygen production rate (net OPR) online to calculate gross oxygen production rate (gross OPR).

Main Results:

• The developed method allows for rapid (minute-scale) and frequent OUR measurements without disturbing microalgal cultivation.
• Gross OPR was 35-40% higher than net OPR, indicating significant respiratory activity.
• Specific OUR was highest during early exponential growth and decreased to a stable maintenance level.

Conclusions:

• The rapid OUR measurement method is effective for studying microalgal respiration.
• Increased microalgal growth rate correlates with higher respiration rates, likely due to increased energy demands.
• The measured respiration rate at the end of the batch culture aligns with the maintenance energy requirement for C. sorokiniana.