Qingdao Energy Institute analyzed the relevant mechanism of microalgae biofilm adherent culture

Biofilm adherent culture has great advantages of high light efficiency, high yield, easy harvest and efficient water saving, and is one of the transformative cultivation technologies to break through the bottleneck of microalgae production efficiency and cost. In the past ten years, biofilm adherent culture has received extensive and continuous attention at home and abroad.

However, unlike the traditional open pool and photoreactor suspension culture of microalgae, the photocarbon transport and growth mechanism of microalgae biofilms has been unclear. How are light and dissolved inorganic carbon transported within microalgae biofilms? How is it decayed? How deep can it penetrate? Where does photosynthesis take place? How do biofilms thicken? How do environmental factors control biofilm growth? Recently, Liu Tianzhong, a researcher at the Qingdao Institute of Bioenergy and Process Research of the Chinese Academy of Sciences, gave the answer.

The microalgae biotechnology research group led by Liu Tianzhong used automatic cytosol simulation technology combined with experimental research to systematically analyze the transport process of light and dissolved carbon in microalgae biofilm under different culture conditions and CO2 carbon replenishment mode, and revealed the distribution characteristics, surface morphology formation and biofilm growth mechanism of photocarbon in biofilm. The results were recently published in the Chemical Industry Journal “CIESC Journal”. The results of this study lay a theoretical foundation for the optimal design and intensification of the culture process of microalgae biofilm adherent culture reactor.

Qingdao Energy Institute analyzed the photocarbon transport and growth mechanism of microalgae biofilm adherent culture Photo courtesy of the research group

Under the suspension culture of microalgae, algae cells can use liquid circulation to achieve nutrient mixing and shuttle in light and dark areas, but the position of microalgae cells in the biofilm is fixed, light can only be transmitted through cell transmission and intercellular refraction, and carbon is mainly transmitted through intercellular seepage diffusion.

It is found that microalgae biofilms have strong light transmission resistance, and the maximum penetration depth of light is only 30-70 microns, so the light transmission depth is the most important factor restricting the growth of microalgae biofilms. Due to the seepage of the medium, the carbon transfer resistance is not large, and the carbon distribution is relatively sufficient.

Microalgae biofilm can be divided into “photosynthetic growth area” and “dormant area”, photosynthesis only occurs in the upper part of the biofilm 40-70 microns thick “photosynthetic growth area”, cells continue to divide – insert – mature and grow – then divide, the whole process continues to raise the “photosynthetic growth area” and thicken the biofilm. Increasing biofilm thickness eventually leads to a decrease in carbon concentration near the membrane surface, limiting continued growth. Microalgae biofilm culture enhancement strategies to increase light intensity, increase medium carbon concentration, timely harvesting, and bidirectional carbon supplementation were proposed.

Since the method and principle of microalgae biofilm culture were proposed in 2013, a series of progress has been made in this technical field, and more than 30 papers have been published. A fixed CO2 pilot system for spirulina adherent culture was established in Pingdu, Qingdao and Ordos, Inner Mongolia. The above research provides important process theory and technical support for the use of microalgae biofilm adherent culture technology to achieve efficient carbon sequestration and efficient biomass production.

The research was supported by the Key R&D Program of the Ministry of Science and Technology of the “Blue Granary”, the National Natural Science Foundation of China and the Shandong Yuan Research Institute. (Source: China Science News, Liao Yang, Kong Fengru)

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