研究中培養的自營性微藻（如擬球藻）是經由光合作用生成養份以維持生長，一般在養分充足的培養環境下，光是影響其生長的主要因子。微藻培養在傳統上是利用平面培養池，但是當微藻濃度變高時，其遮蔽效應變大，造成光線只能穿透部分培養藻液，導致光梯度變大，微藻無法有效率吸收到光，使得其培養效率降低。基於在相同光照面積下，增加其培養深度雖能提高微藻產量，但此方式並不能提升光使用效率，因此設計新型光生化反應器是必要的。
此研究以開放式矩形槽來模擬平面培養池培養微藻，新型光生化反應器是在矩形槽內放置中空透光性平板設計而成。利用光在空氣中傳播會發生散射現象，使得光線會由平板的側面傳送出去，將可改變系統內的光分佈情形，以提高微藻吸收光的機率。為探討反應器內光分佈變化對微藻生長之影響，實驗中應用朗伯—比爾定律(Lambert-Beer’s law)模擬藻類培養系統中光的分佈情形，再經由計算反應器內的平均光強度，及透過藻類的吸收光線係數，將可估算出每單位質量藻類的可吸光值(Fab)。經由估算，新型光生化反應器內的Fab值均比平面培養池高。實驗結果顯示，藻類培養於新型光生化反應器的產率均比平面培養池高，其中以插入 4個寬度為 5 cm平板的反應器最佳，可提升 24 %的產率。証明在提供相同的光照強度下，藻類培養於新型光生化反應器確實可以提升光使用效率。
此外，當藻類濃度變高時，藻類吸收的光逐漸不充足，會使得其生長受到限制。於是當藻類濃度上升時，應用半連續式培養策略，稀釋藻類的濃度，使得其可以吸收到較充足的光進行生長。實驗結果顯示，使用半連續培養策略與批次培養相比，可提升13 %的產率，代表此培養策略的確可提升藻類產率。

關鍵詞 : 微藻、光生化反應器、朗伯—比爾定律、平均光強度、單位質量藻類的可吸光值

Microalgae need to uptake the light to conduct the photosynthesis for growing biomass, In addition, the distribution of light intensity is the key factor for growth kinetic of microalgae. For instances, open pond, is a general photobioreactor to produce microalgae, but the increase of microalgae concentration decreases the light penetration in the cultivated microalgae system caused by shading effect. Since the large gradient of light intensity in depth results low culture efficiency, the photo-bioreactor, which is an open tank inserted some transparent flat-plates, is proposed to remove the concern of large gradient.
In this study, there two kinds of photobioreactors, the open tank and the proposed photobioreactor, are compared by the performance index Fab. Fab means the photon flux absorbed by the unit biomass; and it is derived from Iav, the averaged irradiance inside of the photobioreactor estimated by Lambert-Beer’s law. Since Fab value of the proposed photobioreactors is larger than open tank, the biomass productivity is also higher. Large Fab implies that much light is absorbed by microalgae in the photobioreactor through the sides of hollow flat-plates.
By the experimental observation, the proposed photo-bioreactor, which is composed of the open tank and inserted four 5 cm width flat-plates, performs 24 % better than the common open tank in biomass productivity. And the biomass productivity gains 13 % more, when it is operated in semi-continuous instead of batch modes.

Keywords: Microalgae, Photobioreactor, Lambert-Beer's law, Averaged irradiance, Photon flux absorbed by the biomass unit

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