微藻富含許多的有益成分，例如：特用化學品、多元不飽和脂肪酸、維生素及多醣體等，因此奠定了微藻在各個領域的應用價值。台灣因為缺乏廣闊的半封閉海灣地形，加上颱風、光照等氣候變化因素，因此並不適合開發大面積的海藻培育場。而受到成本效益的考量，大部分都選擇小型開放式的陽光池培養模式，但其缺點為培養環境易受外來物種的污染而影響產物品質。因此，以穩定的小規模/實驗室環境(即光生物反應器)進行養殖，將可落實產品質與量的品管控制以提升產業發展。然而，在密閉空間下養殖往往因為養分不足或是培養基置換不易而導致產量不足的問題，由此本研究提出建構一駐波聲場光生物反應器系統(Ultrasound Standing Wave Field-Incorporated Photobioreactor System；U-PBRS)，於密閉系統下得以半自動化的方式更換培養基，以持續提供微藻生長足夠的營養，藉此提高單位體積內微藻的生物質和生物脂質產量，而因此提升整體養殖之效能。本研究選用擬球藻作為實驗標的微藻細胞。由於擬球藻富含二十碳五烯酸(Eicosapentaenoic acid；EPA)，使的該藻種在具有極高的經濟價值。本實驗所設定的最佳超聲波駐波場(Ultrasound Standing Wave Field；USWF)參數為1 MHz 的頻率；8 W/cm2的輸出能量；系統流率為2 mL/min，於培養總體積30 mL，操作時間2小時下，細胞總收集率可高達90 ％。此外，為了評估此參數下對於細胞是否有毒性或傷害性，經實驗結果顯示，擬球藻細胞的生長及生理並沒有差異(P = NS)。於此為基礎，我們進一步的以建構的U-PBRS來進行微藻培養，每三天置換培養基，十二天後我們發現置換培養基的組別(實驗組)，相較於不置換培養基(對照組)的組別細胞濃度提高了1.4倍；生長質量增加了2.6倍；生物脂質增加了2倍，而EPA的產也增加了2倍。綜合以上結果，以本研究所建構的U-PBRS有效地提升了密閉式微藻養殖的效能。

Microalgae have long been recognized as one of the most economical bio-resources for live feed, pharmaceuticals, and alternative fuels since they can provide abundance of essential chemicals such as proteins and polysaccharides. Due to lack of a broad semi-enclosed bay topography and concerns of typhoon and climate-related issues, it is not suitable for Taiwan to build up an open, large-area pool for massive microalgal cultivation. Therefore, the methods using various small-scale open pools are usually conducted nowadays. However, such open environment is prone to be contaminated by exogenous species and thereby the quality of the cells is affected. Photobiorectors, in which the culture environment can be precisely controlled, provide an alternative for microalgal growth without aforementioned drawbacks. However, limited amount of nutrient and/or cumbersome procedures for culture medium change greatly hinder the productivity of photobioreactor-based microalgal culture. To overcome these challenges, we proposed to establish an Ultrasound Standing Wave Field (USWF)-Incorporated Photobioreactor System; U-PBRS, which enables to semi-automatically change medium and persistently maintain the nutrient-enriched environment for microalgal cultivation throughout the culture process to enhance the culture efficiency. In this study, the Nannochloropsis oculata (N. oculata), which is enriched with eicosapentaenoic acid (EPA), was selected as the experimental microalga cells. The optimized USWF was set at 1 MHz of frequency, 8 W/cm2 of output energy; and flow rate of 2 mL min by which the cell collection rate can be obtained by up to 90% under 2 h of operation for total volume of 30 mL, and such USWF setting was ineffective to cells no matter in cellular growth and/or in lipid production (P = NS for each). In terms of the productions of N. oculata cultured by U-PBRS for 12 days in which the medium was changed every 3 days, our data showed that the yielded cell concentration, biomass, biolipid and EPA significantly enhanced 1.4, 2.6, 2, and 2 folds, respectively, as compared to the group without medium change. Overall the U-PBRS developed in this study effectively promoted the efficiency of microalgal culture operation in closed setting and thereby exhibited a high potential for use in massive microalgal cultivation.

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