以微藻類水解液生產生質酒精

Fermentation of Microalgae Hydrolysate for Bioethanol Production by Saccharomyces cerevisiae

由於近幾年來全球暖化、化石燃料之即將用罄與原油價格日漸提升，迫使人類不得不尋找可再生、經濟、有效、能永續且同時能降低溫室氣體排放之替代能源，而以可再生生質來生產生質酒精是關鍵選擇方案之一。由於微藻易於培植、生長迅速、為非食用作物、不佔地且有能力快速累積碳水化合物等優點，使其具有相當大潛力作為發酵生產生質酒精之生質原料。本研究探討微藻 Chlorella sp. Y8-1 之最適水解條件及利用水解液於生質酒精的發酵。結果發現微藻水解糖化之最適條件為將 20 g／L 藻粉加入 0.1 N 硫酸溶液，再於高壓滅菌釜（121℃）進行酸水解 60 min，之後調整至 pH 5，加入纖維酶（1 %，w／w）於 50 ℃、100 rpm 反應 12 小時。微藻水解可得葡萄糖產率為 25.9 %（產量 5.19 g／L），半乳糖產率為 8.3 %（1.65 g／L），纖維雙醣產率為 10.4 %（2.08 g／L）。將微藻類水解液作為碳源，並添加 2 g／L Yeast extract，以固定化菌培養方式在30℃ 靜置培養48小時以生產酒精，發現發酵微藻水解液消耗單醣量總和為7.35 g/L並產生 3.50 g／L 酒精，轉化率為 93 %。本研究證實利用連續稀酸／酵素之水解方式與使用Saccharomyces cerevisiae Wu-Y2 發酵微藻水解液可有效以微藻 Chlorella sp. Y8-1 為生質原料來生產生質酒精，在生質能源之發展具有相當大的潛力。

Increasing global energy demands alongside concerns over the depletion of fossil energy resources and significant climate change have compelled people to actively seek alternative fuels that are sustainable, environmentally friendly, and cost efficient. Bioethanol produced from various renewable feedstocks is considered a clean and renewable energy source that ranks among the best options for renewable energy sources. The utilization of microalgal biomass as feedstock for bioethanol production is promising, owing to its numerous advantages such as fast growth rate, low land usage, high carbon uptake rate, nonfood usage, and the ability to accumulate substantial amounts of carbohydrates. The aim of the present study was to investigate the sequential acid/enzymatic hydrolysis of microalgae Chlorella sp. Y8-1 and the fermentation of the hydrolysate by Saccharomyces cerevisiae Wu-Y2, a newly isolated yeast strain, for bioethanol production. The results revealed that the optimal saccharification process was derived when 20 g/L of Chlorella sp. powder was hydrolyzed by 0.1 N H2SO4 and autoclaved（131 °C） for 60 min, followed by adjustment to pH 5, with an addition of 1% cellulase and incubation at 50 °C for 12 h. The main sugars in the hydrolysate for Chlorella sp. were glucose（5.19 g/L; 25.9%, w/w, dry base）, galactose （1.65 g/L; 8.3%, w/w, dry base） , and cellobiose（2.08 g/L; 10.4%, w/w） . The strain of S. cerevisiae Wu-Y2 was observed to effectively utilize the glucose and galactose in the hydrolysate. When the obtained hydrolysates were supplemented with 2 g/L yeast extract, inoculated with 10% of immobilized S. cerevisiae Wu-Y2, and then incubated at 30 °C for 48 h, 7.35 g/L of mono sugars was consumed and 3.50 g/L（93%） of bioethanol was produced from the Chlorella sp. Hydrolysate.