以甘蔗渣廢棄物生產生質酒精之研究

Biorefining of Sugarcane Bagasse for Bioethanol Production

石油危機爆發後，世界各國積極尋找可替代能源，而生質能源是利用農業廢棄物、林業加工廢料、藻類與城市垃圾中所含的廢棄生質經轉換技術產生可供利用的能源。這些廢棄生質原料中都含有大量的木質纖維素，可經糖化及發酵方式轉化為生質酒精，是目前最具潛力且廣為利用之替代能源之一。本研究使用全球儲存量較高、價格較低、利用率也偏低的纖維素農業廢棄物──甘蔗渣作為生產生質酒精之原料。將廢棄甘蔗渣進行水解成可發酵糖，並分析成分及產率，甘蔗渣水解液則進行發酵以生產生質酒精。本研究結果得知甘蔗渣成份中含有全纖維64.05%、木質素11.26%、灰分1.62%，其中全纖維包括纖維素以及半纖維素。以2g蔗渣添加0.25NH2SO4（固液比1:50），經131℃高溫高壓，反應20min進行酸水解，可得葡萄糖（Glucose）3.0 g/L （15.0%）、木糖（Xylose）2.3 g/L（11.5%），再經纖維水解酵素水解後，最終之葡萄糖（Glucose） 與木糖（Xylose）之濃度（產率）分別為 Glucose 7.1 g/L（35.5%）、Xylose 2.8 g/L（14.0 %）。 以酵母菌（Pichia stipitis Pignal BCRC21777）發酵蔗渣之酸水解液，結果發現當以蔗渣酸水解液當作碳源（葡萄糖 3 g/L、木糖 2.3 g/L）、Yeast extract 12 g/ L 做為氮源，於 24℃，100 rpm， 培養 72 小時，葡萄糖與木糖完全消耗（共 5.3 g/L，100 %），可得酒精產量 2.3 g/ L，酒精轉化率為 86%。

Concern over the depletion of fossil fuels has shifted global trends from fossil fuel reliance toward alternative renewable fuel development from biobased resources. Production of second-generation bioethanol, a clean and renewable energy, from agricultural crop residues mainly containing lignocellulosic biomass can improve the sustainability of feedstock production without competing with food production for the cultivation of farmland. Sugarcane bagasse is the most abundant lignocellulosic material in tropical countries and an ideal feedstock for bioethanol production. This study investigated biorefining of sugarcane bagasse for bioethanol production. Results showed that acid hydrolysis of bagasse（solid to liquid ratio 1:50）through treatment with 0.25 N sulfuric acid at 131°C for 20 min resulted in glucose（3.0 g/L, 15.0%）and xylose（2.3 g/L, 11.5%）. The acid hydrolysate was added to 1% commercial cellulase and then further hydrolyzed at a pH of 4.5, a temperature of 50°C, and 100 rpm. Glucose（7.1 g/L, 35.5%）and xylose（2.8 g/L, 14.0%）were obtained after 3 h of incubation. Overall, 77.3% of sugars from the polysaccharides of bagasse can be released through this treatment. The acid hydrolysate containing glucose（3.0 g/L）and xylose（2.3 g/L） was supplemented with 12 g/L yeast extract and fermented by Pichia stipitis Pignal BCRC21777 at 24°C and 100 rpm for 72 h. Then, glucose and xylose were completely consumed（total 5.3 g/L, 100%） and bioethanol（2.3 g/L）was produced. The bioethanol conversion efficiency was 86%.