Aghazadeh Mahdieh, Ladisch Michael R, Engelberth Abigail S
Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, IN, 47907.
Dept. of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN, 47907.
Biotechnol Prog. 2016 Jul 8;32(4):929-37. doi: 10.1002/btpr.2282. Epub 2016 May 4.
Acetic acid is introduced into cellulose conversion processes as a consequence of composition of lignocellulose feedstocks, causing significant inhibition of adapted, genetically modified and wild-type S. cerevisiae in bioethanol fermentation. While adaptation or modification of yeast may reduce inhibition, the most effective approach is to remove the acetic acid prior to fermentation. This work addresses liquid-liquid extraction of acetic acid from biomass hydrolysate through a pathway that mitigates acetic acid inhibition while avoiding the negative effects of the extractant, which itself may exhibit inhibition. Candidate solvents were selected using simulation results from Aspen Plus™, based on their ability to extract acetic acid which was confirmed by experimentation. All solvents showed varying degrees of toxicity toward yeast, but the relative volatility of ethyl acetate enabled its use as simple vacuum evaporation could reduce small concentrations of aqueous ethyl acetate to minimally inhibitory levels. The toxicity threshold of ethyl acetate, in the presence of acetic acid, was found to be 10 g L(-1) . The fermentation was enhanced by extracting 90% of the acetic acid using ethyl acetate, followed by vacuum evaporation to remove 88% removal of residual ethyl acetate along with 10% of the broth. NRRL Y-1546 yeast was used to demonstrate a 13% increase in concentration, 14% in ethanol specific production rate, and 11% ethanol yield. This study demonstrated that extraction of acetic acid with ethyl acetate followed by evaporative removal of ethyl acetate from the raffinate phase has potential to significantly enhance ethanol fermentation in a corn stover bioethanol facility. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:929-937, 2016.
由于木质纤维素原料的组成，乙酸被引入纤维素转化过程中，这在生物乙醇发酵中对经过驯化的、基因改造的和野生型酿酒酵母产生显著抑制作用。虽然酵母的驯化或改造可能会降低抑制作用，但最有效的方法是在发酵前去除乙酸。这项工作通过一种途径解决了从生物质水解物中液 - 液萃取乙酸的问题，该途径既能减轻乙酸的抑制作用，又能避免萃取剂本身可能产生抑制作用的负面影响。基于它们萃取乙酸的能力，利用Aspen Plus™的模拟结果选择了候选溶剂，并通过实验进行了确认。所有溶剂对酵母都表现出不同程度的毒性，但乙酸乙酯的相对挥发性使其能够使用，因为简单的真空蒸发可以将少量的乙酸乙酯水溶液浓度降低到最低抑制水平。发现在有乙酸存在的情况下，乙酸乙酯的毒性阈值为10 g L⁻¹。使用乙酸乙酯萃取90%的乙酸，然后通过真空蒸发去除88%的残留乙酸乙酯以及10%的发酵液，从而提高了发酵效率。使用NRRL Y - 1546酵母证明乙醇浓度提高了13%，乙醇比生产率提高了14%，乙醇产率提高了11%。本研究表明，用乙酸乙酯萃取乙酸，然后从萃余相中蒸发去除乙酸乙酯，有可能显著提高玉米秸秆生物乙醇工厂中的乙醇发酵效率。© 2016美国化学工程师学会生物技术进展，32:929 - 937，2016。
