(732f) Salting-Out Extraction of Bio-Based Chemicals

Salting-out Extraction of Bio-based Chemicals

Jian-Ying Dai, Ya-Qin Sun and Zhi-Long Xiu^*

School of Life Science and Biotechnology, Dalian University of Technology, Dalian116024, China

^*E-mail: zhlxiu@dlut.edu.cn, Tel: +86-411-84706369

Abstract

The bio-refinery from cheap biomass attracts much attention and endeavor, which is mainly focused on the improvement of strains and fermentation. Down-stream processing for bio-based chemicals becomes bottle-neck in industrial production because so many impurities are introduced into the fermentation broths. Here we summerized salting-out extraction (SOE) based on the partition difference of chemicals in two phases consisting of salts and polymer or hydrophilic solvent, hydrophobic solvent, amphipathic chemicals. The effects of solvents and salts on the formation of two phases were introduced as well as its application in the recovery of bio-based chemicals, such as 1,3-propanediol, 2,3-butanediol, acetoin, lactic acid, succinic acid. The diols such as 1,3-propanediol and 2,3-butanediol could be recovered at a yield above 95%, and the recovery of lactic acid also reached 90%, especially from fermentation broths without pretreatment. At the same time, most of the impurities (cells and proteins) were removed in the same step extraction.

For example, in the recovery process of 1,3-propanediol methanol (35%, v/v) and phosphate (to saturation) were directly added into the fermentation broth (pH 10.7). After mixing and standing 98.1% 1,3-propanediol was partitioned to the top phase, meanwhile 99.85% cells, 92.4% proteins, 90.1% formic acid, 76.7% lactic acid, 87% lactic acid, 87% acetic acid, 88.6% succinic acid and 81% fumaric acid were removed from the top phase. If the fermentation broth was treated by a solvent with weaker polarity, the partition coefficient (K) would also decrease. In a SOE system consisted of K₂HPO₄and alcohol, the K value was decreased from 7.87 to 2.4 when the used alcohol was switched from methanol to 2-butanol. 2,3-Butanediol and acetoin demonstrated similar behavior as 1,3-Propanediol. At suitable conditions more than 95% of target product was recovered.

Due to the high hydrophilicity of organic acids, the recovery of organic acids was a little lower compared with diols and acetoin. In a SOE systems composed of 26% methanol and 25% K₂HPO₄ (w/w) 86% lactic acid was recovered, while in a system consisted of 30% ethanol and 14% K₂HPO₄ (w/w) the recovery was 90.6%.

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