气提法弱化超高浓度乙醇发酵过程中自絮凝酵母振荡行为

超高浓度(very high gravity,VHG)连续乙醇发酵过程中的振荡行为会导致发酵终点的乙醇浓度振荡和降低,是VHG连续乙醇发酵面临的主要问题。研究表明,游离酵母Saccharomyces cerevisiae 4126和自絮凝酵母BHL01在VHG连续乙醇发酵过程中,生物量、残糖、乙醇、甘油等发酵参数都呈现130～145 h的周期性振荡,且絮凝酵母发酵体系的平均乙醇浓度和乙醇生产强度都明显高于游离酵母体系。在絮凝酵母VHG连续乙醇发酵过程中利用发酵尾气气提分离乙醇,酵母细胞振荡行为被明显弱化,达到拟稳态状态,并且使发酵液中的残糖浓度控制在0.1 g·L^-1以下,平均乙醇浓度为110.87 g·L^-1,乙醇产率达到2.99 g·L^-1·h^-1。因此,本研究为弱化VHG连续乙醇发酵中的参数振荡行为提供了新的技术手段。

Oscillation attenuation by gas stripping in continuous very high gravity ethanol fermentation by self-flocculating yeast

Process oscillation is the main challenge in continuous very high gravity(VHG)ethanol fermentation,which could result in oscillation and decrease of ethanol concentration.In the present study,during continuous VHG ethanol fermentation by free cell Saccharomyces cerevisiae 4126 and self-flocculating yeast BHL01,sustained process oscillations of biomass,residual glucose,ethanol and glycerol,were observed with a period of 130-145 h.Furthermore,in the self-flocculating yeast system,ethanol concentration and productivity were higher than those in the free yeast system.VHG oscillation was significantly attenuated and then a quasi-steady state was developed instead,when gas stripping with fermentative off-gas was used to separate ethanol during continuous VHG ethanol fermentation by self- flocculating yeast.Finally,the residual glucose kept below 0.1 g·L^-1,and ethanol concentration and productivity were 110.87 g·L^-1 and 2.99 g·L^-1·h^-1,respectively.The present study provides a new strategy for the attenuation of oscillation in continuous VHG ethanol fermentation.