Liu Li-Ping, Zong Min-Hua, Linhardt Robert J, Lou Wen-Yong, Li Ning, Huang Chao, Wu Hong
School of Bioscience and Bioengineering, South China University of Technology, Guangzhou Higher Education Mega Centre, 382 East Waihuan Rd., Panyu District, Guangzhou, 510006 China.
School of Food Science and Engineering, South China University of Technology, Room 409, Building 13, 381 Wushan Rd., Tianhe District, Guangzhou, 510640 China.
Biotechnol Biofuels. 2016 Dec 16;9:266. doi: 10.1186/s13068-016-0682-z. eCollection 2016.
Ionic liquid (IL) pretreatment has emerged as a promising technique that enables complete utilization of lignocellulosic biomass for biofuel production. However, imidazolium IL has recently been shown to exhibit inhibitory effect on cell growth and product formation of industrial microbes, such as oleaginous microorganisms. To date, the mechanism of this inhibition remains largely unknown.
In this study, the feasibility of [Bmim][OAc]-pretreated rice straw hydrolysate as a substrate for microbial lipid production by , also known as , was evaluated. The residual [Bmim][OAc] present in the hydrolysate caused a reduction in biomass and lipid content (43.6 and 28.1%, respectively) of , compared with those of the control (7.8 g/L and 52.6%, respectively). Seven imidazolium ILs, [Emim][DEP], [Emim]Cl, [Amim]Cl, [Bmim]Cl, [Bzmim]Cl, [Emim][OAc], and [Bmim][OAc], capable of efficient pretreatment of lignocellulosic biomass were tested for their effects on the cell growth and lipid accumulation of to better understand the impact of imidazolium IL on the lipid production. All the ILs tested inhibited the cell growth and lipid accumulation. In addition, both the cation and the anion of IL contributed to IL toxicity. The side chain of IL cations showed a clear impact on toxicity. On examining IL anions, [OAc] was found to be more toxic than those of [DEP] and Cl. IL exhibited its toxicity by inhibiting sugar consumption and key enzyme (malic enzyme and ATP-citrate lyase) activities of . Cell membrane permeability was also altered to different extents in the presence of various ILs. Scanning electron microscopy revealed that IL induces fibrous structure on the surface of cell, which might represent an adaptive mechanism of the yeast to IL.
This work gives some mechanistic insights into the impact of imidazolium IL on the cell growth and lipid accumulation of oleaginous yeast, which is important for IL integration in lignocellulosic biofuel production, especially for microbial lipid production.
离子液体（IL）预处理已成为一种很有前景的技术，能够实现木质纤维素生物质在生物燃料生产中的完全利用。然而，最近研究表明咪唑鎓离子液体对工业微生物（如产油微生物）的细胞生长和产物形成具有抑制作用。迄今为止，这种抑制作用的机制仍不清楚。
在本研究中，评估了经[Bmim][OAc]预处理的稻草水解产物作为斯达氏油脂酵母（也称为产油油脂酵母）生产微生物油脂的底物的可行性。与对照（分别为7.8 g/L和52.6%）相比，水解产物中残留的[Bmim][OAc]导致斯达氏油脂酵母的生物量和脂质含量分别降低了43.6%和28.1%。测试了七种能够有效预处理木质纤维素生物质的咪唑鎓离子液体，即[Emim][DEP]、[Emim]Cl、[Amim]Cl、[Bmim]Cl、[Bzmim]Cl、[Emim][OAc]和[Bmim][OAc]，以研究它们对斯达氏油脂酵母细胞生长和脂质积累的影响，从而更好地了解咪唑鎓离子液体对油脂生产的影响。所有测试的离子液体均抑制细胞生长和脂质积累。此外，离子液体的阳离子和阴离子都对其毒性有影响。离子液体阳离子的侧链对毒性有明显影响。在研究离子液体阴离子时，发现[OAc]比[DEP]和Cl的毒性更大。离子液体通过抑制斯达氏油脂酵母的糖消耗和关键酶（苹果酸酶和ATP-柠檬酸裂解酶）活性来表现其毒性。在不同离子液体存在的情况下，细胞膜通透性也会发生不同程度的改变。扫描电子显微镜显示，离子液体在斯达氏油脂酵母细胞表面诱导出纤维状结构，这可能代表了酵母对离子液体的一种适应性机制。
本研究为咪唑鎓离子液体对产油酵母细胞生长和脂质积累的影响提供了一些机制性见解，这对于离子液体在木质纤维素生物燃料生产（尤其是微生物油脂生产）中的应用具有重要意义。
