Institute of Applied Ecology, Chinese Academy of Sciences, 72 Wenhua Road, Shenhe District, Shenyang City, Liaoning Province 110016, People's Republic of China.
Department of Chemistry and Chemical Engineering, Beijing Forestry University, 35 Qinghua East Road, Haidian District, Beijing 100083, People's Republic of China.
Biotechnol Biofuels. 2013 Nov 14;6(1):161. doi: 10.1186/1754-6834-6-161.
Recently, interest in the utilization of corncob residue (CCR, with high lignin of 45.1%) as a feedstock for bioethanol has been growing. Surfactants have been one of the most popular additives intended to prevent the inhibitory effect of lignin on cellulolytic enzymes, thereby improving hydrolysis. In this study, the effects of biosurfactant tea saponin (TS) on the enzymatic hydrolysis of CCR and the bonding behavior of cellulolytic enzymes to the substrate were investigated. The surface tension in the supernatant was also detected to obtain information about the characteristics and stability of TS.
The glucose concentration was 17.15 mg/mL at 120 hours of hydrolysis with the low loading of cellulolytic enzymes (7.0 FPU/g cellulose and 10.5 BGU/g cellulose) and 5% CCR. The optimal dosage of TS was its critical micelle concentration (cmc, 1.80 mg/mL). The glucose yield was enhanced from 34.29 to 46.28 g/100 g dry matter by TS. The results indicate that TS can promote the adsorption of cellulolytic enzymes on the substrate and mediate the release of adsorbed enzymes. Meanwhile, TS improves the recovery of the cellulolytic enzymes after a hydrolysis cycle and prevents deactivation of the enzymes during the intense shaking process. The surface tension in supernatants of digested CCR with TS remained at 50.00 mN/m during the course of hydrolysis. It is interesting to note that biosurfactant TS can maintain the surface tension in supernatants, despite its digestibility by cellulolytic enzymes.
Serving as an accelerant of lignocellulose hydrolysis, TS can also be degraded by the cellulolytic enzymes and release glucose while retaining stability, which reduces the cost of both the cellulolytic enzymes and the additive. As the glucose from the TS could be utilized by yeast, further efforts will investigate the mechanism of function and the application of TS in the production of ethanol by simultaneous saccharification and fermentation (SSF).
最近，人们对利用玉米芯残渣（CCR，木质素含量高达 45.1%）作为生物乙醇原料的兴趣日益浓厚。表面活性剂是最受欢迎的添加剂之一，旨在防止木质素对纤维素酶的抑制作用，从而提高水解效率。在这项研究中，研究了生物表面活性剂茶皂素（TS）对 CCR 酶水解的影响，以及纤维素酶与底物的结合行为。还检测了上清液的表面张力，以获取有关 TS 特性和稳定性的信息。
在低加载量的纤维素酶（7.0 FPU/g 纤维素和 10.5 BGU/g 纤维素）和 5% CCR 的条件下，水解 120 小时后葡萄糖浓度为 17.15mg/mL。TS 的最佳剂量为其临界胶束浓度（cmc，1.80mg/mL）。TS 可将葡萄糖产率从 34.29g/100g 干物质提高到 46.28g/100g 干物质。结果表明，TS 可以促进纤维素酶在底物上的吸附，并介导吸附酶的释放。同时，TS 提高了纤维素酶在水解循环后的回收效率，并防止了酶在剧烈搅拌过程中的失活。含有 TS 的 CCR 消化上清液的表面张力在水解过程中保持在 50.00mN/m。有趣的是，尽管生物表面活性剂 TS 可被纤维素酶消化，但它仍能维持上清液的表面张力。
作为木质纤维素水解的加速剂，TS 可以被纤维素酶降解，并在保持稳定性的同时释放葡萄糖，从而降低纤维素酶和添加剂的成本。由于 TS 产生的葡萄糖可以被酵母利用，因此将进一步研究 TS 在同步糖化发酵（SSF）生产乙醇中的功能机制和应用。
