Zhuang Wei, Liu Xiaojing, Yang Jing, Wu Jinglan, Zhou Jingwei, Chen Yong, Liu Dong, Ying Hanjie
State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, No. 5, Xinmofan Road, Nanjing, 210009, China.
College of Biotechnology and Pharmaceutical Engineering, National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, No. 30, Puzhu South Road, Nanjing, 211816, China.
Microb Biotechnol. 2017 Mar;10(2):502-512. doi: 10.1111/1751-7915.12557. Epub 2017 Jan 23.
Immobilized fermentation has several advantages over traditional suspended fermentation, including simple and continuous operation, improved fermentation performance and reduced cost. Carrier is the most adjustable element among three elements of immobilized fermentation, including carrier, bacteria and environment. In this study, we characterized carrier roughness and surface properties of four types of natural fibres, including linen, cotton, bamboo fibre and silk, to assess their effects on cell immobilization, fermentation performance and stability. Linen with higher specific surface area and roughness could adsorb more bacteria during immobilized fermentation, thereby improving fermentation performance; thus, linen was selected as a suitable carrier and was applied for acetone-butanol-ethanol (ABE) fermentation. To further improve fermentation performance, we also found that microbes of Clostridium acetobutylicum were negatively charged surfaces during fermentation. Therefore, we then modified linen with polyetherimide (PEI) and steric acid (SA) to increase surface positive charge and improve surface property. During ABE fermentation, the adhesion between modified linen and bacteria was increased, adsorption was increased about twofold compared with that of unmodified linen, and butanol productivity was increased 8.16% and 6.80% with PEI- and SA-modified linen as carriers respectively.
固定化发酵相对于传统悬浮发酵具有多个优点，包括操作简单且连续、发酵性能提高以及成本降低。载体是固定化发酵三个要素（载体、细菌和环境）中最具可调节性的要素。在本研究中，我们对包括亚麻、棉花、竹纤维和丝绸在内的四种天然纤维的载体粗糙度和表面性质进行了表征，以评估它们对细胞固定化、发酵性能和稳定性的影响。具有较高比表面积和粗糙度的亚麻在固定化发酵过程中能够吸附更多细菌，从而提高发酵性能；因此，亚麻被选为合适的载体并应用于丙酮 - 丁醇 - 乙醇（ABE）发酵。为了进一步提高发酵性能，我们还发现丙酮丁醇梭菌的微生物在发酵过程中表面带负电荷。因此，我们随后用聚醚酰亚胺（PEI）和硬脂酸（SA）对亚麻进行改性，以增加表面正电荷并改善表面性质。在ABE发酵过程中，改性亚麻与细菌之间的粘附力增加，吸附量相比未改性亚麻增加了约两倍，以PEI改性亚麻和SA改性亚麻为载体时，丁醇生产率分别提高了8.16%和6.80%。
