Teke George M, Gakingo Godfrey K, Pott Robert W M
Department of Process Engineering, Stellenbosch University, South Africa.
Department of Process Engineering, Stellenbosch University, South Africa; Department of Chemical Engineering, Dedan Kimathi University of Technology, Kenya.
J Biotechnol. 2022 Dec 10;360:55-61. doi: 10.1016/j.jbiotec.2022.10.017. Epub 2022 Oct 29.
Fermentation technology is commonly used as a mature process to produce numerous products with the help of micro-organisms. However, these organisms are sometimes inhibited by the accumulation of these products or their by-products. One route to circumvent this is via extractive fermentation, which combines the fermentation process with extraction. To facilitate this, novel bioreactor designs are required, such as the semi-partition bioreactor (SPB) which has been recently proposed for in-situ extractive fermentation. The latter combines a fermentation and an extraction unit into a single vessel using a mixer-settler principle. Where the bioproduct is produced in the mixer and removed continuous in the settler. As the SPB functionality is a subject of interest, this study builds on demonstrating different process conditions in the production of a sample bioprocess (lactic acid (LA)) which is susceptible to product inhibition. The results showed a 34.5 g/L LA concentration was obtained in the pH-controlled condition. While LA production can suffer from product inhibition, neutralizing agents can be easily used to curb inhibitory problems, however, the LA fermentation is a simple (and well-studied) example, which can demonstrate an alternative route to avoiding product inhibition (for systems which cannot be rescued using pH control). Hence, to replicate a scenario of product inhibition, two different process conditions were investigated, no pH control with no extraction (non-integrated), and no pH control with integrated extractive fermentation. Key findings showed higher LA concentration in integrated (25.10 g/L) as compared to the non-integrated (14.94 g/L) case with improved yield (0.75 gg (integrated) versus 0.60 gg (non-integrated)) and overall productivity (0.35 gLh(integrated) versus 0.20 gLh(non-integrated)) likewise. This is the first demonstration of an SP bioreactor, and shows how the reactor can be applied to improve productivity. Based on these results, the SPB design can be applied to produce any product liable to product inhibition.
发酵技术是一种常用的成熟工艺，借助微生物生产多种产品。然而，这些微生物有时会受到这些产品或其副产品积累的抑制。一种规避此问题的途径是通过萃取发酵，即将发酵过程与萃取相结合。为实现这一点，需要新颖的生物反应器设计，比如最近提出的用于原位萃取发酵的半分隔生物反应器（SPB）。后者利用混合澄清器原理将发酵单元和萃取单元整合到一个容器中。生物产品在混合器中产生，并在澄清器中连续移除。由于SPB的功能是一个受关注的课题，本研究基于展示在生产易受产物抑制的样本生物过程（乳酸（LA））中的不同工艺条件展开。结果表明，在pH控制条件下获得了34.5 g/L的LA浓度。虽然LA生产可能会受到产物抑制，但中和剂可轻松用于解决抑制问题，然而，LA发酵是一个简单（且研究充分）的例子，它可以展示一种避免产物抑制的替代途径（对于无法通过pH控制解决的系统）。因此，为模拟产物抑制的情况，研究了两种不同的工艺条件，即无pH控制且无萃取（非整合），以及无pH控制且采用整合萃取发酵。关键发现表明，与非整合情况（14.94 g/L）相比，整合情况下（25.10 g/L）的LA浓度更高，产率（分别为0.75 gg（整合）和0.60 gg（非整合））和总体生产率（分别为0.35 g/L·h（整合）和0.20 g/L·h（非整合））同样有所提高。这是对SP生物反应器的首次展示，并表明该反应器可如何应用于提高生产率。基于这些结果，SPB设计可应用于生产任何易受产物抑制的产品。
