School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, PR China.
J Biotechnol. 2012 Dec 31;162(2-3):202-9. doi: 10.1016/j.jbiotec.2012.10.004. Epub 2012 Oct 16.
Microbial fermentation of intracellular product is usually limited by high intracellular product concentration inhibition and complex downstream product processing. Perstractive fermentation of intracellular Monascus pigments in the nonionic surfactant Triton X-100 aqueous solution was studied in the present work, in which the intracellular product was exported from the intracellular to the extracellular aqueous solution and consecutively extracted into the nonionic surfactant micelles. After the second stage perstractive fermentation in the two-stage operation mode, biomass increased from 5 to 24 g/l DCW. The corresponding extracellular concentrations of yellow, orange, and red pigments were 60, 49 and 26 AU. The increase of cell density and the final pigment concentration were difficult to occur in a conventional aqueous medium using the two-stage fermentation. This positive effect of perstractive fermentation was ascribed to low intracellular pigment density, which eliminated the product inhibition and prevented the product from further degradation. The high efficiency of perstractive fermentation was further confirmed by fed-batch operation mode, in which the final biomass reached 28 g/l DCW and the corresponding extracellular concentrations of yellow, orange, and red pigments were 130, 84 and 47 AU.
细胞内产物的微生物发酵通常受到高细胞内产物浓度抑制和复杂的下游产物加工的限制。本研究在非离子表面活性剂 Triton X-100 水溶液中对细胞内红曲色素进行了萃取发酵，其中细胞内产物从细胞内转移到细胞外水溶液中，并连续萃取到非离子表面活性剂胶束中。在两阶段操作模式下进行二次萃取发酵后，生物量从 5 增加到 24 g/l DCW。相应的黄色、橙色和红色色素的胞外浓度分别为 60、49 和 26 AU。在传统的水相介质中，采用两阶段发酵，细胞密度的增加和最终色素浓度的增加都很困难。萃取发酵的这种积极作用归因于低细胞内色素密度，消除了产物抑制并防止产物进一步降解。补料分批操作模式进一步证实了萃取发酵的高效率，最终生物量达到 28 g/l DCW，相应的黄色、橙色和红色色素的胞外浓度分别为 130、84 和 47 AU。
