Propionic acid (PA) production from agro-industrial residues using propionibacteria has gained interest as an alternative to fossil-based process. Microbial production is however characterized by product inhibition, lowering the product titers and productivity. In this study, Propionibacterium acidipropionici DSMZ4900 was subjected to adaptive evolution to tolerate higher acid concentrations. The strain adapted to growth in medium spiked with 20 g/L PA exhibited improved product titer (16.8 vs 8.72 g/L) and productivity (0.52 vs 0.17 g/L·h) with glycerol as carbon source in batch fermentations. It was immobilized on polyethyleneimine coated recycled glass beads Poraver® and used for fermentations in recycle batch mode with increasing glycerol concentration and decreasing pH, respectively. Doubling yeast extract concentration raised PA yield and productivity by >1.5 fold. Glycerol at 100 g/L was completely consumed to give ∼58 g/L PA at yield of 0.64 mol/mol and productivity of 0.28 g/L·h at pH 6.5. Decreasing fermentation pH to 5.0 increased PA productivity to 0.23 g/L·h from 0.14 g/L·h at pH 6.0 with 20 g/L glycerol, while immobilized cells exhibited no growth. The study shows combination of adaptive evolution and immobilization of cells to result in a robust system for PA fermentation at high glycerol concentration and lower pH.

使用丙酸杆菌从农业工业残留物中生产丙酸 (PA) 作为基于化石的工艺的替代方法引起了人们的兴趣。然而，微生物生产的特征在于产物抑制，降低产物滴度和生产率。在本研究中，酸丙酸丙酸杆菌DSMZ4900 经过适应性进化以耐受更高的酸浓度。适应在掺有 20 g/L PA 的培养基中生长的菌株在分批发酵中以甘油为碳源表现出提高的产品效价（16.8 对 8.72 g/L）和生产力（0.52 对 0.17 g/L·h）。它被固定在聚乙烯亚胺涂层的回收玻璃珠 Poraver® 上，并分别用于在循环批次模式下增加甘油浓度和降低 pH 值的发酵。酵母提取物浓度加倍可将 PA 产量和生产力提高 1.5 倍以上。100 g/L 的甘油被完全消耗，以 0.64 mol/mol 的产率和 0.28 g/L·h 的生产率在 pH 6.5 下得到约 58 g/L 的 PA。将发酵 pH 值降低至 5.0，将 PA 生产率从 pH 6.0 和 20 g/L 甘油时的 0.14 g/L·h 提高至 0.23 g/L·h，而固定化细胞则没有生长。该研究表明，适应性进化和细胞固定相结合，可以在高甘油浓度和低 pH 值下形成一个强大的 PA 发酵系统。