Propionic acid (PA) is an important organic compound with extensive application in different industrial sectors and is currently produced by petrochemical processes. The production of PA by large-scale fermentation processes presents a bottleneck, particularly due to low volumetric productivity. In this context, the present work aimed to produce PA by a biochemical route from a hemicellulosic hydrolysate of sorghum bagasse using the strain Propionibacterium acidipropionici CIP 53164. Conditions were optimized to increase volumetric productivity and process efficiency. Initially, in simple batch fermentation, a final concentration of PA of 17.5 g⋅L⁻¹ was obtained. Next, fed batch operation with free cells was adopted to minimize substrate inhibition. Although a higher concentration of PA was achieved (38.0 g⋅L⁻¹), the response variables (Y_P/S = 0.409 g⋅g⁻¹ and Q_P = 0.198 g⋅L⁻¹⋅H⁻¹) were close to those of the simple batch experiment. Finally, the fermentability of the hemicellulosic hydrolysate was investigated in a sequential batch with immobilized cells. The PA concentration achieved a maximum of 35.3 g⋅L⁻¹ in the third cycle; moreover, the volumetric productivity was almost sixfold higher (1.17 g⋅L⁻¹⋅H⁻¹) in sequential batch than in simple batch fermentation. The results are highly promising, providing preliminary data for studies on scaling up the production of this organic acid.

中文翻译：

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细胞固定化和连续间歇操作提高高粱甘蔗渣半纤维素水解产物丙酸产量

丙酸 (PA) 是一种重要的有机化合物，广泛应用于不同的工业部门，目前由石油化工过程生产。通过大规模发酵工艺生产 PA 是一个瓶颈，特别是由于体积生产率低。在此背景下，本工作旨在使用菌株Propionibacterium acidipropionici CIP 53164从高粱甘蔗渣的半纤维素水解产物通过生化途径生产 PA。优化条件以提高体积生产率和工艺效率。最初，在简单的分批发酵中，PA 的最终浓度为 17.5 g⋅L ^-1获得了。接下来，采用游离细胞分批补料操作，以尽量减少底物抑制。尽管实现了更高浓度的 PA（38.0 g⋅L ^-1），但响应变量（Y _P/S = 0.409 g⋅g ^-1和Q _P = 0.198 g⋅L ^-1 ⋅H ^-1）接近那些简单的批处理实验。最后，半纤维素水解物的发酵能力在固定化细胞的连续批次中进行了研究。PA浓度在第三个循环中达到最大值35.3 g⋅L ^{-1 ；}此外，体积生产率几乎高出六倍（1.17 g⋅L ^-1 ⋅H ^-1) 在顺序分批中比在简单分批发酵中。结果非常有希望，为研究扩大这种有机酸的生产提供了初步数据。