Abstract

Propionic acid, a widely used food preservative and intermediate in the manufacture of various chemicals, is currently produced from petroleum-based chemicals, raising concerns about its long-term sustainability. A key way to make propionic acid more sustainable is through fermentation of low-cost renewable and inedible sugar sources, such as lignocellulosic biomass. To this end, we utilized the cellulosic hydrolysate of sweet sorghum bagasse (SSB), a residue from a promising biomass source that can be cultivated around the world, for fermentative propionic acid production using Propionibacterium freudenreichii. In serum bottles, SSB hydrolysate supported a higher propionic acid yield than glucose (0.51 vs. 0.44 g/g, respectively), which can be attributed to the presence of additional nutrients in the hydrolysate enhancing propionic acid biosynthesis and the pH buffering capacity of the hydrolysate. Additionally, SSB hydrolysate supported better cell growth kinetics and higher tolerance to product inhibition by P. freudenreichii. The yield was further improved by co-fermenting glycerol, a renewable byproduct of the biodiesel industry, reaching up to 0.59 g/g, whereas volumetric productivity was enhanced by running the fermentation with high cell density inoculum. In the bioreactor, although the yield was slightly lower than in serum bottles (0.45 g/g), higher final concentration and overall productivity of propionic acid were achieved. Compared to glucose (this study) and hydrolysates from other biomass species (literature), use of SSB hydrolysate as a renewable glucose source resulted in comparable or even higher propionic acid yields.

Key points

• Propionic acid yield and cell growth were higher in SSB hydrolysate than glucose.

• The yield was enhanced by co-fermenting SSB hydrolysate and glycerol.

• The productivity was enhanced under high cell density fermentation conditions.

• SSB hydrolysate is equivalent or superior to other reported hydrolysates.

中文翻译：

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使用甜高粱甘蔗渣水解物由弗氏丙酸杆菌生产丙酸

摘要

丙酸是一种广泛用于食品防腐剂和各种化学品生产的中间体，目前是由石油基化学品生产的，引起了人们对其长期可持续性的担忧。使丙酸更具可持续性的关键方法是发酵低成本的可再生和不可食用的糖源，例如木质纤维素生物质。为此，我们利用甜高粱甘蔗渣（SSB）的纤维素水解物（一种可以在世界范围内种植的有前途的生物质来源中的残渣）利用弗氏丙酸杆菌进行发酵丙酸生产。在血清瓶中，SSB水解产物支持的丙酸收率高于葡萄糖（分别为0.51对0.44 g / g），这可以归因于水解产物中存在其他营养物质，从而增强了丙酸的生物合成和pH缓冲能力。水解物。另外，SSB水解产物支持更好的细胞生长动力学和对弗氏疟原虫产物抑制的更高耐受性。通过共发酵生物柴油行业的一种可再生副产物甘油，产量可进一步提高，最高可达0.59 g / g，而通过在高细胞密度接种物中进行发酵，可以提高容积生产率。在生物反应器中，尽管产量略低于血清瓶中的产量（0.45 g / g），但实现了更高的丙酸最终浓度和整体生产率。与葡萄糖（本研究）和其他生物质物种的水解产物（文献）相比，SSB水解产物作为可再生葡萄糖来源的使用可产生甚至更高的丙酸收率。

关键点

• SSB水解产物的丙酸产率和细胞生长高于葡萄糖。

•通过SSB水解产物和甘油的共同发酵提高了产量。

•在高细胞密度发酵条件下提高了生产率。

• SSB水解产物与其他报道的水解产物相当或更高。