背景:从可再生原料中发酵的丙酸具有较低的体积生产率和最终产物浓度,这限制了微生物途径的工业可行性。高细胞密度发酵技术克服了这些局限性。这里,丙酸(PA)从葡萄糖和粗甘油/葡萄糖混合物的生产使用酸丙酸杆菌进行评估,在具有细胞再循环的高细胞密度(HCD)分批发酵中。农业工业副产品,热处理过的马铃薯汁,用作N源。
结果:连续9个批次使用40g/L葡萄糖,每批次平均产生18.76±1.34g/L的PA(0.59gPA/gGlu),最大速率为1.15gPA/L。h,最大生物量为39.89gCDW/L获得琥珀酸(SA)和乙酸(AA)作为主要副产物,并且PA:SA:AA的质量比为100:23:25。当粗甘油/葡萄糖混合物(60g/L:30g/L)用于6个连续批次的细胞循环时,在0.35g/L的最大速率下,每批平均获得35.36±2.17g/L的PA(0.51gPA/gC源)。h,达到最大生物量浓度12.66gCDW/L。PA:SA:AA的质量比为100:29:3。在培养基中进一步添加0.75mg/L生物素作为补充剂,细胞生长达到21.89gCDW/L,PA生产率为0.48g/Lh,而且AA浓度也增加了一倍。
结论:这是报告的来自甘油/葡萄糖共发酵的最高生产率,其中大多数培养基组分包含工业副产物(粗甘油和HTPJ)。具有细胞再循环的HCD分批发酵是生物过程工业化的有希望的方法。
BACKGROUND: Propionic acid fermentation from renewable feedstock suffers from low volumetric productivity and final product concentration, which limits the industrial feasibility of the microbial route. High cell density fermentation techniques overcome these limitations. Here, propionic acid (PA) production from glucose and a crude glycerol/glucose mixture was evaluated using Acidipropionibacterium acidipropionici, in high cell density (HCD) batch fermentations with cell recycle. The agro-industrial by-product, heat-treated potato juice, was used as N-source.
RESULTS: Using 40 g/L glucose for nine consecutive batches yielded an average of 18.76 ± 1.34 g/L of PA per batch (0.59 gPA/gGlu) at a maximum rate of 1.15 gPA/L.h, and a maximum biomass of 39.89 gCDW/L. Succinic acid (SA) and acetic acid (AA) were obtained as major by-products and the mass ratio of PA:SA:AA was 100:23:25. When a crude glycerol/glucose mixture (60 g/L:30 g/L) was used for 6 consecutive batches with cell recycle, an average of 35.36 ± 2.17 g/L of PA was obtained per batch (0.51 gPA/gC-source) at a maximum rate of 0.35 g/L.h, and reaching a maximum biomass concentration of 12.66 gCDW/L. The PA:SA:AA mass ratio was 100:29:3. Further addition of 0.75 mg/L biotin as a supplement to the culture medium enhanced the cell growth reaching 21.89 gCDW/L, and PA productivity to 0.48 g/L.h, but also doubled AA concentration.
CONCLUSIONS: This is the highest reported productivity from glycerol/glucose co-fermentation where majority of the culture medium components comprised industrial by-products (crude glycerol and HTPJ). HCD batch fermentations with cell recycling are promising approaches towards industrialization of the bioprocess.