Campbell Emily P, Kasler David R, Yousef Ahmed E
Department of Food Science and Technology, The Ohio State University, Columbus, OH 43210, USA.
Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
Foods. 2022 Jul 31;11(15):2290. doi: 10.3390/foods11152290.
Industrial production of paenibacillin, and similar rare antimicrobial peptides, is hampered by low productivity of the producing microorganisms and lack of efficient methods to recover these peptides from fermentor or bioreactor end products. Preliminary data showed that paenibacillin was preferentially partitioned in foam accumulated during growth of the producer, Paenibacillus polymyxa, in aerated liquid media. This research was initiated to improve the production and recovery of paenibacillin in bioreactors by maximizing partitioning of this antimicrobial agent in the collected foam. This was completed through harvesting foam continuously during paenibacillin production, using modified bioreactor, and optimizing bioreaction conditions through response surface methodology (RSM). During initial screening, the following factors were tested using 400 mL inoculated media in 2 L bioreactors: medium (tryptic soy broth, TSB, with or without added yeast extract), airflow (0 or 0.8 L/min; LPM), stir speed (300 or 500 revolution/min; RPM), incubation temperature (30 or 36 °C), and incubation time (16 or 24 h). Results showed that airflow, time, and stir speed had significant effects (p < 0.05) on paenibacillin recovery in the collected collapsed foam (foamate). These factors were varied together to follow the path of steepest assent to maximize paenibacillin concentration. Once the local maximum was found, RSM was completed with a central composite design to fine-tune the bioreaction parameters. The optimization experiments proved that the significant parameters and their optimal conditions for paenibacillin concentration in the foam were: incubation at 30 °C for 23 h with airflow of 0.95 LPM, and agitation speed of 450 RPM. These conditions increased paenibacillin concentration, predicted by RSM, from 16 µg/mL in bioreaction without foam collection to 743 µg/mL collected in foamate. The optimized conditions also almost doubled the yield of paenibacillin measured in the foam collected from a bioreaction run (12,674 µg/400 mL bioreaction) when compared to that obtained from a run without foam collection (6400 µg/400 mL bioreaction). Results of this study could improve the feasibility of commercial production and downstream processing of paenibacillin and similar novel antimicrobial peptides. Availability of such peptides will eventually help in protecting perishable products against pathogenic and spoilage bacteria.
类芽孢杆菌素以及类似的稀有抗菌肽的工业化生产受到生产微生物低生产率以及缺乏从发酵罐或生物反应器终产物中回收这些肽的有效方法的阻碍。初步数据表明，类芽孢杆菌素优先分配在产气荚膜梭菌在充气液体培养基中生长期间积累的泡沫中。本研究旨在通过使这种抗菌剂在收集的泡沫中最大程度地分配，来提高生物反应器中类芽孢杆菌素的生产和回收率。这是通过在类芽孢杆菌素生产过程中连续收集泡沫、使用改良的生物反应器以及通过响应面法（RSM）优化生物反应条件来完成的。在初步筛选期间，使用2 L生物反应器中的400 mL接种培养基测试了以下因素：培养基（胰蛋白胨大豆肉汤，TSB，添加或不添加酵母提取物）、气流（0或0.8 L/分钟；LPM）、搅拌速度（300或500转/分钟；RPM）、培养温度（30或36℃）和培养时间（16或24小时）。结果表明，气流、时间和搅拌速度对收集的塌陷泡沫（泡沫产物）中类芽孢杆菌素的回收率有显著影响（p < 0.05）。这些因素一起变化以遵循最陡上升路径，以最大化类芽孢杆菌素浓度。一旦找到局部最大值，就采用中心复合设计完成RSM，以微调生物反应参数。优化实验证明，泡沫中类芽孢杆菌素浓度的显著参数及其最佳条件为：在30℃下培养23小时，气流为0.95 LPM，搅拌速度为450 RPM。这些条件使RSM预测的类芽孢杆菌素浓度从无泡沫收集的生物反应中的16μg/mL增加到泡沫产物中收集的743μg/mL。与无泡沫收集的运行（6400μg/400 mL生物反应）相比，优化条件还使从生物反应运行中收集的泡沫中测得的类芽孢杆菌素产量几乎增加了一倍（12,674μg/400 mL生物反应）。本研究结果可以提高类芽孢杆菌素和类似新型抗菌肽的商业生产和下游加工的可行性。此类肽的可用性最终将有助于保护易腐产品免受致病和腐败细菌的侵害。
