Production of Propionate by a Sequential Fermentation-Biotransformation Process via l-Threonine.
Production of Propionate by a Sequential Fermentation-Biotransformation Process via l-Threonine.
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通过经由l-苏氨酸的连续发酵-生物转化工艺生产丙酸盐。
DOI：
10.1021/acs.jafc.1c05248
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发表时间：
2021-11
影响因子：
6.1
通讯作者：
Qingxuan Mu;Ya'nan Shi;Rongshan Li;Chao Ma;Y. Tao;Bo Yu
中科院分区：
文献类型：
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作者：
Qingxuan Mu;Ya'nan Shi;Rongshan Li;Chao Ma;Y. Tao;Bo Yu
生物基丙酸盐在食品添加剂行业受到广泛欢迎。目前丙酸菌厌氧工艺具有低滴度和长发酵时间的特点。本研究设计了一条以l-苏氨酸为原料生产丙酸盐的新路线。由l-苏氨酸脱胺得到的2-酮丁酸酯裂解成丙醛和CO2，然后氧化生成丙酸，丙酸被第一步脱胺放出的氨中和。这种不依赖辅酶a的途径，只有二氧化碳作为副产物，可以提高l-苏氨酸的丙酸生产效率和纯度。选择了2-酮丁酸脱羧关键酶，并对其表达进行了优化。利用乳球菌2-酮异戊酸脱羧酶改造的恶臭假单胞菌在24 h的间歇生物转化过程中，可从600 mM的L -苏氨酸中产生580 mM （43 g/L）的纯丙酸。此外，在进料批模式下，丙酸滴度为62 g/L，产率为1.07 g/L/h，摩尔产率为>0.98。最后，一种高效的顺序发酵-生物转化工艺被证明可以直接从含有l-苏氨酸的发酵液中生产丙酸盐，这进一步降低了成本，因为不需要提纯l-苏氨酸。
Bio-based propionate is widely welcome in the food additive industry. The current anaerobic process by Propionibacteria endures low titers and a long fermentation time. In this study, a new route for propionate production from l-threonine was designed. 2-Ketobutyrate, deaminated from l-threonine, is cleaved into propionaldehyde and CO2 and then be oxidized into propionic acid, which is neutralized by ammonia released from the first deamination step. This CoA-independent pathway with only CO2 as a byproduct boosts propionate production from l-threonine with high productivity and purity. The key enzyme for 2-ketobutyrate decarboxylation was selected, and its expression was optimized. The engineered Pseudomonas putida strain, harboring 2-ketoisovalerate decarboxylase from Lactococcus lactis could produce 580 mM (43 g/L) pure propionic acid from 600 mM l-threonine in 24 h in the batch biotransformation process. Furthermore, a high titer of 62 g/L propionic acid with a productivity of 1.07 g/L/h and a molar yield of >0.98 was achieved in the fed-batch pattern. Finally, an efficient sequential fermentation-biotransformation process was demonstrated to produce propionate directly from the fermentation broth containing l-threonine, which further reduces the costs since no l-threonine purification step is required.