Lei Du,Kum-Song Ro,Yiji Zhang,Ya-Jie Tang,Wanbang Li,Jingli Xie,Dongzhi Wei
The capability of Lactiplantibacillus plantarum X7021, which was isolated from the stinky tofu brine and completely sequenced, in soymilk fermentation was evaluated based on the study of growth, acidification, viscosity generation, purine ingestion and soy isoflavones glycosides bioconversion, as well as the volatile compounds production of the strain during soymilk fermentation. The yoghurt starter culture was used as a comparison and co-starter. Rapid growth of the strain increasing from 7.0–8.7 lg CFU/mL and pH dropping from 6.6 to 5.3 happened during the first 8 h, accompanying with the viscosity of soymilk raised to 1391 mPa⋅s. Three major purines, guanine, hypoxanthine and xanthine, in soymilk were significantly decreased 38.8 %, 26.1 % and 65.3 % respectively, due to the abundant purine permease systems of the strain. Furthermore, total isoflavones were reduced (147.6 mg/L → 57.1 mg/L) with an increase of aglycone contents and the percentage composition of aglycone increased from 2.7 %–67.5 % after fermentation. Thirty-three volatile compounds were detected in the fermented soymilk versus 12 volatile compounds in soymilk. L. plantarum X7021 displayed higher degradation of the main beany flavor compounds, hexanal, 1-octen-3-ol and 2-pentyl furan than yoghurt starter. Besides, significant increase of volatile compounds, acetate, acetoin and 2,3-butanedione were observed because of the complete pyruvate metabolic pathway of the strain.
Lactiplantibacillus plantarum X7021 is a novel strain originated from the brine of stinky tofu. In order to investigate the application potential of the strain in food industry, the genomic characteristics as well as some metabolic features were studied using comparison genomics and transcriptional assay. The complete genome of X7021includes a 3,407,054 bp chromosome with 3259 protein coding sequences, and 6 plasmids. L. plantarum strains, WCFS1, JDM1, and ST-III were selected for comparative genomic analysis. Results revealed that X7021 is safe for the application in foods with less antibiotic resistance and virulence genes. The strain has 25 complete phosphotransferase system transporters and strong proteolytic system for its adaptability to various foodstuffs. The strain containes a complete purine metabolic pathway incorporating 4 permeases, resulting in the reductions of 38.9% guanine, 26.1% hypoxanthine and 70.2% xanthine during the soymilk fermentation. Soy isoflavone glycosides could be converted to corresponding aglycones by two β-glucosidases. The strain could grow in 700 mg/L nitrite and entirely degrade 100 mg/L nitrite during 24 h based on highly active nitrite transporter and nitrite reductase. Accordingly, the results suggest that L. plantarum X7021 is a prospect starter candidate for the fermentation of plant foodstuffs.
危险品化学品经营许可证（带存储）