Rapid manufacture and quality evaluation of long-term fermented kimchi (mukeunji) using Lactobacillus sakei SC1

Integrated Phenotypic-Genotypic Analysis of Latilactobacillus sakei from Different Niches

Increasing attention has been paid to the potential probiotic effects of Latilactobacillus sakei. To explore the genetic diversity of L. sakei, 14 strains isolated from different niches (feces, fermented kimchi, and meat products) and 54 published strains were compared and analyzed. The results showed that the average genome size and GC content of L. sakei were 1.98 Mb and 41.22%, respectively. Its core genome mainly encodes translation and transcription, amino acid synthesis, glucose metabolism, and defense functions. L. sakei has open pan-genomic characteristics, and its pan-gene curve shows an upward trend. The genetic diversity of L. sakei is mainly reflected in carbohydrate utilization, antibiotic tolerance, and immune/competition-related factors, such as clustering regular interval short palindromic repeat sequence (CRISPR)-Cas. The CRISPR system is mainly IIA type, and a few are IIC types. This work provides a basis for the study of this species.

Correlation between microbiota and flavours in fermentation of Chinese Sichuan Paocai

Sichuan Paocai (SCP), a traditional fermentationed food, possesses unique flavours driven by various microbiota in fermentation ecosystems. However, the association between these microbiota and flavours is poorly understood. Here, we measured the structural dynamics of the microbial diversity and flavour compounds during SCP fermentation (0-7 days) using high-throughput sequencing and flavour analyses. Firstly, a total of 90 bacteria and 135 fungi were identified. The results showed that fermentation process was initiated by environmental microorganisms, such as Micrococcaceae, followed by a heterolactic fermentation phase dominated by Leuconostocaceae, and finally succeeded by homolactic fermentation led by Lactobacillaceae. Secondly, 6 organic acids, 12 amino acids and 86 volatile flavours were detected. The fermentation process was divided into 4 stages based on flavours: Day 0; Days 1-3; Days 4-6; and Day 7. Analysis of the correlation between microbiota and flavours indicated that bacteria contributed more to flavours formation than did fungi, and Lactobacillus, Leuconostoc, Achromobacter and Pediococcus were closely correlated with flavours. This study provides a systematic method for understanding the characteristics of fermented foods and useful guidelines for screening of strains that produce desirable flavours and functional substances.

Use of Psychrotolerant Lactic Acid Bacteria (Lactobacillus spp. and Leuconostoc spp.) Isolated from Chinese Traditional Paocai for the Quality Improvement of Paocai Products

To improve the quality of Chinese traditional Paocai, two psychrotolerant lactic acid bacteria (LAB) strains were isolated from Paocai, and the quality of Chinese Paocai product using these two strains as starter cultures was compared to a control sample fermented with aged brine at 10 °C. The results suggested that the physicochemical and sensory features of Paocai fermented with psychrotolerant LAB were more suitable for industrial applications. The nitrite content of Paocai fermented with psychrotolerant LAB was 1 mg/kg, which was significantly lower than that of the control Paocai (P < 0.05). Low-temperature fermentation with the starter cultures of psychrotolerant LAB could effectively prevent overacidity and over-ripening of the Paocai products. Additionally, Paocai fermented with psychrotolerant LAB harbored relatively simple microbial flora as revealed by polymerase chain reaction-denaturing gradient gel electrophoresis. This study provides a basis for improving the quality of Chinese traditional Paocai and the large-scale production of low-temperature Chinese traditional Paocai products.