Effect of Lactobacillus casei HDS-01 on the Quality Index and Bacterial Community Structure of Sauerkraut

Lactobacillus casei HDS-01, isolated from spent brine from sauerkraut, was added to construct a microbial ecosystem for sauerkraut fermentation. High performance liquid chromatography (HPLC), acid-base titration, high-throughput sequencing and real-time quantitative PCR were adopted in combination with traditional enzymatic analysis to investigate the dynamic changes of physicochemical properties and bacterial communities during sauerkraut fermentation. Meanwile, sensory quality and safety of the sauerkraut were evaluated. Results showed that the pH of fermented sauerkraut with L. casei HDS-01 decreased to 3.15±0.08 on the third day and the lactic acid bacteria count was (7.63±0.19) lg CFU/mL at the beginning of fermentation. The key enzyme activities of the lactic acid metabolic pathway were higher in all periods of L. casei HDS-01 fermented sauerkraut than in natural fermented sauerkraut (P<0.05). At the end of fermentation, the lactic acid, total acid and V_C contents were (7.88±0.38), (8.45±0.38) g/L and (445.02±10.53) mg/kg, respectively, and the nitrite content was (1.55±0.86) mg/kg. Sensory evaluation of sauerkraut samples showed that L. casei HDS-01 fermented sauerkraut was superior to naturally fermented sauerkraut in terms of clarity of fermentation broth, color, aroma, taste and crispness of sauerkraut. In addition, Lactobacillus remained consistently dominant in L. casei HDS-01 fermented sauerkraut (63.36% to 95.79%), reducing the abundance of pathogenic bacteria such as Enterobacter spp. (0.04% to 2.26%) and Pseudomonas spp. (0.28% to 25.84%), which regulated the diversity of flora and shortened the fermentation process. This study would have important practical significance for the development of strain resources and functional bacteria for fermentation.