PCR-based denaturing gradient gel electrophoresis and identification of the microbial consortium present in kimchi treated with high pressure

Abstract

High static pressure is thought to be the promising technique to control fermentation. The effect of high pressure treatment on the composition of microbial flora during kimchi fermentation was examined using denaturing gradient gel electrophoresis of PCR-amplified DNA followed by nucleotide sequencing of the amplicons. Eleven lactic acid bacteria (LAB) strains, including Lactobacillus, Leuconostoc and Weissella species, were isolated from kimchi. During the 60-day fermentation period, a two-stage decrease of pH to 3.9 was observed. The cell concentration of LAB reached the maximum on the 15th day, and was maintained at 3.2×108 cfu/ml thereafter. Among LAB, Lactobacillus sakei was consistently observed, and Lactobacillus plantarum was observed after the 21st day. The cell concentration of yeasts reached the maximum of 1.4×108 cfu/ml on the 15th day and decreased to an undetectable level after the 27th day. Kazachstania servazzii was overwhelmingly dominant. When 200MPa high pressure treatment was applied for 60 min to the kimch on the 21st day, further decrease in pH was not observed. Cell concentrations of LAB and yeasts were suddenly reduced to 8.3×10 5 cfu/ml and an undetectable level, and recovered gradually and rapidly, respectively. Apparent difference in the microbial flora between the pressure-free and -treated samples were not observed. Addition of L. sakei and K. servazzii at the start of fermentation did not produce an apparent effect.