Abstract: Three strains of lactobacillus were isolated and identified from fermented liquid of pickle after isolation and identification. They were identified as Lactobacillus brevis, Lactobacillus plantarum and Lactobacillus casei. Then these lactic acid bacteria were used to directly ferment Pyropia yezoensis with four different ratios, and some physical and chemical changes in the fermentation process was discussed. The results showed that all four kind of mixed lactobacillus fermentation broth had similar pH decline trends, from 4.51 to 2.90; 1∶1∶2 (V∶V∶V) mixed lactobacillus fermentation broth had the strongest acid production capacity, and at the end point of fermentation, the total acid content was 13.75 g/L, which was 6 times of the beginning; the total sugar content of 1∶1∶2 mixed lactobacillus fermentation broth was from the initial 29.95 g/L to 18.97 g/L at the fermentation end point; the minimum peak of nitrite content of 1∶1∶2 mixed lactobacillus fermentation broth was 3.75 mg/kg; the higher amino acid content occurred in 1∶1∶1 mixed lactobacillus fermentation broth, with the maximum value of 58.16 μmol/mL; the 1∶1∶3 mixed lactobacillus fermentation broth had the largest decrease of protein content.

Key words: lactobacillus, isolation and identification, Porphyra yezoensis, fermentation, physical and chemical factors