Biological Characteristics Of Phenyllactic Acid-producing Lactic Acid Bacteria And Its Application In Vinegar Production

Vinegar is not only a condiment,but also a health food,which contains a variety of bioactive ingredients,such as tetramine,chlorogenic acid and so on.Phenyllactic acid（PLA）is a newly detected substance in vinegar.It is a natural metabolite of lactic acid bacteria,which has the functions of inhibiting intestinal microorganisms and protecting cardiovascular health.In order to improve the health effect of vinegar,it is a good method to strengthen the active components by changing raw materials or using microbial metabolism.Lactic acid bacteria are the main microorganism in vinegar fermentation,which can produce phenyllactic acid,lactic acid and other nutrients.By adding lactic acid bacteria to bioaugmentation vinegar fermentation,the contents of phenyllactic acid,lactic acid and other substances in vinegar can be increased effectively,and the added value of vinegar can be increased.In this study,15 lactic acid bacteria from vinegar fermented grains were identified and their ability to produce phenyllactic acid was analyzed,and representative lactic acid bacteria were selected to study their biological characteristics.Its application in solid fermentation vinegar and liquid fermentation black rice vinegar was studied.The results are as follows:1.Biological characteristics of lactic acid bacteria producing phenyllactic acid15 strains of lactic acid bacteria were identified as 1 strain of Lactobacillus plantarum,8 strains of Lactobacillus helveticus,and 6 strains of Lactobacillus paracasei.The yield of phenyllactic acid was 23.74-132.77 mg/L in MRS broth for 48 h.Taking Lactobacillus plantarum LP,Lactobacillus helveticus L9 and Lactobacillus paracasei LE as representatives to study the biological characteristics,the three strains can grow and produce phenyllactic acid at 20～45℃.It could tolerate up to 10%ethanol and 1%acetic acid.The three strains had good antioxidant activity and H₂O₂ tolerance.The survival rate ranged from 86.61%to 95.61%after 3 hours of bile salt treatment,and 29.11%to 70.36%after 11 hours of gastrointestinal fluid treatment.2.Preliminary application of lactic acid bacteria producing phenyllactic acid in solid-state fermentation vinegarAccording to the production process of Zhenjiang vinegar,three lactic acid bacteria were applied in solid-state fermentation.During the fermentation process,the water content was kept at 62-66%,the p H value stabilized at 3.7 after a rapid decrease.The temperature remained stable after reaching 45℃on the 5th day,and began to decrease to 39℃on the12th day.Lactic acid bacteria significantly increased the content of the main components of vinegar（calculated by 100 g dried vinegar Pei）,and L9 had the best effect,the total acid content was 12.34 g,phenyllactic acid 78.95 mg,lactic acid 3.46 g,acetic acid 8.18 g,succinic acid 366.99 mg,reducing sugar 5.21 g,amino acid nitrogen 1.01 g and 60 kinds of volatile flavor substances.3.Preliminary application of lactic acid bacteria producing phenyllactic acid in liquid-state fermentation black rice vinegarThe interaction between LP,L9,LE and Acetobacter pasteurianus AS1.41 and Gluconacetobacter FBFS97 was investigated by additive model method and simulated in situ and ectopic culture.It was found that L9 and AS 1.41 had a synergistic effect to increase the fermentation rate and phenyllactic acid production,which was an inhibitory effect among the other strains.It was inoculated and fermented in two-by-two combinations to brew black rice vinegar.The quality of black rice vinegar was judged according to indicators such as total acid,phenyllactic acid,and volatile flavor,which was consistent with the interaction results between strains.The quality of black rice vinegar co-fermented with L9 and AS 1.41 was the best,the total acid content of vinegar was 7.40 g/100m L,p H3.38,phenyllactic acid 41.83 mg/L,lactic acid 1.83 g/100m L,acetic acid 5.12 g/100m L,reducing sugar 22.55 g/L,amino acid nitrogen 2.23 g/L,anthocyanin 1.40 mg/L,and 74kinds of volatile flavor substances.The three strains of lactic acid bacteria had good biological characteristics,and the contents of lactic acid and phenyllactic acid in solid fermented vinegar and liquid fermented black rice vinegar could be increased by bioaugmentation,and the added value of vinegar can be increased,the quality of vinegar could be improved.