Study On Breeding And Characteristics Of Fine Acetic Acid Bacteria For Brewing Fruit Vinegar

Fruit vinegar has a long history of development in China.It is mainly obtained by fermentation of various fruits with acetic acid bacteria and other microorganisms after yeast fermentation.It is rich in acetic acid,flavonoids and other active substances,which can play a role in improving immunity,anti-oxidation and health care.China is a large producer of fruits and vegetables,with a variety of fruit species,there is still a gap between China and European and American countries in the brewing technology of fruits and vegetables and the development of excellent strains for brewing.This paper mainly studied four aspects: screening of acetic acid bacteria for fruit vinegar brewing,optimization of fermentation conditions,improvement of acetic acid bacteria induced by ARTP and brewing of Nanfeng tangerine vinegar.The main research results are as follows:Taking Nanfeng Tangerine aged fruit vinegar as a sample,the predominant strains NF-171 and NF-172 were isolated by plate separation and qualitative screening.Based on strain morphology and 16 S r DNA sequence analysis,it was identified as Acetobacter pasteurianus.The shake flask fermentation results showed that the strains A.pasteurianus NF-171 and NF-172 can both stably produce acetic acid with a concentration of 36.13 g/L and 33.63 g/L,and both can tolerate high temperature of 42 ℃ and 13% ethanol.Among them,the strain NF-171 is more resistant to high temperature than the strains NF-172,at 40℃ can produce acetic acid31.65 g/L;but the strain NF-172 has better tolerance to ethanol,Which can produce58.65 g/L of acetic acid at 13% ethanol concentration.Taking the acid production of strain NF-171 as an evaluation index,the optimal fermentation process parameters for fruit vinegar obtained through the single factor and response surface optimization fermentation process are: initial ethanol concentration 4%,temperature 31℃,When the initial acetic acid concentration was 0.72% and the inoculation amount was 10%,the theoretical acetic acid content of the strain was 36.8 g/L,the actual acetic acid content was 36.5 g/L,and the theoretical conversion rate of ethanol was 69.65%.Taking strain NF-171 as the object,random mutation was carried out by using atmospheric and room temperature plasma(ARTP)mutagenesis technology,and a positive mutant strain with slightly increased acid production was selected,labeledNF-171.60,at 4% of the initial ethanol conditions,the acid yield of the strain can reach 35.7 g/L,which is only slightly higher than the control strain NF-171(34.8 g/L).The strain NF-171.60 was further subjected to ARTP mutagenesis,and then a high-yield strain YNF-171.24 was screened.Under the condition of 31℃ and 10%initial ethanol,the acid yield could reach 79.2 g/L,which was comparable to that of the control strain NF-171.60(48.75 g/L),the yield of acetic acid increased by about62.46%.Studies on the production of fruit vinegar by fermentation of Nanfeng Tangerine Fruit Wine(5% alcohol content)with the original strain NF-171 and the mutant strain YNF-171.24 were carried out.The results showed that the acid production of strains NF-171 and YNF-171.24 was 45.15 g/L and 48.45 g/L,respectively.A 5L fermentation tank was used for small-scale fermentation of Nanfeng Tangerine Fruit Vinegar.It was found that under aeration of 2 L/min,the acetic acid yield of strain YNF-171.24 was 42.1 g/L.The total acid concentration of Nanfeng Tangerine Fruit Vinegar was approximately 51.6 g/L,which is consistent with the estimated experimental results.This can provide a certain theoretical basis for the fermentation of Nanfeng Tangerine Fruit Vinegar.