| Chinese traditional vinegar, which is mainly fermented by solid fermentation with natural inoculation, had better quality, but the production and scale of which is restricted. Modern industrial scale vinegar, which is fermented by pure acetic acid bacteria strains, had poor flavor. Acetic acid fermentation is associated with the complex microbial flora. Microbial species and flora structure of vinegar production play the vital role in quality and flavor. Fujian traditional monascus vinegar, which had a unique flavor, is one of the famous Chinese traditional vinegar, and has a semi-continuous liquid circular brewing process as following:red liquor is added into the vinegar sample of Fujian traditional monascus vinegar, a certain percentage of ripe Fujian traditional monascus vinegar is removed one year later, then the same volume of the red liquor is added into the Fujian traditional monascus vinegar again to keep the fermentation to continue annually. In this paper, different types of selective medium were used to isolate the functional strains from the Fujian traditional monascus vinegar, the isolated strains were identified preliminarily, and their abilities of acid-production were studied.Twelve strains without hydrolyzed zone of CaCO3 were isolated, and some of their physiological characters were used, including the Gram stain, catalase, amylase and glucose fermentation experiments. Their DNAs were extracted by using the SDS-Proteinase K method for 16S rDNA PCR. Their PCR productions were subjected to agarose-gel electrophoresis and sequenced. According to morphology, physiological and biochemical characteristics and 16S rDNA sequences, these strains were classified as Bacillus spp.. The strains YBG1, YBG8, YBG9, YBG10 and YBG11 were identified as Bacillus pumilus, strain YBG2, YBG3 and YBG7 were identified as Bacillus licheniformis, and strain YBG5 and YBG6 were identified as Bacillus amyloliquefaciens. From the growth curves of the twelve strains determined by OD-value method strain YBG 5 entered the logarithmic growth phase firstly, and had the maximum cell concentration in the stable phase.In order to enrich the major acid-producing strains responsible for the fermentation of Fujian traditional monascus vinegar, red liquor with high concentration of ethanol was added into the vinegar sample of Fujian traditional monascus vinegar with high concentration of acetic acid. Seven acid-producing strains, which had dissolving zones around colonies on the plates with high concentration of ethanol, were isolated from the samples of liquid circulation process of Fujian traditional monascus vinegar. According to morphology, physiological and biochemical characteristics and 16S rDNA sequences, these strains were classified as Gluconacetobacter spp.. The strains Y5052, Y5054, Y5072 and Y5092 were identified as Gluconacetobacter swingsii, and the strains Y5032, Y5033 and Y5071 were identified as Gluconacetobacter europaeus. The acid-producing capacities of these strains were determined, the acid-producing capacity of strain Y5052 was the lowest with the production being 15.0 g/L in 7 days, and strain Y5054 the highest with the production being 57.0 g/L in 7 days. This paper also studied the effects of different initial pH, ethanol concentration and speed on the acid-production ability of strain Y5054, and found that the optimum fermentation conditions for the strain were as following:the initial pH of the culture medium 5.5, the ethanol concentration 4%, speed at 200 r/min. Under optimum conditions strain Y5054 had the maximum acid production.In this paper, red liquor and monascus vinegar were mixed according to a certain proportion to simulate the red yeast fermentation process, and strain Y5054 was added to the mixture. Microbial concentration, ethanol concentration and total acid content in the fermentation broth were determined. Because the measuring time was short, the concentration of the microbial, ethanol concentration and the total acid content did not change significantly. |
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