Isolation And Identification Of Acetic Acid Bacteria From Traditional Cantonese-style Rice Vinegar And Fed-batch Fermentation To Produce Rice Vinegar

Rice wine and edible alcohol as raw materials, traditional Cantonese-style rice vinegar isproduced by surface static fermentation. The flavor of the products is good and well welcomedby the market. Bacteria in the fermentation tanks are constituted by the natural domesticated wildstrains more than10years. The production cycle of Cantonese-style rice vinegar is about40daysand the total acid is3.5g/100mL--4.5g/100mL with stable products. But Cantonese-style ricevinegar fermentation technique also has some shortcomings, such as long fermentation period,needs enormous area and low acid production. Currently there are few studies on its mainfermentation bacteria and research on the fermentation technique improvement.In this paper, the isolation and identification of the bacteria in Cantonese rice vinegar, theimprovement of the fermentation process were studied. The main contents including:(1)Isolation and identification of the main acid-producing bacteria;(2) The effect of fermentationmode, carbon source, nitrogen source, phosphate and ammonium salt on its acid production andthe optimization of the medium;(3) The impact of fed-batch fermentation on acid production ofCantonese-style rice vinegar and orthogonal optimization of fed-batch fermentation technique.The mainly conclusions are as follows:(1)8strains of acid bacteria were isolated and one highly effective acetic strain was selectedthrough purification and acid test. The acid production of this strain was4.40g/100mL for8days. And it was preliminary identified as Gluconacetobacter xylinus according to itsmorphology, physiological and biochemical characteristics and16S rDNA, which was named asRF4．(2) Acid production as index, results showed that the acid production of static culture mode andwave bed culture mode were4.40g/100mL and3.20g/100mL, static culture mode was muchhigher than cultivated with wave bed, the optimum concentration of alcohol, glucose, yeastextract, Na2HPO4,(NH4)2SO4are5%(v/v),7.0%(m/v),1.5%(m/v),0.7%(m/v),0.9%(m/v).Orthogonal test showed that the best ratio for medium is glucose3%(m/v), alcohol5%(v/v),yeast extract0.5%(m/v), Na2HPO40.9%(m/v) and (NH4)2SO40.5%(m/v).(3) The impact of fed-batch fermentation on acid production of Cantonese-style rice vinegar wasinvestigated. The main contents include the distribution of Gluconacetobacter xylinus cell numbers in the fermentation broth and in the bacterial cellulose membrane during thefermentation process, the acid production variation of single batch and fed-batch fermentation,the impact of fed-batch fermentation on acid production. The results showed that the cell numberin bacterial cellulose membrane is200times of that in the fermented liquid on the tenth day. Andfed-batch fermentation is advantageous in improving total acidity. The result of orthogonal testshows that the optimal conditions were: the sixth day began to add, add every2days one time,every time adds2%(volume of alcohol/volume of fermented liquid) and for3times. Under thiscondition, the total acidity was at7.29g/100mL,61.3%higher than4.52g/100mL by optimizedfermentation medium and much higher than traditional technique which is range from3.5--4.5g/100mL.