Production Of Vinegar By Acetic Acid Bacteria Biotransformation Using Edible Alcohol As Feedstock

Vinegar is a traditional oriental grain condiment with a sour taste and distinct fragrance,which are used in a wide range of food production process,fish processing industry,home cleaning and air purification.Investigation shows that the annual per-capita consumption of vinegar reaches about 2.3 kilograms.It is essential to develop an efficient and safe way to produce vinegar.Vinegar production by acetic acid bacteria?AAB?using edible alcohol as feedstock is a new technology,which have various advantages such as high efficiency,short producing cycle and rich flavor of the production.In this work,the process of production of wine vinegar from edible alcohol by AAB.WUST-01 biotransformation was investigated.We hope to develop a novel vinegar producing technique.First,the strain was identified by morphological observation,physiological-biochemical characteristic and molecularbiology identification.The result shows that,the strain was one of the species of Acetobacter pasteurianus.Then the medium for starting-up phase culture and fermentation phase were optimized separately.The optimal composition of starting-up stage for microbial growth is glucose 5.1 g/L,yeast extract 26.2 g/L,and ethanol 11.9 mL/L respectively.The fermentation phase follows the starting-up phase,which is mainly to produce vinegar.The optimal composition of ethanol in fermentation is 50 mL/L.At this condition,the total acid reached 45.0 g/L with a yield of 84.6%.Then,the repeated batch fermentation with part segmentation and continuous flow feed fermentation processes were respectively conducted in a 5 L mechanical agitation tank fermentor.The optimal discharge volume in repeated batch fermentation was 50%of total working volume.With this discharge rate,the fermentation cycle is 12 h,the total acid could reached to 77.3 g/L with a yield of70.0%.The total acid just 72.9 g/L in flow feed fermentation.Comprehensive analysis,AAB.WUST-01 has a potential application for the industrial fermentation,especially in repeated batch fermentation with 50%discharge volume of total working volume.Finally,the metabolic mechanism in acetic fermentation was preliminarily investigated.The coenzyme Q,alcohol dehydrogenase?ADH?and aldehyde dehydrogenase?ALDH?were studied.It was revealed that the main type of coenzyme Q in AAB.WUST-01 was Q₁₀.Then,we tried to regulate the content of coenzyme Q in AAB.WUST-01 by p-hydroxybenzoic acid and L-phenylalanine.The result shows that,the content of coenzyme Q was increased 10.1%and 11.55%respectively.The total acid were rised 8.1%with the addition of p-hydroxybenzoic acid.Also,the activity of ADH and ALDH was regulated by Fe²⁺and the pueraria flower extract?PFE?to enforce the vinegar synthesis.The ADH and ALDH activity have raised,and the total acid increased 16.3%with the addition of Fe²⁺.The ADH activity increased35.1%while the ALDH had no obvious change with the addition of PFE,and the total acid increased 13.2%.The results demonstrate that,regulators can affect the metabolism of enzymes and enforce the vinegar synthesis to a certain degree.This work provides a direction for wine vinegar's production,and also provides a basis for the innovation of vinegar production technology.