Improving acetic acid production of Acetobacter pasteurianus AC2005 in hawthorn vinegar fermentation by using beer for seed culture

Metabolite Profile and Immunomodulatory Properties of Bellflower Root Vinegar Produced Using Acetobacter pasteurianus A11-2

Fermented vinegar is prepared from grains and medicinal plants. Here, we produced vinegar from peeled and unpeeled roots of bellflowers (Platycodon grandiflorum) using Acetobacter pasteurianus A11-2 and analyzed bellflower vinegar (BV) samples using gas chromatography–mass spectrometry and quadrupole time-of-flight mass spectrometry over 15 days of fermentation to assess the quality. We also evaluated their antibacterial and immunoenhancing effects using RAW 264.7 macrophage cells. The major metabolites in BV are organic acids, with the main volatile compounds being ethyl acetate, isoamyl acetate, 1-pentanol, hydroxypropanoic acid, and malonic acid. When we fermented BV from unpeeled roots for 10 days with a starter culture, we observed significant antibacterial and immunoenhancing effects in macrophages. Therefore, we could determine the metabolite and functional differences in vinegar obtained from bellflower roots and proposed that bellflower roots with peel are an effective substrate for developing vinegar and healthy food products.

A novel low pH fermentation process for the production of acetate and propylene glycol from carbohydrate wastes

A novel low pH fermentation process was studied for the conversion of lactose using Lactobacillus plantarum and Lactobacillus buchneri under anoxic conditions in single co-culture, and two-stage sequential fermentations. This is aimed at producing acetate and propylene glycol (PG) as environmentally benign substitutes for currently used road and aircraft deicing chemicals. The results indicate that in the case of two-stage fermentation with immobilized L. buchneri in the second stage, lactose degradation rate increased markedly producing acetate and PG concentrations of 12.1 and 10.7 g L^-1 at pH 3.8. In the case of coculture fermentation, the acetate and PG concentrations were 8.2 and 6.8 g L^-1, respectively. Fermentation of lactose and whey powder was conducted at pH 4.25 using a high cell density culture of L. buchneri. The acetate and PG yields were similar for both substrates at ∼0.3 g/g and ∼0.33 g/g respectively. With a starting lactose concentration of 60 g/L, acetate and PG concentrations of 18 g/L and 21 g/L respectively were obtained. The low pH conversion of wastes to value-added products under anoxic conditions provides substantial operating benefits over neutral pH fermentations that require strict anaerobic conditions for effective operation. Moreover, the low product pH at around 4.0 will provide substantial savings in downstream processing costs due to the much higher extraction efficiency of weak- and moderate- base resins for acetic acid compared to acetate ion.

Improvement of the Flavor and Quality of Watermelon Vinegar by High Ethanol Fermentation using Ethanol-Tolerant Acetic Acid Bacteria

Acetic acid fermentation is an essential step in the production of high-quality fruit vinegar and typically involves the use of acetic acid bacteria (AAB). The present study showed that the high cell mass and acetic acid yields of ethanol-tolerant AAB under high ethanol conditions were related to the high activities and stability of both pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase and PQQ-dependent aldehyde dehydrogenase. Additionally, in acetic acid fermentation with watermelon wine (8 % ethanol), the main organic acids (acetic, tartaric and malic acids) produced by ethanol-tolerant Acetobacter pasteurianus AAB4 were higher than those by conventional A. pasteurianus AS1.41 (1.42-fold, 3.53-fold and 2.12-fold, respectively). Also, the main esters (ethyl acetate and phenylethyl acetate) produced by AAB4 were higher than those by AS1.41 (1.69-fold and 1.48-fold, respectively). In addition, the total sweet and umami free amino acids produced by AAB4 increased significantly. According to sensory analysis, the flavor, taste and overall acceptance score of watermelon vinegar produced by AAB4 were significantly higher than those by AS1.41. Therefore, high ethanol fermentation with ethanol-tolerant AAB improved the flavor and quality of watermelon vinegar, indicating that this technology can be applied to fruit vinegar production.

Effect of inoculation on strawberry fermentation and acetification processes using native strains of yeast and acetic acid bacteria

The aim of this work was to analyze the microbiota involved in the traditional vinegar elaboration of strawberry fruit during a spontaneous and inoculated process. In the spontaneous processes, low biodiversity was detected in both alcoholic fermentation (AF) and acetification. Nevertheless, a strain of Saccharomyces cerevisiae and of Acetobacter malorum were selected and tested as starter cultures in the inoculation study. The inoculated processes with these strains were compared with another spontaneous process, yielding a significant reduction in time for AF with a total imposition of the S. cerevisiae strain. The resulting strawberry wine was acetified in different containers (glass and wood) yielding an initial imposition of the A. malorum inoculated strain, although displacement by Gluconacetobacter species was observed in the wood barrels.