Simultaneous production of acetic and gluconic acids by a thermotolerant Acetobacter strain during acetous fermentation in a bioreactor

Abstract

The activity of bacterial strains significantly influences the quality and the taste of vinegar. Previous studies of acetic acid bacteria have primarily focused on the ability of bacterial strains to produce high amounts of acetic acid. However, few studies have examined the production of gluconic acid during acetous fermentation at high temperatures. The production of vinegar at high temperatures by two strains of acetic acid bacteria isolated from apple and cactus fruits, namely AF01 and CV01, respectively, was evaluated in this study. The simultaneous production of gluconic and acetic acids was also examined in this study. Biochemical and molecular identification based on a 16s rDNA sequence analysis confirmed that these strains can be classified as Acetobacter pasteurianus. To assess the ability of the isolated strains to grow and produce acetic acid and gluconic acid at high temperatures, a semi-continuous fermentation was performed in a 20-L bioreactor. The two strains abundantly grew at a high temperature (41 C). At the end of the fermentation, the AF01 and CV01 strains yielded acetic acid concentrations of 7.64% (w/v) and 10.08% (w/v), respectively. Interestingly, CV01 was able to simultaneously produce acetic and gluconic acids during acetic fermentation, whereas AF01 mainly produced acetic acid. In addition, CV01 was less sensitive to ethanol depletion during semi-continuous fermentation. Finally, the enzymatic study showed that the two strains exhibited high ADH and ALDH enzyme activity at 38 C compared with the mesophilic reference strain LMG 1632, which was significantly susceptible to thermal inactivation.

Effect of synthetic microbial community on nutraceutical and sensory qualities of kombucha

“…Additionally, acetic acid can produce an astringent and acidic off‐flavour, and its generation is undesirable in fermented beverages (Bartowsky & Henschke, 2008). It was reported that acid‐producing profiles in various Acetobacter strains are quite different (Mounir et al , 2016). A. pasteurianus strain used in this study mostly produces a high proportion of gluconic acid and a small amount of acetic acid.…”

Aroma profile of pilot plant-scale produced fruit vinegar using a thermotolerant Acetobacter pasteurianus strain isolated from Moroccan cactus

“…This strain was selected for its thermotolerant properties and for its high acetic acid production capacity. 19 On the other hand, this study aimed also to perform a comparative chemical and sensory analysis between the produced vinegar (using selected strains in pilot plant-scale bioreactor) and common ones manufactured in a traditional manner available in local market. For this purpose, Headspace solid-phase micro-extraction (HS-SPME) technique was used for analyzing aromatic compounds in vinegars.…”

Biotechnologically relevant features of gluconic acid production by acetic acid bacteria

“…11,[17][18][19][20][21][22] Similarly to fungi -albeit with different enzymes -, these bacteria oxidize glucose virtually stoichiometrically to GA via glucono-δ-lactone. 21 The oxidation reaction occurs in the bacterial periplasm and is effected by a membrane-bound pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) located in the outer side of the cytoplasmic membrane; glucose and the resulting GA may undergo other biotransformation reactions depending on the particular operating conditions.…”