title: 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.
authors.affiliation: Hassan II Institute of Agronomy and Veterinary Medicine (IAV), PO Box 6202, Rabat, Morocco; Walloon Centre of Industrial Biology, University of Liege, B40, B-4000 Sart-Tilman, Belgium. Electronic address: mounirmajid@gmail.com.
authors.forename: Majid
authors.initials: M
authors.lastname: Mounir
authors.affiliation: Department of Biology, Faculty of Science, University of Isfahan, Isfahan, Iran.
authors.forename: Rasoul
authors.initials: R
authors.lastname: Shafiei
authors.affiliation: Walloon Centre of Industrial Biology, University of Liege, B40, B-4000 Sart-Tilman, Belgium.
authors.forename: Raziyeh
authors.initials: R
authors.lastname: Zarmehrkhorshid
authors.affiliation: Hassan II Institute of Agronomy and Veterinary Medicine (IAV), PO Box 6202, Rabat, Morocco.
authors.forename: Allal
authors.initials: A
authors.lastname: Hamouda
authors.affiliation: Hassan II Institute of Agronomy and Veterinary Medicine (IAV), PO Box 6202, Rabat, Morocco.
authors.forename: Mustapha
authors.initials: M
authors.lastname: Ismaili Alaoui
authors.affiliation: Walloon Centre of Industrial Biology, University of Liege, B40, B-4000 Sart-Tilman, Belgium.
authors.forename: Philippe
authors.initials: P
authors.lastname: Thonart
mesh_terms: D019342:Acetic Acid / Q000378:metabolism*; D000091:Acetobacter / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D000426:Alcohol Dehydrogenase / Q000378:metabolism; D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D019149:Bioreactors; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D005638:Fruit / Q000382:microbiology; D005942:Gluconates / Q000378:metabolism*; D006358:Hot Temperature
chemical_list: D005942:Gluconates; D000431:Ethanol; D000426:Alcohol Dehydrogenase; D000444:Aldehyde Dehydrogenase; D019342:Acetic Acid; C030691:gluconic acid
keywords: Acetic acid; Acetobacter; Bioreactor; Enzyme activity; Gluconic acid; Thermoresistant