1.Modification of the membrane-bound glucose oxidation system in Gluconobacter oxydans significantly increases gluconate and 5-keto-D-gluconic acid accumulation.
Merfort M1, Herrmann U, Ha SW, Elfari M, Bringer-Meyer S, Görisch H, Sahm H. Biotechnol J. 2006 May;1(5):556-63.
Gluconobacter oxydans DSM 2343 (ATCC 621H)catalyzes the oxidation of glucose to gluconic acid and subsequently to 5-keto-D-gluconic acid (5-KGA), a precursor of the industrially important L-(+)-tartaric acid. To further increase 5-KGA production in G. oxydans, the mutant strain MF1 was used. In this strain the membrane-bound gluconate-2-dehydrogenase activity, responsible for formation of the undesired by-product 2-keto-D-gluconic acid, is disrupted. Therefore, high amounts of 5-KGA accumulate in the culture medium. G. oxydans MF1 was equipped with plasmids allowing the overexpression of the membrane-bound enzymes involved in 5-KGA formation. Overexpression was confirmed on the transcript and enzymatic level. Furthermore, the resulting strains overproducing the membrane-bound glucose dehydrogenase showed an increased gluconic acid formation, whereas the overproduction of gluconate-5-dehydrogenase resulted in an increase in 5-KGA of up to 230 mM.
2.Acetobacter musti sp. nov. isolated from Bobal grape must.
Ferrer S1, Mañes-Lázaro R2, Benavent-Gil Y3, Yépez A4, Pardo I5. Int J Syst Evol Microbiol. 2015 Dec 4. doi: 10.1099/ijsem.0.000818. [Epub ahead of print]
An acetic acid bacterium (Bo7T), obtained during a study of the microbial diversity of spontaneous fermentations of Bobal grape must, was subjected to a polyphasic taxonomic study. Phylogenetic analysis based on 16S rRNA gene sequences allocated Bo7T in the genus Acetobacter, and revealed Acetobacter aceti and Acetobacter oeni to be nearest neighbours (99.57 % sequence similarity between Bo7T and A. oeni CECT 5830T, and 98.76 % between Bo7T and A. aceti CECT 298T). The cells are Gram-negative motile rods, catalase positive, and oxidase-negative. The DNA G+C content of Bo7T was 58.0 mol%. DNA-DNA hybridizations demonstrated that Bo7T belongs to a single novel genospecies that can be differentiated from its phylogenetically nearest neighbours by the following phenotypic characteristics: no production of 5-keto-D-gluconic acid from D glucose, growth with glycerol but not with methanol or maltose as sole carbon sources, and growth on yeast extract with 30% D glucose.
3.Acetobacter lambici sp. nov., isolated from fermenting lambic beer.
Spitaels F1, Li L, Wieme A, Balzarini T, Cleenwerck I, Van Landschoot A, De Vuyst L, Vandamme P. Int J Syst Evol Microbiol. 2014 Apr;64(Pt 4):1083-9. doi: 10.1099/ijs.0.057315-0. Epub 2013 Dec 20.
An acetic acid bacterium, strain LMG 27439(T), was isolated from fermenting lambic beer. The cells were Gram-stain-negative, motile rods, catalase-positive and oxidase-negative. Analysis of the 16S rRNA gene sequence revealed the strain was closely related to Acetobacter okinawensis (99.7 % 16S rRNA gene sequence similarity with the type strain of this species), A. ghanensis (99.6 %), A. syzygii (99.6 %), A. fabarum (99.4 %) and A. lovaniensis (99.2 %). DNA-DNA hybridization with the type strains of these species revealed moderate DNA-DNA hybridization values (31-45 %). Strain LMG 27439(T) was unable to grow on glycerol or methanol as the sole carbon source, on yeast extract with 10 % ethanol or on glucose-yeast extract medium at 37 °C. It did not produce acid from l-arabinose, d-galactose or d-mannose, nor did it produce 2-keto-d-gluconic acid, 5-keto-d-gluconic acid or 2,5-diketo-d-gluconic acid from d-glucose. It did not grow on ammonium as the sole nitrogen source and ethanol as the sole carbon source.
4.Gluconobacter cerevisiae sp. nov., isolated from the brewery environment.
Spitaels F1, Wieme A, Balzarini T, Cleenwerck I, Van Landschoot A, De Vuyst L, Vandamme P. Int J Syst Evol Microbiol. 2014 Apr;64(Pt 4):1134-41. doi: 10.1099/ijs.0.059311-0. Epub 2013 Dec 24.
Three strains, LMG 27748(T), LMG 27749 and LMG 27882 with identical MALDI-TOF mass spectra were isolated from samples taken from the brewery environment. Analysis of the 16S rRNA gene sequence of strain LMG 27748(T) revealed that the taxon it represents was closely related to type strains of the species Gluconobacter albidus (100 % sequence similarity), Gluconobacter kondonii (99.9 %), Gluconobacter sphaericus (99.9 %) and Gluconobacter kanchanaburiensis (99.5 %). DNA-DNA hybridization experiments on the type strains of these species revealed moderate DNA relatedness values (39-65 %). The three strains used d-fructose, d-sorbitol, meso-erythritol, glycerol, l-sorbose, ethanol (weakly), sucrose and raffinose as a sole carbon source for growth (weak growth on the latter two carbon sources was obtained for strains LMG 27748(T) and LMG 27882). The strains were unable to grow on glucose-yeast extract medium at 37 °C. They produced acid from meso-erythritol and sucrose, but not from raffinose.