Biochemistry and biotechnological applications of Gluconobacter strains

Abstract

The genus Gluconobacter belongs to the group of acetic acid bacteria, which are characterized by their ability to incompletely oxidize a wide range of carbohydrates and alcohols. The corresponding products (aldehydes, ketones and organic acids) are excreted almost completely into the medium. In most cases, the reactions are catalyzed by dehydrogenases connected to the respiratory chain. Since the reactive centers of the enzymes are oriented towards the periplasmic space, transport of substrates and products into, and out of, the cell is not necessary. Thus, rapid accumulation of incompletely oxidized products in the medium is facilitated. These organisms are able to grow in highly concentrated sugar solutions and at low pH-values. High oxidation rates correlate with low biomass production, which makes Gluconobacter strains interesting organisms for industrial applications. Modern fermentation processes, such as the production of L-sorbose (vitamin C synthesis) and 6-amino- L-sorbose (synthesis of the antidiabetic drug miglitol) are carried out with members of this genus. Other important products are dihydroxyacetone, gluconate and ketogluconates. The bacteria belonging to the genus Gluconobacter exhibit extraordinary uniqueness not only in their biochemistry but also in their growth behavior and response to extreme culture conditions. This uniqueness makes them ideal organisms for microbial process development.

Nectar bacteria, but not yeast, weaken a plant–pollinator mutualism

“…Further, Gluconobacter is a member of the acetic acid bacteria, many of which frequently occur in nectar (e.g. Acinetobacter, Asaia) [17,18, electronic supplementary material, table S1] and cause similar chemical changes in solutions analogous to nectar [43,46]. In addition, microbial species richness is generally low within individual flowers, which often contain only one or a few species [23,26,47], perhaps due to strong competition and priority effects [22].…”

“…In addition, some birds are known to avoid highly acidic solutions [41,42], although little work has been done on hummingbirds specifically. Thus, the precipitous pH reduction by Gluconobacter-a species that has been used in vinegar production since prehistoric times [43]-may also have been responsible for the bacterial effects on pollination. Although striking, the level of Gluconobacterinduced reduction in pH (figure 3b) is within the range Hummingbirds respond more strongly to compounds within nectar than those emitted as volatiles [44] and may be unable to detect the presence of microbes in flowers without tasting nectar [45].…”

Characteristics and Kinetics of the Aldonic Acids Production using Whole-cell catalysis of Gluconobacter oxydans

“…1). The dehydrogenases components that are tightly bound to the bacterial membrane and linked to the cytochrome systems have been shown to control these oxidative reactions under the driving force of oxygen supply (Deppenmeier et al 2002;Gupta et al 2001). In the process of individual catalysis, the highest accumulation of AraA, XylA, GalA, GlcA, and ManA was about 25 g/L, 30 g/L, 29 g/L, 21 g/L, and 17 g/L, respectively.…”

“…In G. oxydans, there are various dehydrogenases, such as quinoprotein glucose dehydrogenase, quinoprotein gluconate-5-dehydrogenase which catalyzes the oxidation of D-gluconate and various alcohols, and quinohemoprotein alcohol dehydrogenase. G. oxydans also has a cytosolic-oxidizing enzyme system made up of NAD(P)-dependent dehydrogenases, which make only a minor contribution to overall oxidation (Gupta et al 2001;Deppenmeier et al 2002;Hölscher et al 2009). Furthermore, G. oxydans exhibits an extremely high tolerance towards lignocellulosic inhibitors, which is crucial for the development of a commercial fermentation (Buchert et al 1988;Buchert and Niemelä 1991).…”

Antifungal and Antipatulin Activity of Gluconobacter Oxydans Isolated from Apple Surface

“…Its species can grow in highly concentrated sugar solutions and at low pH values. Their growth behaviour and response to extreme culture conditions are remarkably unique (12).…”