New developments in oxidative fermentation

Abstract

Oxidative fermentations have been well established for a long time, especially in vinegar and in L-sorbose production. Recently, information on the enzyme systems involved in these oxidative fermentations has accumulated and new developments are possible based on these findings. We have recently isolated several thermotolerant acetic acid bacteria, which also seem to be useful for new developments in oxidative fermentation. Two different types of membrane-bound enzymes, quinoproteins and flavoproteins, are involved in oxidative fermentation, and sometimes work with the same substrate but produce different oxidation products. Recently, there have been new developments in two different oxidative fermentations, D-gluconate and D-sorbitol oxidations. Flavoproteins, D-gluconate dehydrogenase, and D-sorbitol dehydrogenase were isolated almost 2 decades ago, while the enzyme involved in the same oxidation reaction for D-gluconate and D-sorbitol has been recently isolated and shown to be a quinoprotein. Thus, these flavoproteins and a quinoprotein have been re-assessed for the oxidation reaction. Flavoprotein D-gluconate dehydrogenase and D-sorbitol dehydrogenase were shown to produce 2-keto- D-gluconate and D-fructose, respectively, whereas the quinoprotein was shown to produce 5-keto- D-gluconate and L-sorbose from D-gluconate and D-sorbitol, respectively. In addition to the quinoproteins described above, a new quinoprotein for quinate oxidation has been recently isolated from Gluconobacter strains. The quinate dehydrogenase is also a membrane-bound quinoprotein that produces 3-dehydroquinate. This enzyme can be useful for the production of shikimate, which is a convenient salvage synthesis system for many antibiotics, herbicides, and aromatic amino acids synthesis. In order to reduce energy costs of oxidative fermentation in industry, several thermotolerant acetic acid bacteria that can grow up to 40 degrees C have been isolated. Of such isolated strains, some thermotolerant Acetobacter species were found to be useful for vinegar fermentation at a high temperature such 38-40 degrees C, where mesophilic strains showed no growth. They oxidized higher concentrations of ethanol up to 9% without any appreciable lag time, while alcohol oxidation with mesophilic strains was delayed or became almost impossible under such conditions. Several useful Gluconobacter species of thermotolerant acetic acid bacteria are also found, especially L-erythrulose-producing strains and cyclic alcohol-oxidizing strains. Gluconobacter frateurii CHM 43 is able to rapidly oxidize meso-erythritol at 37 degrees C leading to the accumulation of L-erythrulose, which may replace dihydroxyacetone in cosmetics. G. frateuriiCHM 9 is able to oxidize cyclic alcohols to their corresponding cyclic ketones or aliphatic ketones, which are known to be useful for preparing many different physiologically active compounds such as oxidized steroids or oxidized bicyclic ketones. The enzymes involved in these meso-erythritol and cyclic alcohol oxidations have been pu...

Acetic Acid Bacteria: Physiology and Carbon Sources Oxidation

“…Sugar Alcohols Oxidation AAB can oxidize several sugar alcohols like glycerol to DHA, D-mannitol to D-fructose, D-sorbitol to L-sorbose, Darabitol to xylulose, D and meso-erythritol to L-erythrulose [1,7]. Particularly in winemaking, AAB can use glycerol as carbon source which is converted into DHA by the glycerol dehydrogenase; an enzyme bound with the cellular membrane inducing a high accumulation of DHA in the media.…”

“…Through processes called ''oxidative fermentations'', AAB perform specific oxidation reactions and channel the released electrons to molecular oxygen. Due to these ability they are known since a long time especially for their role in vinegar production [7].…”

Complete genome sequence of the acetic acid bacterium Gluconobacter oxydans

“…1). The latter protein catalyzes D-sorbitol oxidation to D-fructose and can be used for the biotechnological production of this sweetener 5 . It has been shown that membrane-bound dehydrogenases transfer electrons to ubiquinone, which functions as electron donor for the quinol oxidases 27 .…”

“…They also can be used industrially to produce D-gluconic acid, and ketogluconic acids from D-glucose and dihydroxyacetone from glycerol 5 . Strains of this genus also produce aliphatic, aromatic carboxylic and thiocarboxylic acids that find applications as flavoring ingredients 6 .…”

Screening of Acetic Acid Producing Microorganisms from Decomposed Fruits for Vinegar Production

“…The interest of vinegar production using acetic acid bacteria may also economically profitable [11]. For oxidative fermentation, huge development in isolation, identification and characterization of this group of bacteria were found [12] [13]. In this study, we intended to isolate acetic acid bacteria from the natural sources (decomposed fruits) of Bangladesh to assess their potentiality for vinegar production.…”