Glucose metabolism and gluconic acid production by Acetobacter diazotrophicus

Abstract

Acetobacter diazotrophicus, a recently isolated nitrogen-fixing acidotolerant acetic acid bacterium, grew well in simple mineral media and exhibited high rates of gluconic acid formation. Glucose oxidation by the organism was less sensitive to low pH values than glucose oxidation by Gluconobacter oxydans. Growth and glucose oxidation were not affected by high gluconic acid concentrations. These observations indicate that A.diazotrophicus is an interesting organism for the industrial production of gluconic acid. The organism exhibited a high maintenance requirement (ms = 1.0 mmol glucose h -1 (g dry weight) -1) during glucose-limited growth in chemostat cultures at pH 3.5. Enzyme activities in cell-free extracts suggested that glucose metabolism in A. diazotrophicus proceeds exclusively via the hexose monophosphate pathway: the enzymes of the Embden-Meyerhof and Entner-Doudoroff pathways could not be detected. Both the phosphorylative and direct oxidative pathways of glucose metabolism appeared to be operative. In addition to a pyridine nucleotide (strictly NAD)-dependent glucose dehydrogenase, A. diazotrophicus contained a dye-linked, probably pyrrolo-quinoline quinone (PQQ)-dependent, glucose dehydrogenase. The latter activity seemed to be primarily responsible for gluconic acid formation.

Acetic Acid Bacteria: Physiology and Carbon Sources Oxidation

“…Acetobacter species can use sugars through the hexose monophosphate pathway and also through the EmbdenMeyerhof-Parnas and Entner-Doudoroff pathways [51]. Sugars are further metabolised to CO 2 and H 2 O via the TCA pathway, which is not functional in Gluconobacter.…”

Review: Gram Negative Bacteria in Brewing

“…Under acidic conditions the alcohol dehydrogenase activity of Acetobacter is comparatively more stable to the activity in Gluconobacter which results in more acetic acid production by Acetobacter [33]. A variety of carbohydrate sources such as arabinose, fructose, galactose, mannitol, mannose, ribose, sorbitol and xylose are utilised by AAB through the hexose monophosphate pathway [34], Embden-Meyerhof-Parnas (EMP) and EntnerDoudoroff (ED) pathway [35].…”

Assessing the Zinc solubilization ability of Gluconacetobacter diazotrophicus in maize rhizosphere using labelled 65Zn compounds

“…The basic principle behind this approach is decreasing the pH to 5 or below and making zinc soluble and as a consequence the available zinc will get increased in the soil system [22]. A term called zinc solubilizing bacteria (ZSB) was coined for those bacteria that are capable of solubilizing the insoluble zinc compounds / minerals in agar plate as well as in soil [17,2] A preliminary idea to solve zinc nutrition using a bacterium was put forward and further the mechanism behind the solubilization was elucidated under in vitro conditions by G. diazotrophicus -a prolifi c gluconic acid producing bacterium [3,18]. So far G. diazotrophicus was widely recognized because of its nitrogen fi xing ability [20].…”

“…Carbon fl ux was fi xed as 100 and the duration of the irradiation was about 6 days. The labelled ZnCO 3 and ZnO were applied on 17 th day after sowing at the rate of 0.117 g and 0.18 g respectively as per the treatment schedule.…”