Continuous gluconic acid production by isolated yeast-like mould strains of Aureobasidium pullulans

Abstract

By extensive microbial screening, about 50 strains with the ability to secrete gluconic acid were isolated from wild flowers. The strains belong to the yeast-like mould Aureobasidium pullulans (de Bary) Arnaud. In shake flask experiments, gluconic acid concentrations between 23 and 140 g/l were produced within 2 days using a mineral medium. In batch experiments, various important fermentation parameters influencing gluconic acid production by A. pullulans isolate 70 (DSM 7085) were identified. Continuous production of gluconic acid with free-growing cells of the isolated yeast-like microorganisms was studied. About 260 g/l gluconic acid at total glucose conversion could be achieved using continuous stirred tank reactors in defined media with residence times (RT) of about 26 h. The highest space-time-yield of 19.3 g l(-1) x h(-1)) with a gluconic acid concentration of 207.5 g/l was achieved with a RT of 10.8 h. The possibility of gluconic acid production with biomass retention by immobilised cells on porous sinter glass is discussed. The new continuous gluconate fermentation process provides significant advantages over traditional discontinuous operation employing Aspergillus niger. The aim of this work was the development of a continuous fermentation process for the production of gluconic acid. Process control becomes easier, offering constant product quality and quantity.

Continuous gluconic acid production by Aureobasidium pullulans with and without biomass retention

“…Novel superior processes were developed and optimized for the continuous and discontinuous production of gluconic acid by isolated strains of Aureobasidium pullulans during an extensive process development program (Anastassiadis et al 1999;Anastassiadis et al 2003;Anastassiadis et al 2005). A defined fermentation medium was composed and optimized, which makes it easy to reproduce those data.…”

“…Optical density (OD 660 nm ), dry biomass (filter method) and the concentration of glucose and gluconic acid were determined as has described in previous works (Anastassiadis, 1993;Anastassiadis et al 1999;Anastassiadis et al 2003;Anastassiadis et al 2005). …”

“…70 (DSM 7085), which was isolated from wild flowers (Jülich, Germany) was used during the entire work (Anastassiadis et al 1999;Anastassiadis et al 2003;Anastassiadis et al 2005). Yeast malt extract agar plates (YME), inoculated with Aureobasidium pullulans, were incubated for 2-3 days and stored at 4ºC.…”

“…alkali metal salts, in especially sodium gluconate) have found extensively versatile uses in the chemical, pharmaceutical (e.g. iron and calcium deficiency), food, beverage, textile and other industries (Hustede et al 1989;Anastassiadis et al 2003;Znad et al 2004). Additionally, it can be exploited for cleaning purposes (e.g.…”

“…The immobilization of whole cells or glucose oxidase enzyme by various techniques has often been reported to be a useful approach to the production of gluconic acid or other microbial metabolites (Hartmeier and Döppner, 1983;Pronk et al 1989;Sakurai et al 1989;Gromada and Fiedurek, 1997;Nakao et al 1997;Kara and Bozdemir, 1998;Velizarov and Beschkov, 1998;Anastassiadis et al 1999;Sankpal et al 1999;Bang et al 1999;Ferraz et al 2000;Bao et al 2001;Blandino et al 2001;Klein et al 2002;Anastassiadis et al 2003;Godjevargova et al 2004;Anastassiadis et al 2005;Mukhopadhyay et al 2005). Fluidized bed reactors have been often used for several fermentation applications, in especially for anaerobic processes.…”