Gluconic acid production in synthetic media by using e. coli w pqq+ and e. coli w pqq+vgb+ recombinant strains

In this study, gluconic acid production properties from glucose based media by using two different E. coli W recombinant strains which are obtained by studies conducted in a TUBİTAK (117R003) Project were investigated. While the E. Coli W pqq+vgb- strain has only heterologous PQQ gen, E. coli W pqq+vgb+ strain has vitrocilla haemoglobin gen besides the PQQ gen. The results of the studies to determine important media constituents for gluconic acid production by using Placket-Burman Experimental design technique showed that the important components are Na2HPO4, yeast extract, CaCO3 besides the glucose for both strains. A second experimental design study was made by using Central Composite Design (CCD) method to optimize the amount of these media components. The optimum concentrations of media components for both strains were determined as 150 g/L of glucose, 1.5 g/L Na2HPO4, 7.5 g/L of yeast extract and 30 g/L of CaCO3. In the erlen studies, for the optimized media composition under the conditions of 30 C of temperature and 200 rpm of shaking speed, maximum gluconic acid concentrations for both strains were determined as about 150 g/L. Some bioreactor experiments were conducted under the conditions of 30℃ of temperature, 650 rpm of stirring rate, 3 L/min of air feeding for optimized media composition. The results of bioreactor study showed that the gluconic acid fermentation was completed in about 32 hours for both strains. Thus it can be said that the fermentation process in bioreactor is about 4.5 fold faster than the erlen studies. As a result, it can be concluded that the recombinant strains obtained from E. coli W have important advantages such as high efficiency and fast fermentation compered with classical microorganisms such as A. niger.