STUDY ON BATCH CULTURES WITHOUT PH CONTROL AND DIFFERENT NUTRITIONAL CONDITIONS BY GLUCONACETOBACTER DIAZOTROPHICUS

MARTINI NANCY; MOLINARI M.L.; BOIARDI J.L.

MAR DEL PLATA

Congreso; VIII Congreso Argentino de Microbiología General. Sociedad Argentina de Microbiología General (SAMIGE).; 2012

SAMIGE (Sociedad Argentina de Microbiología General)

Gluconacetobacter diazotrophicus is an acid tolerant bacterium associated with sugarcane. This microorganism is an endophyte that can grow using N2 as the sole source of nitrogen. PGPP its rating stimulates the study of culture of this microorganism for the purpose of generating biomass and future development of a bio-inoculant. Also, G. diazotrophicus produced different biotechnological products such as gluconic acid and fructans. Extracellular production of gluconic acid is a biotechnology aspect of G. diazotrophicus because this organic acid is important in various industries. The main industrial use of gluconic acid is focused on the ability of this acids an acidifying agent and taste enhancer for food and medicine as excipients. In addition, gluconic acid is an excellent chelating used mainly in technical applications such as surface finishing of metal, textile fibers to inhibit precipitation and fouling. In adittion, the calcium gluconate and iron are used in the pharmaceutical industry in anemia. In other hand, fructans have received particular interest because of their excellent biological and functional properties for use as prebiotic compounds. They are used as components of functional food, are calories free and non cariogenic sweeteners, stimulate the growth of bifidobacteria, and have been claimed to contribute towards the prevention of colon cancer and to reduce cholesterol, phospholipid and triglyceride levels in serum. G. diazotrophicus secretes an extracellular levansucrase (LsdA) that hydrolyzes sucrose to produce free glucose and fructans of low (FOS) and high (levans) molecular weight. In this work we have studied the production of biomass, gluconic acid and levans in batch culture under diverses growth conditions and without pH control. Batch cultures of G. diazotrophicus PAL 5 were grown using LGIM medium at 30 °C. Different nutritional conditions have been tested; sucrose, glucose and glycerol as C source in different concentrations: 20 g/l (limited carbon source) and source 100 g/l (excess carbon source); BNF (N2 fixed), no-BNF (3 g/l inorganic nitrogen) and enrich with yeast extract and typtone (1.5 g/l either one). Under steady-sated conditions we have measured: biomass, exo-polysaccharides, glucose and gluconic acid production, and LsdA, GDH-PQQ, GaDH activity. In all of condition we observed a decreased of pH to 2 – 3 unit in the first 24 hs post-inocultaion. Also we detected gluconic acid production when glucose or sucrose were used as C source, but gluconic acid production were not detected when glycerol was used as C source. We detected a relationship between the C source used and the biomass production. In some of case, also we detected a relationship between the N source used and the biomass production. In this context, cultures with Y.E and tryptone were the best nitrogen condition for biomass production. We not detected levans production. This lack of levans production is because in the pH of culture the levans were hydrolized.