Study on batch cultures without pH control and different nutritional conditions by Gluconacetobacter diazotrophicus

MARTINI, N.; MOLINARI M.L; BOIARDI J.L

Mar del Plata, Buenos Aires.

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

Sociedad Argentina de Microbiología General (SAMIGE).

Gluconacetobacter diazotrophicus is an acid tolerant bacterium associated with sugarcane. G. diazotrophicus is an endophyte that can grown using N2 as source of nitrogen. G .diazotrophicus is a PGPP. It stimulates the study of culture of this microorganism for produce biomass and future development to a bio-inoculant. Also, G. diazotrophicus produced different biotechnological products such as gluconic acid and fructans. The industrial applications of gluconic acid are: as acidifying agent and taste enhancer for food and medicine as excipients; gluconic acid is an excellent chelating used in technical applications such as surface finishing of metal, textile fibers to inhibit precipitation and fouling. In addition, the calcium gluconate and iron are used in the pharmaceutical industry in anemia. In other hand, fructans have excellent biological and functional properties for use as prebiotic compounds and functional food. The fructans are is calories free and no 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 studied the production of biomass, gluconic acid and levans in batch culture under different growth conditions 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 (C-limited) and 100 g/l (C-excess); BNF (N2 fixed), No-BNF (3 g/l (NH4)2SO4) and enrich with yeast extract and typtone (1.5 g/l either one). At different time, we have measured: biomass, exo-polysaccharides, glucose and gluconic acid production, and LsdA, GDH-PQQ, GaDH activity. In all of condition we observed a pH decreased to 2 ? 3 unit in the first 24 hs post-inocultaion. Also we detected gluconic acid production in culture with glucose or sucrose as C-source, but gluconic acid production was not detected in culture with glycerol. 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 when glucose or glycerol was used as C-source.