Effect of culture medium composition on the growth and biopolyesters production by the marine bacterium Saccharophagus degradans

The production of biomass and biopolyesters (polyhydroxyalkanoates) by the marine bacterium Saccharophagus degradans from: glucose, starch, glucosamine, and xylose were studied. The effect of yeast extract, trace elements, vitamins, and initial concentration of each carbon source on biomass production was evaluated. The addition of yeast extract, together with trace elements, increased the biomass production by 5-fold, obtaining the maximum values when using an initial substrate concentration of 20 g/L for: starch, 8.61; glucosamine, 7.06; and xylose, 4.47 (g dry cell weight/ L). From glucose at 40 g/L the maximum biomass production was 9.07 g/L. Next, the biopolymer production under nutrient-limiting conditions (by N, P, S and Mg) was investigated, as well as the ability of S. degradans to produce copolymers from precursors. The biopolyester produced in all cases was poly(3-hydroxybutyrate) (PHB). Different accumulation percentages (g PHB/100 g biomass) were achieved depending on the carbon source used: glucose, 27.72; starch, 18.11; glucosamine 3.33; there was not biopolymer accumulated from xylose. Finally, the PHB produced from each carbohydrate was characterized, presenting molecular weights between 53 and 58 KDa, and fusion temperatures between 164 and 174°C.