Intermediate renewal rates enhance the productivity of the cyanobacterium Synechococcus sp. in semicontinuous cultures

The cyanobacterium Synechococcus sp. isolated from a hypersaline pond in Venezuela was cultured semicontinuously, at rates of daily renewal of the culture volume of 20, 30, 40 and 50 %, in order to establish the optimal renewal rate for pigment, protein, carbohydrate and exopolysaccharide (EPS) production. Maximal steady-state cell density, protein, chlorophyll a, carotenoids and carbohydrate production, of 265.6 x106 cell ml–1, 1.62 pg cell–1, 34.62 fg cell–1, 13.03 fg cell–1 and 222.84 μg ml–1 respectively, were achieved with a renewal rate of 20 %. On the other hand, maximal EPS production, 173.13 μg ml–1, was obtained at the 50 % daily renewal rate. Highest cell productivity, 84.49 x109 cell l-1 d–1, was found with a daily renewal rate of 50 %. Protein, chlorophyll a and dry weight productivity, 93.51, 2.48 and 134 mg l–1 d–1 were achieved with a renewal rate of 40 % per day. Carbohydrate and EPS productivities of 95.56 and 86.56 mg l–1 d–1, were higher with 50 %. This strain shows a high potential for biomass daily production enriched with EPS, chlorophyll and protein which is a function of the renewal rate in semicontinuous cultures.