Effects of renewal regime on consumption of nitrogen and phosphorus, biomass and polysaccharide production by Porphyridium cruentum in semicontinuous culture

摘要

In order to probe the effects of the renewal rate and the renewal period on the cell biomass, nutrients consumption and extracellular polysaccharide production, the Porphyridium cruentum was cultivated semicontinuously in the 30L flat plate photobioreactor. The results showed that the growth rate of microalgae followed a progressive rise with the increase of renewal rate and fall with the extension of renewal period in the culture. The maximum output rate of the cell biomass (85.78 mg/L/d and 231 mg/L/d) and polysaccharide output rate (26.27 mg/L/d and 26.81 mg/L/d) were achieved with the renewal rate of 30% and renewal period of 5d, respectively. The total recovery yield followed a parabolic distribution with the increase of the renewal rates and the renewal period, while the maximal recovery yield of biomass (79.72 g and 196.82 g) were achieved at the renewal rate of 40% and renewal period of 4d, respectively. Similarly, the highest recovery yields of polysaccharide (21.21 g and 23.23 g) were observed at the renewal rate of 30% and renewal period of 4 d, respectively. The extension of renewal period and decrease of renewal proportion resulted in the absence of nitrogen and phosphate in semicontinous system, consequently affecting the cell growth and polysaccharide production. The results indicated that different renewal regimes based on the different objectives should be applied for obtaining maximum production in semicontinuous cultures of microalgae. In this study, the optimum regime for maximal recovery yield of extracellular polysaccharide from Porphyridium cruentum was 29.4% of renewal rate and 4.1 d of renewal period. Under this condition, the total recovery yield of polysaccharide was 26.81 g, and the maximum of biomass was 191.08 g, which were 270% and 38.2% higher than that in batch culture.