ABSTRACT
Photoautotrophic gametophyte cells of the brown macroalgae Laminaria japonica were cultivated in 500ml stirred tank photobioreactors under seven pulse feeding modes and one batch mode.It is the first time for the study of effects of the feeding time points and feeding quantity on macroalgal cell growth and nutrient consumption.Results showed that, with inoculum density of 50mg DCW/L, in modified APSW artificial seawater medium at 13℃, light intensity of 60μE/m2.s, light cycle of 16/8h L/D, aeration rate of 50ml/min, and agitation speed of 100r/min, feeding the culture with small nutrient quantity was beneficial for the synchronization between nitrate and phosphate absorption, and further for biomass production.Feeding when ambient nutrient was abundant or depleted was quite weak for large amount of biomass accumulation, which might be due to the slowing nutrient absorption, nutrient storage, or the divergence absorption between nitrate and phosphate.Feeding nutrient frequently with small quantity from mid-exponential growth of macroalgal cells, that is maintaining medium nutrient concentration between 1/3 and 1/2 of its initial concentration, was the most effective way for biomass production, with biomass increased by 12.270 times of for 51 days' cultivation.
ABSTRACT
Photoautotrophic gametophyte cells of the brown macroalgae Laminaria japonica were cultivated in 500ml stirred tank photobioreactors under seven pulse feeding modes and one batch mode.It is the first time for the study of effects of the feeding time points and feeding quantity on macroalgal cell growth and nutrient consumption.Results showed that, with inoculum density of 50mg DCW/L, in modified APSW artificial seawater medium at 13℃, light intensity of 60μE/m2.s, light cycle of 16/8h L/D, aeration rate of 50ml/min, and agitation speed of 100r/min, feeding the culture with small nutrient quantity was beneficial for the synchronization between nitrate and phosphate absorption, and further for biomass production.Feeding when ambient nutrient was abundant or depleted was quite weak for large amount of biomass accumulation, which might be due to the slowing nutrient absorption, nutrient storage, or the divergence absorption between nitrate and phosphate.Feeding nutrient frequently with small quantity from mid-exponential growth of macroalgal cells, that is maintaining medium nutrient concentration between 1/3 and 1/2 of its initial concentration, was the most effective way for biomass production, with biomass increased by 12.270 times of for 51 days' cultivation.
ABSTRACT
Laminaria japonica gametophytic cells were cultivated in a photobioreactor under continuous shear stress (0-1000 r/min) in 60 hours and the following static cultivation within 23.5 days. The content of chlorophyll a reached the maximum value of 2.36 mg/L at the end of continuous shear stress when the agitation speed was 90 r/min, while the chlorophyll a (chl a) concentration decreased quickly and nitrogen and phosphorus were released under high shear force (270-1000 r/min). The cell injury ratio at 1000r/min was as 18 times as that of the control. During the recovery course, gametophytic cells showed themselves distinct recovery capability at all agitation speeds. Furthermore, the content of chl a is a more exact index as biomass than dry cells weight (DCW). Besides cell injury ratio, the liberation of phosphorus demonstrates the cells injury.