Nutrient Utilization during Bioreactor Culture, and Maturation of Somatic Embryo Cultures of Picea mariana and Picea Glauca-engelmannii

Embryogenic cell cultures of Picea mariana (black spruce) and the species complex Picea glauca-engelmannii (interior spruce) were maintained either as suspensions in liquid medium in 250 or 500-ml-capacity shake-flasks, 7-liter-capacity airlift or mechanically stirred bioreactors, or on agar-solidified medium. Cultures from each of the maintenance conditions were subsequently transferred to agar-solidified LP medium containing$40 \mu M (\pm)-abscisic$acid for maturation into cotyledonary stage embryos. For both species, the highest maturation frequency resulted from cultures grown in the airlift bioreactor. With black spruce cells grown in the airlift bioreactor containing LP medium with 60 mM sucrose, a maximum of$7.1 g \cdot liter^{-1}$dry weight and$2892 embryos \cdot ml^{-1}$were obtained after 15 days. For interior spruce cells, a maximum dry weight of$5.9 g \cdot liter^{-1}$and$2698 embryos \cdot ml^{-1}$were obtained after 21 to 30 days. During culture over 2 wk, ammonia was almost completely utilized by both species, whereas nitrate was depleted to 40% of the initial concentration. Sucrose was rapidly hydrolyzed to glucose and fructose by both species. Black spruce cultures preferentially metabolized glucose, whereas interior spruce preferentially metabolized fructose. Improved growth of interior spruce cells in mechanically stirred bioreactors occurred when cultured in LP medium with 60 mM fructose as the sole carbon source.