Magnetic Immobilization and Growth of Nannochloropsis oceanica and Scenedasmus almeriensis

Microalgae are used in industrial and pharmaceutical applications. Their performance on biological applications may be improved by their immobilization. This study presents a way of cell immobilization using microalgae carrying magnetic properties. Nannochloropsis oceanica and Scenedasmus almeriensis cells were treated enzymatically (cellulase) and mechanically (glass beads), generating protoplasts as a means of incorporation of magnetic nanoparticles. Scanning electron microscopy images verified the successful cell wall destruction for both of the examined microalgae cells. Subsequently, protoplasts were transformed with magnetic nanoparticles by a continuous electroporation method and then cultured on a magnetic surface. Regeneration of transformed protoplasts was optimized using various organic carbon and amino acid supplements. Both protoplast preparation methods demonstrated similar efficiency. Casamino acids, as source of amino acids, were the most efficient compound for N. oceanica protoplasts regeneration in enzymatic and mechanical treatment, while for S. almeriensis protoplasts regeneration, fructose, as source of organic carbon, was the most effective. Protoplasts transformation efficiency values with magnetic nanoparticles after enzymatic or mechanical treatments for N. oceanica and S. almeriensis were 17.8% and 10.7%, and 18.6% and 15.7%, respectively. Finally, selected magnetic cells were immobilized and grown on a vertical magnetic surface exposed to light and without any supplement.

Comparative studies of protoplast development in jack pine (Pinus banksiana)

Protoplasts were isolated either from the cotyledons of 8- to 10-day-old seedlings, or from cell suspensions, initiated from seedlings of the same open-pollinated seedlot of jack pine (Pinus banksiana Lamb.). Protoplast yields were 2.0 – 7.0 × 105/g fresh wt. for cotyledon-derived, and 0.3–5 × 105/g fresh wt. for suspension-derived protoplasts. Cotyledon protoplasts (6.8%) divided after 5 to 8 days incubation in liquid Lainé medium C with 450 mM glucose as osmoticum. Small clusters of 6 to 10 cells, which were observed after approximately 2 weeks, formed microcalli upon further dilution of the culture medium. By 6 to 8 weeks, these microcalli could be transferred to solid medium using a nurse culture of jack pine cells. Protoplasts isolated from seven cell suspension lines differed in their responses to culture conditions. First divisions were only observed with two cell lines cultured in either Lainé medium C or one-half Litvay with 370 mM glucose, but this did not lead to callus development. Key words: jack pine, Pinus banksiana, cotyledons, protoplasts, regeneration, callus.