Protoplast isolation in the marine brown alga Dictyopteris prolifera (Dictyotales)

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.

Protoplast isolation from Dictyopteris pacifica and Scytosiphon lomentaria, using a simple commercial enzyme preparation

BACKGROUND

Protoplasts (i.e., naked plant cells) can be used for in vitro manipulations and genetic improvement in cultivars with economic value. During the last decade, protoplast research in economic brown algae has been scarce, and it is usually hampered by the use of non-commercial enzymes or crude extracts for isolating protoplasts. Dictyopteris pacifica is part of a brown algal genus well known by its wide chemical diversity and biological properties. Scytosiphon lomentaria is an edible brown seaweed with antioxidant, antitumor, and antiviral properties. So far, there are no protoplast isolation protocols using commercial enzymes for these two economic brown algae. In this study, we obtained protoplasts from cultured samples of D. pacifica and S. lomentaria using commercially available enzymes. Additionally, we investigated the effects of Driselase inclusion and Ca-chelation pre-treatment on protoplast yields in order to optimize the conditions for protoplast preparations.

RESULTS

Protoplasts were isolated from Dictyopteris pacifica and Scytosiphon lomentaria using the commercially available Cellulase Onozuka RS (1%) and Alginate lyase (4 U mL-1), and short incubation time (4 h). Driselase did not show significant effects on protoplast production in both species. Ca-chelation pre-treatment only increased the number of protoplasts in D. pacifica. Under optimal conditions, the protoplast yields from D. pacifica and S. lomentaria were 4.83 ± 2.08 and 74.64 ± 32.49 × 106 protoplasts g-1 fresh weight, respectively. The values obtained for S. lomentaria were 2-3 orders of magnitude higher than previously reported.

CONCLUSIONS

Our results show that high protoplast yields can be obtained from D. pacifica and S. lomentaria using a simple mixture of commercial enzymes (Cellulase RS and Alginate lyase) and short incubation time (4 h). This work also represents the first report of protoplast isolation in D. pacifica. The method proposed here can help to expand protoplast technology in more brown algal species.