Search

The green microalga Haematococcus pluvialis accumulates astaxanthin, a potent antioxidant pigment, as a defense mechanism against environmental stresses. In this study, we investigated the technical feasibility of a stress-based method for inducing astaxanthin biosynthesis in H. pluvialis using electric stimulation in a two-chamber bioelectrochemical system. When a cathodic (reduction) current of 3 mA (voltage: 2 V) was applied to H. pluvialis cells for two days, considerable lysis and breakage of algal cells were observed, possibly owing to the formation of excess reactive oxygen species at the cathode. Conversely, in the absence of cell breakage, the application of anodic (oxidation) current effectively stimulated astaxanthin biosynthesis at a voltage range of 2–6 V, whereas the same could not be induced in the untreated control. At an optimal voltage of 4 V (anodic current: 30 mA), the astaxanthin content in the cells electro-treated for 2 h was 36.9% higher than that in untreated cells. Our findings suggest that electric treatment can be used to improve astaxanthin production in H. pluvialis culture if bioelectrochemical parameters, such as electric strength and duration, are regulated properly. [ABSTRACT FROM AUTHOR]

Microalgae cells gained much attention as resources for food, drug, and biofuels. For last few decades, researchers have made efforts to increase the productivity in utilizing microalgae through genetic improvement by introducing plasmids or genes. However, the barriers of the cell wall and membrane hindered the efficient intracellular delivery and required the development of more effective strategy. Herein, we introduce the ultrasound-mediated transfer as a noninvasive and non-viral strategy and demonstrate its effectiveness in delivering fluorescent dyes and DNA into Chlamydomonas reinhardtii and Cholera vulgaris at high-frequency low-intensity (HFLI) (600 kHz-15 W) and low-frequency high-intensity (LFHI) (40 kHz-161 W) conditions. The HFLI ultrasound showed superior intracellular delivery of calcein, quantum dots, and cyano fluorescent protein (CFP) compared to the LFHI. The efficiency of the transient CFP expression by the HFLI was nearly two times greater than that of the conventional electroporation. PCR results also confirmed successful transfection of hygromycin phosphotransferase ( hpt ). The HFLI-induced observed enhancement in transfection presumably attributes to the mechanical resonance under stable cavitation oscillation, enhancing cell membrane permeability. To the best of our knowledge, this is the first report to show the HFLI ultrasound as an effective and viable route for intracellular delivery into microalgal cells. [ABSTRACT FROM AUTHOR]