María Jesús Moreno Domínguez

Cadmium increases the activity levels of glutamate dehydrogenase and cysteine synthase in Chlamydomonas reinhardtii

Abstract The presence of 300 μM Cd2+ in culture medium was found to be toxic to Chlamydomonas reinhardtii, reducing growth and productivity by about 48%. Approximately 30% of the total cadmium in the medium was accumulated by the alga resulting in 0.88% of the algal dried biomass. Elemental analysis indicated a cadmium-dependent decrease in the C (about 3.2%) and N content (about 7.1%) within C. reinhardtii, while the S content increased by approximately 7.5%. In parallel, Cd2+ produced a significant activation of the aminating glutamate dehydrogenase (EC 1.4.1.2) activity and also NAD+- and NADP+-isocitrate dehydrogenase (EC 1.1.1.41 and 1.1.1.42, respectively) activities upon 24 h of the exposure to 150 μM of the metal. These data are consistent with the key role of the glutamate dehydrogenase/isocitrate dehydrogenase system to supply the glutamate required for the Cd2+-induction of phytochelatin synthesis in the alga. Moreover, the presence of cadmium in the culture medium enhances the sulfate uptake rate and the components of the cysteine synthase complex within the cells such as the serine acetyltransferase (EC 2.3.1.30) and O-acetyl-L-serine (thiol)lyase (EC 4.2.99.8) activities.

Microalgae: Fast-Growth Sustainable Green Factories

Microalgae are definitely on the way to become a sustainable, fast-growing natural green source for highly demanded market products. Research is currently looking at promising outstanding applications of microalgae among which are the production of biofuels from the fatty acids present in biomass, functional foods enriched with microalgae healthy bioactive molecules, and greenhouse gas mitigation (CO2 consuming) based on high cell density microalgae cultures technology. Besides, other traditional microalgae applications are currently increasing in competitiveness in a growing market demand for green biomass, in which microalgae are widely recognized as a healthy, sustainable, and biological renewable resource. Among these traditional applications, microalgae are being used to improve the nutritional quality in animal feed, particularly in aquaculture, therapeutic agent source, and antioxidant activity. In addition, microalgae also show to be functional in waste effluents treatment to remove N and P, thus preventing eutrophication, heavy metals, and others contaminants. This review intends to offer a comprehensive overview of basic aspects of microalgae physiology, massive production of biomass, and current fields of applications at industrial scale.