Neochloris oleoabundans Growth Evaluation Under Different Nitrogen:Phosphorus:Carbon Feeding Strategies.

Microalgae are photosynthetic microorganisms known for their variety of compounds that can be useful for food, feed, pharmaceuticals, and fuel industries. Microalgae production costs have been one of the major obstacles to large-scale commercial production. Therefore, several studies are still being performed aiming to increase biomass by developing novel photobioreactor design and microalgae cultivation techniques. This work's purpose is to increase Neochloris oleoabundans biomass. Different nutrient-feeding regimes were tested in N. oleoabundans cultivation in Erlenmeyer flasks and bench-scale tubular photobioreactor. In Erlenmeyer flasks, the best concentrations of nitrate and phosphate were 8.82 mM and 5.16 mM, respectively. In bench-scale tubular photobioreactor, NaNO3 proved to be the best nitrogen source, in comparison with (NH4)2SO4 and NH4NO3. Still in the photobioreator, the addition of nitrate by fed-batch process combined with automated system of CO2 feeding showed to be of utmost importance for insuring a high density of N. oleoabundans. The essential nutrients evaluated in this work play an important role on N. oleoabundans biomass accumulation, as well as the photobioreactor configuration and feeding regimes.

Potential of Microalgae Carotenoids for Industrial Application.

Microalgae cultivation, when compared to the growth of higher plants, presents many advantages such as faster growth, higher biomass productivity, and smaller land area requirement for cultivation. For this reason, microalgae are an alternative platform for carotenoid production when compared to the traditional sources. Currently, commercial microalgae production is not well developed but, fortunately, there are several studies aiming to make the large-scale production feasible by, for example, employing different cultivation systems. This review focuses on the main carotenoids from microalgae, comparing them to the traditional sources, as well as a critical analysis about different microalgae cultivation regimes that are currently available and applicable for carotenoid accumulation. Throughout this review paper, we present relevant information about the main commercial microalgae carotenoid producers; the comparison between carotenoid content from food, vegetables, fruits, and microalgae; and the great importance and impact of these molecule applications, such as in food (nutraceuticals and functional foods), cosmetics and pharmaceutical industries, feed (colorants and additives), and healthcare area. Lastly, the different operating systems applied to these photosynthetic cultivations are critically discussed, and conclusions and perspectives are made concerning the best operating system for acquiring high cell densities and, consequently, high carotenoid accumulation.

Selenocystamine improves protein accumulation in chloroplasts of eukaryotic green algae.

Eukaryotic green algae have become an increasingly popular platform for recombinant proteins production. In particular, Chlamydomonas reinhardtii, has garnered increased attention for having the necessary biochemical machinery to produce vaccines, human antibodies and next generation cancer targeting immunotoxins. While it has been shown that chloroplasts contain chaperones, peptidyl prolylisomerases and protein disulfide isomerases that facilitate these complex proteins folding and assembly, little has been done to determine which processes serve as rate-limiting steps for protein accumulation. In other expression systems, as Escherichia coli, Chinese hamster ovary cells, and insect cells, recombinant protein accumulation can be hampered by cell's inability to fold the target polypeptide into the native state, resulting in aggregation and degradation. To determine if chloroplasts' ability to oxidize proteins that require disulfide bonds into a stable conformation is a rate-limiting step of protein accumulation, three recombinant strains, each expressing a different recombinant protein, were analyzed. These recombinant proteins included fluorescent GFP, a reporter containing no disulfide bonds; Gaussia princeps luciferase, a luminescent reporter containing disulfide bonds; and an immunotoxin, an antibody-fusion protein containing disulfide bonds. Each strain was analyzed for its ability to accumulate proteins when supplemented with selenocystamine, a small molecule capable of catalyzing the formation of disulfide bonds. Selenocystamine supplementation led to an increase in luciferase and immunotoxin but not GFP accumulation. These results demonstrated that selenocystamine can increase the accumulation of proteins containing disulfide bonds and suggests that a rate-limiting step in chloroplast protein accumulation is the disulfide bonds formation in recombinant proteins native structure.