Microalgal Reactors: A Review of Enclosed System Designs and Performances

Abstract

One major challenge to industrial microalgal culturing is to devise and develop technical apparata, cultivation procedures and algal strains susceptible of undergoing substantial increases in efficiency of use of solar energy and carbon dioxide. Despite several research efforts developed to date, there is no such thing as "the best reactor system"- defined, in an absolute fashion, as the one able to achieve maximum productivity with minimum operation costs, irrespective of the biological and chemical system at stake. In fact, choice of the most suitable system is situation-dependent, as both the species of alga available and the final purpose intended will play a role. The need of accurate control impairs use of open-system configurations, so current investigation has focused mostly on closed systems. In this review, several types of closed bioreactors described in the technical literature as able to support production of microalgae are comprehensively presented and duly discussed, using transport phenomenon and process engineering methodological approaches. The text is subdivided into subsections on: reactor design, which includes tubular reactors, flat plate reactors and fermenter-type reactors; and processing parameters, which include gaseous transfer, medium mixing and light requirements.

Photo-autotrophic Production of Poly(hydroxyalkanoates) in Cyanobacteria

“…This generally means the cyanobacteria are no longer able to repair the photosystem II (PSII), which further leads to a loss in the activity of the oxygen-evolving complex. 38,39,40 As the cells should not constantly remain in the dark, sufficient mixing is crucial. In a photobioreactor, this means a turbulent flow has to be maintained to allow the cells a continuous change between light and dark zone.…”

“…Although closed systems are more complex, they offer a better control of crucial parameters, and at the same time contamination becomes less likely. 40 The main challenges in any photobioreactor system are: light availability, CO 2 introduction, O 2 removal and sufficient mixing. Despite all the advantages, it has to be stated clearly that closed systems are much more expensive than open pond systems, provided that the ground area is cheaply available.…”

Cyanobacterial Farming for Environment Friendly Sustainable Agriculture Practices: Innovations and Perspectives

“…The cost of these systems is increased significantly by application of transparent materials but the closed system helps in preventing contamination of grazers and competitors. Such systems are designed in a manner which provides a higher surface to volume ratio, and therefore, cell densities obtained are often higher than in open systems (Carvalho et al, 2006).…”

A method of batch-purifying microalgae with multiple antibiotics at extremely high concentrations

“…At present, photoautotrophic culture is widely adopted for most microalgae. Unfortunately this is heavily infl uenced by multiple environmental factors including light defi ciency; temperature fl uctuation; and microalgal, bacterial and protozoan contamination, all of which result in low and unstable productivity (Zhang et al, 1999;Lee, 2001;Carvalho et al, 2006;Chisti, 2007). Early studies have documented that many microalgal species are able to grow by metabolizing organic carbon (Chojnacka and Marquez-Rocha, 2004;Chen and Chen, 2006;Sloth et al, 2006;Bumbak et al, 2011;Perez-Garcia et al, 2011), making the heterotrophic culture of microalgae feasible.…”