A Mini Review on Microalgae Biomass Production: Recent Progress in Cultivation Systems

Single-celled photosynthetic microscopic algae (microalgae) have numerous significances for human wellbeing. From medicine to fuel industry these tiny organisms have tremendous potentials and in future they would be game changer to mitigate global warming and environmental pollutions. The current production cost is a matter of consideration during its applications. Scientists all over the world are trying to reduce the production costs as well as to develop new or improve the existing culturing methodologies and techniques. Open pond and closed pond (PBRs) culturing system are two most prominent ways to culture microalgae. Open pond culturing techniques for microalgae have several advantages over closed pond system such as low operational costs and easy to make. However, the main drawback of this system is contamination by other microorganisms, which is possible to control in closed pond system. Among the many types of PBRs systems, the advanced tubular PBRs presently considered as more useful than open pond culture system. To meet the minimum production costs, more research is needed on both the culturing systems.

Assessment of biomass potentials of microalgal communities in open pond raceways using mass cultivation

Metagenome studies have provided us with insights into the complex interactions of microorganisms with their environments and hosts. Few studies have focused on microalgae-associated metagenomes, and no study has addressed aquatic microalgae and their bacterial communities in open pond raceways (OPRs). This study explored the possibility of using microalgal biomasses from OPRs for biodiesel and biofertilizer production. The fatty acid profiles of the biomasses and the physical and chemical properties of derived fuels were evaluated. In addition, the phenotype-based environmental adaptation ability of soybean plants was assessed. The growth rate, biomass, and lipid productivity of microalgae were also examined during mass cultivation from April to November 2017. Metagenomics analysis using MiSeq identified ∼127 eukaryotic phylotypes following mass cultivation with (OPR 1) or without (OPR 3) a semitransparent film. Of these, ∼80 phylotypes were found in both OPRs, while 23 and 24 phylotypes were identified in OPRs 1 and 3, respectively. The phylotypes belonged to various genera, such as Desmodesmus, Pseudopediastrum, Tetradesmus, and Chlorella, of which, the dominant microalgal species was Desmodesmus sp. On average, OPRs 1 and 3 produced ∼8.6 and 9.9 g m−2 d−1 (0.307 and 0.309 DW L−1) of total biomass, respectively, of which 14.0 and 13.3 wt% respectively, was lipid content. Fatty acid profiling revealed that total saturated fatty acids (mainly C16:0) of biodiesel obtained from the microalgal biomasses in OPRs 1 and 3 were 34.93% and 32.85%, respectively; total monounsaturated fatty acids (C16:1 and C18:1) were 32.40% and 31.64%, respectively; and polyunsaturated fatty acids (including C18:3) were 32.68% and 35.50%, respectively. Fuel properties determined by empirical equations were within the limits of biodiesel standards ASTM D6751 and EN 14214. Culture solutions with or without microalgal biomasses enhanced the environmental adaptation ability of soybean plants, increasing their seed production. Therefore, microalgal biomass produced through mass cultivation is excellent feedstock for producing high-quality biodiesel and biofertilizer.