Harvesting of freshwater microalgae with microbial bioflocculant: a pilot-scale study

Abstract

BackgroundNowadays, bioflocculation is considered as a potential technology that could be able to alleviate microalgae dewatering cost regarded as the cornerstone hindrance of their full-scale application. However, most bioflocculation studies reported are laboratory scales. This study examined a pilot-scale and in situ flocculation of freshwater microalgae Desmodesmus brasiliensis by microbial bioflocculant. Biochemical composition of microalgal biomass was analyzed to evaluate the applicability of bioflocculation for microalgae-based biofuel production.ResultsThe flocculation efficiency >98 % was achieved at both pilot-scale and in situ treatment. Bioflocculation is simple, effective, economic, and environmentally friendly. Even though total proteins recovered from biomass harvested by centrifugation and that harvested by bioflocculation were significantly different, there was no significant difference in total carbohydrates and total lipids recovered from either biomass harvested by centrifugation or biomass harvested by bioflocculation.ConclusionThe results herein presented, doubtlessly demonstrated that the γ-PGA bioflocculant produced by Bacillus licheniformis CGMCC 2876 is applicable for commercial-scale microalgae harvesting. In addition, bioflocculation process cost could greatly be reduced by in situ operation as no investment cost is needed for a separate flocculation tank and mixing device. Furthermore, bioflocculation method developed is a worthy microalgae harvesting method for algal-based biofuel production.Graphical abstractThe addition of bioflocculant to microalgae cultures followed by mixing elicits, the formation of heavy flocs which settle out by gravity sedimentation in a relatively short settling time.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0458-5) contains supplementary material, which is available to authorized users.

A Review on the Use of Microalgae for Sustainable Aquaculture

“…Owing to the serious threats caused by metal accumulation in food chain, metal-ions based flocculation can not be considered as a safe and eco-friendly technology. Recently, some studies reported the coagulation effects of natural polymers, such as protein and polysaccharide, secreted by microorganisms [78,79]. Generally, by natural-polymer based flocculation, the harvesting efficiency of microalgae could reach 90% [78,80].…”

“…Recently, some studies reported the coagulation effects of natural polymers, such as protein and polysaccharide, secreted by microorganisms [78,79]. Generally, by natural-polymer based flocculation, the harvesting efficiency of microalgae could reach 90% [78,80]. Therefore, it is suggested that in aquaculture, to harvest microalgae by flotation-flocculation, natural polymers can be used for safety purpose.…”

The effect of the algal microbiome on industrial production of microalgae

“…Wang et al isolated a novel bacterium HW001 from Permian groundwater and demonstrated that this strain is able to stimulate aggregation of both Nannochloropsis oceanica IMET1 and other potential biofuel-producing green microalgae, diatoms and cyanobacteria (Wang et al, 2012a). In addition, two potent bioflocculants have been discovered from culture supernatant of Burkholderia cepacia (Manheim and Nelson, 2013) and Bacillus licheniformis CGMCC 2876 (Ndikubwimana et al, 2016). High flocculation efficiency of Desmodesmus brasiliensis (> 98 %) was achieved at pilot-scale treatment with poly-c-glutamic acid, a bioflocculant produced by Bacillus licheniformis CGMCC 2876 (Manheim and Nelson, 2013).…”

Algae-Derived Bioactive Compounds with Anti-Lung Cancer Potential

“…New low-cost harvesting technology is required to make the whole process sustainable since harvesting is considered as a major challenge as it is requiring almost 30% of the total cost of the pharmaceuticals production process. Different initiatives are recently developed but still they didn't meet the viability [109][110][111][112]. Furthermore, the extraction process that is efficient, safe for the molecules, economically feasible and environmentally friendly is far from being a reality.…”