Biomass and Flocculation Characteristics of Picochlorum Oklahomensis and Nannochloropsis Oculata

Abstract

In this study, two microalgae strains, Picochlorum oklahomensis (PO) and Nannochloropsis oculata (NO), were examined for their biomass properties and harvesting characteristics. Three flocculation methods, pH adjustment, biopolymer (chitosan) addition and electroflocculation, were investigated for effective harvesting of algal biomass. A generalized linear mixed model using a beta distribution for response was utilized to optimize the processing variables. The results obtained from characterization of microalgae indicated that PO and NO can be potential feedstock for biofuel production. Adjusting the pH of algae suspensions to 11–13 resulted in effective biomass flocculation efficiency, 90.5–97.0 % for PO and above 99 % for NO. The highest flocculation efficiency obtained from the flocculation by chitsoan addition was 98.4 % for PO, and 99.8 % for NO. The highest electroflocculation efficiency was 99.7 % for PO, and 99.4 % for NO. In conclusion, pH adjustment, chitosan addition and electroflocculation were effective methods to flocculate PO and NO cells under the conditions examined in this study. The scalability of these flocculation techniques for commercial algal biomass production needs to be further examined. The selection of the most suitable flocculation technique and the optimum treatment conditions would be based not only on the application of algal biomass, but also on a feasibility study.