How harvesting frequency influence the biomass and lipid productivities of Nannochloropsis sp.

Abstract

Nannochloropsis is an algal species with a worldwide biotechnological interest. To improve biomass and lipid productivities of this alga while grown in outdoor paddle-wheel driven raceway ponds, different harvesting frequencies were implemented. Four harvesting frequencies (10% harvested, five days (R10F5), 20% harvested, three days (R20F3), 30% harvested, two days (R30F2) and 40% harvested, one day (R40F1) a week) were tested to identify their potential effects on biomass and lipid productivity. The highest biomass productivity of 41.7 ± 1.9 mgL−1d−1 was achieved when Nannochloropsis was harvested five days a week (R10F5). In general, the biomass productivity of Nannochloropsis sp. was R10F5 > R20F3 > R30F2 > R40F1. However, the highest lipid content of 59.7 ± 1.8% was obtained with one day a week harvesting frequency (R40F1). The obtained lipid content was found to be up to 50.7% higher than other treatments (R40F1 > R10F5 = R20F3 = R30F2). Due to significantly higher biomass productivity and lipid content, R10F5 and R40F1, respectively showed higher lipid productivity than other treatments (R10F5 = R40F1 ≥ R20F3 = R30F2). Based on the results, it can be concluded that harvesting frequency influences the biomass productivity and lipid content of Nannochloropsis and proper management of harvesting frequency would help to achieve optimum targeted product (biomass and/or lipid). If the aim is to generate biomass, high frequency of harvest is preferred; however, sacrificing the biomass productivity by lowering the frequency can significantly enhance the lipid content. In contrast, if the ultimate aim is mass production of both biomass and lipid, frequent harvesting is the solution.