Bioflocculant Technology Implementation Using Navicula sp for Harvesting of Arthrospira Platensis Culture

Abstract

Bioflocculation, a microalgae harvesting method utilizing organisms like
bacteria and microalgae as flocculant agents, necessitates careful selection
and ratio determination of bioflocculant agents. This study seeks to ascertain
the optimal balance of bioflocculant, Navicula sp., for metabolite production
and harvesting efficiency in Arthrospira platensis culture. Spanning three oneweek cultivation stages, the research commences with A. platensis culture
under varying salinities (0, 15, 25, and 35 ppt) in the first stage, followed by
pH variations (9, 10, 11, and 12) in the second stage. The optimal salinity-pH
combination identified in the first two stages is applied in the third stage,
involving bioflocculant addition to culture and medium solutions at varying
ratios (0.25:1, 0.5:1, 0.75:1, and 1:1 v/v). Precipitation efficiency and
pigmentation were measured using spectrophotometry, while lipid content
was determined by the Bligh & Dyer extraction method. Carbohydrate content
was assessed using the Phenol-Sulphuric Acid assay, and protein content
was quantified using the Bradford protein assay. The findings indicate salinity,
pH, and bioflocculant influence A. platensis growth, metabolite production,
and harvesting efficiency. Optimal outcomes are achieved at 15 ppt salinity,
pH 9, and a 1:1 ratio of bioflocculant, yielding 1.18x10-3 g of dry biomass,
3.56x105 cells/mL of cell density, 2.9x100 g/L of carbohydrates, 3.63x100 g/L
of lipids, 9.97x10-3 mg/L of chlorophyll a+b, 8.71x10-1 mg/L of carotenoids,
and 3.04x10-1 g/L of protein. These results suggest that salinity addition, high
pH, and the addition of Navicula sp. as bioflocculant increase the harvesting
process efficiency of A. platensis culture.