Effect of pH culture and dosage of chitosan nanoemulsion on the effectiveness of bioflocculation in harvesting Chlorella sp. biomass

Abstract

Chlorella sp. is a microalga with a size of less than 30 μm that requires a dewatering process to separate its biomass from the culture media, for instance using the flocculation method. In this study, chitosan nanoemulsion was used as the bioflocculant. The aim of this study was to investigate the effectiveness of harvesting Chlorella sp. biomass using chitosan nanoemulsion with varied doses and predetermined pH levels. The pH and bioflocculant dose affected the amount of biomass recovered during the harvesting process. The results showed that treatment at pH 9 and a dose of 2 gL-1 bioflocculant achieved the highest harvesting efficiency of 98.7%. The characterization of bioflocculant was carried out in the form of proximate analyses on chitosan nanoemulsion which resulted in 95% ash and 90% water contents. The appearance tests showed characteristics of yellow in color, sour aroma, and gel-shaped texture. The physical tests were also performed resulting in a pH of chitosan nanoemulsion of 4.3, viscosity of 15.5 cps, and a density of 1.912 cm/g. This study indicated that chitosan nanoemulsion is considered efficient for use as an alternative bioflocculant for harvesting Chlorella biomass.