Effect of post-harvest conditions on antioxidant enzyme activity in Dunaliella tertiolecta biomass

Abstract

Microalgae biomass is considered a sustainable feedstock to produce high-value compounds including enzymatic and non-enzymatic antioxidants, which are widely used for food, pharmaceuticals, textile, leather , and in the chemical industries. Suitable post-harvest storage conditions to minimise deterioration of enzyme activity is therefore crucial. In this study, the effect of storage temperature over time on antioxidant enzyme activity (catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) in four D. tertiolecta samples (whole wet cells, freeze-dried whole cells, crude extract and freeze-dried crude extract) were evaluated. Antioxidant enzyme activities in freshly harvested whole cells or in the crude extract stored at -20 °C were retained only for up to one month but when stored at -80 °C, both CAT and SOD activities remained unchanged for four months. Moreover, in the freeze dried whole cell samples, CAT and SOD activities were retained for 8 months at -20 °C, however, when a crude extract was prepared and freeze dried, enzyme activities decreased. Therefore, careful control of storage temperature could prevent unfavourable changes to antioxidant activity in harvested cells thereby increasing shelf-life and the value of this type of biomass. This study recommends a suitable post-harvest storage temperature for preservation of Dunaliella biomass for both short-term and long-term stability of antioxidant enzyme activities. Our results strongly indicate that fresh whole cell extracts should be used in antioxidant enzyme assays , but if storage is necessary, whole fresh cells should be freeze dried and stored at -80 °C. Crude extracts prepared should be used in antioxidant enzyme assays within 24 h of preparation. • Evaluating the effect of storage temperature and time on antioxidant enzyme activity in Dunaliella biomass . • Assessing temperature-induced oxidative stress during storage of Dunaliella cells. • Post-harvest storage recommendations to minimise deterioration of antioxidant enzyme activity in Dunaliella biomass.