Assessing different methods to preserve biochemical fractions in microalgal biomass for commercial applications

Abstract

Different methods exist for preserving microalgal biomass, but their relative effectiveness in maintaining the integrity of key biochemical constituents over an extended period of time remains unclear. This study compared the performance of different methods (refrigeration, freezing, freeze-drying, spray-drying, and oven-drying) for preserving different biochemical fractions (carbohydrates, lipids, proteins, chlorophyll a and carotenoids) of two commercially important microalgal species, Scenedesmus (Tetradesmus) obliquus and Chlorella vulgaris, over 43 days. Results show compound-specific and species-specific differences in degradation. In this study, carbohydrates in S. obliquus were best preserved by freezing, lipids by spray-drying, and proteins by freeze-drying. In contrast, carbohydrates and lipids in C. vulgaris were best preserved by oven-drying, and proteins by spray-drying. A decision chart based on different percent loss values aid operators to select the optimal preservation method, especially in cases where microalgal biomass is to be used to extract multiple chemical fractions. Beyond biochemical integrity, industrial-scale operations must also consider factors such as capital investment, energy consumption, labor and material costs, processing time and material loss. For example, oven-drying is inexpensive but has a long processing time, whereas spray-drying, while requiring higher capital and skill investment, has a fast throughput that may be more preferable in a competitive commercial space. This article provides practical recommendations for selecting appropriate preservation methods for algal biomass in both commercial and laboratory contexts, based on which a decision chart was formulated to aid operators in choosing the most appropriate preservation method.