Characterization of storage stability of microalgal biomass for its applications as protein feed ingredients in animal and aquafeeds

Abstract

Microalgae has recently attracted a significant interest as a sustainable source of nutrients for feed industry. Therefore, it is important to gain a comprehensive understanding on safety, physical and biochemical qualities, and storage stability of the microalgae products intended for use in feeds. This work is a time course evaluation of nutritional and safety parameters of microalgal biomass (Picochlorum sp.) produced under outdoor conditions. Initially, physical properties, proximate composition, aflatoxins, and pathogenic bacterial count of dried microalgal biomass (control = 0 days of storage) were evaluated. The bulk density and tapped density were 0.61 ± 0.005 and 0.86 ± 0.005 g m/L, respectively. 81% of particle size of microalgal biomass powder was below 212 µm size. Protein (~43% w/w), constituted the main component of the proximate composition, followed by carbohydrates (20%) and lipids (18%). Aflatoxins and pathogenic bacterial cell counts were within the regulatory limits, as per the US and EU regulatory guidelines for feed ingredients. Further, the microalgal biomass was stored under three storage conditions: cold storage 4 ± 3 °C (CS), warehouse storage 30 ± 5 °C (WH) and laboratory storage 23 ± 3 °C (LS) and periodically evaluated for stability of above-mentioned parameters. Crude protein concentration did not change over 12 months of storage. An increase (by 3.2%) in moisture content was observed under LS storage conditions with respect to control after 12 months. However, it did not alter the nutritional quality, aflatoxins, or microbial load. Moreover, the amino acids profile remained stable throughout the entire duration of storage. Vitamin D showed a significant decline after 3 months of storage. Results from this study conclude that microalgae can be stored at any of the three storage conditions tested, without compromising the proximate composition of the biomass for a period of 12 months.