Aquaculture is one of the fastest-growing food sectors, heavily relying on fishmeal as the primary protein source in aquafeeds. While fishmeal is rich in essential amino acids and lipids, its production from wild-caught, small pelagic fish raises concerns over sustainability and marine ecosystem degradation. As a promising alternative, the marine microalga Nannochloropsis oceanica offers high protein and amino acid content without requiring arable land or freshwater. However, its large-scale cultivation remains costly and environmentally burdensome due to reliance on synthetic mineral media. This thesis investigates the use of green juices freshly collected and mechanically pressed from various agricultural residues as alternative cultivation media for N. oceanica.
These plant-based juices are rich in macro- and micronutrients and represent a circular approach to valorize agricultural side streams. After identifying flower juice as a promising medium that supports sustained microalgal growth once supplemented with iron, calcium, and magnesium, protein was extracted from the resulting biomass and quantified for its potential application in aquafeed. A protein extraction yield of around 30% was obtained at 70 °C without any prior biomass disruption, indicating that thermal extraction can be a suitable technique to recover protein from this microalga.
This study demonstrates the potential of green juice-based cultivation systems to reduce the ecological footprint and cost of microalgal protein production, supporting more sustainable aquaculture practices.
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