Reusing liquid pickle waste to produce omega-3 fatty acids
Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are omega-3 fatty acids known to have beneficial effects and are popular as functional foods and dietary supplements. They are polyunsaturated fatty acids (PUFAs); the primary source of these PUFAs for humans is fish oil.
A recent study by researchers at Hiroshima University reveals the potential of reusing liquid pickle waste to produce omega-3 fatty acids, specifically docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These polyunsaturated fatty acids, known for their health benefits, are primarily found in fish oil, but are also being explored as a sustainable byproduct of food processing waste.
The research team focused on three types of liquid pickle seasoning waste: Hiroshimana (HN), sakura radish (SR), and umeboshi (UB). Each of these pickles, known as tsukemono in Japanese cuisine, is rich in dissolved organic carbon and nitrogen, which serve as nutrient sources for the microorganism Aurantiochytrium sp. strain L3W. However, they also contain lactic acid, which inhibits both growth and PUFA production.
The researchers found that using Hiroshimana pickle waste directly, without sterilization or additional additives, was suitable for culturing strain L3W and producing DHA and EPA under nonsterile conditions. The undiluted HN medium yielded the highest amounts of the two fatty acids at 60.6 mg/g DHA and 2.5 mg/g EPA. Remarkably, the spent waste medium could be reused for another round of production, albeit with lower yields and increased lactic acid concentration.
This study is the first to demonstrate the feasibility of reusing food processing liquid waste for culturing a thraustochytrid to produce DHA and EPA. It also identifies lactic acid as an inhibitor that limits the number of possible reuses. With approximately 100 tons of liquid HN waste generated annually by a Hiroshima pickle factory, this method could potentially yield 26 kg (57 pounds) of DHA and 810 g (1.8 pounds) of EPA.
The findings suggest that recycling carbon from typical food waste into useful and functional omega-3 fatty acids is not only possible but also sustainable. The researchers propose exploring the use of strain L3W biomass in hen diets to enrich eggs, as well as in aquaculture to enhance live feed for fish hatcheries. This innovative approach could lead to the creation of a new brand of enriched eggs and contribute to the development of a more sustainable food industry.
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