Hiroshima University researchers have shown that liquid waste from Japanese pickle production can be transformed into a source of valuable omega-3 fatty acids, opening a new route for converting food-industry byproducts into nutritional ingredients. In a study published in LWT – Food Science and Technology, the team cultivated the marine microorganism Aurantiochytrium sp. strain L3W in seasoning liquids discarded during the manufacture of traditional pickles. The microorganism produced docosahexaenoic acid, or DHA, and eicosapentaenoic acid, or EPA—two polyunsaturated fatty acids widely associated with human health and commonly supplied through fish oil, supplements, fortified foods and animal feeds. The researchers also demonstrated that the pickle waste could be used more than once, without sterilization, although repeated reuse gradually reduced productivity as inhibitory lactic acid accumulated.
DHA and EPA are long-chain omega-3 fatty acids with important biological functions. DHA is a structural component of cell membranes, particularly in the brain and retina, while EPA contributes to signaling pathways involved in inflammation and cardiovascular physiology. Despite their importance, humans produce only limited quantities of these fatty acids, making dietary sources significant. Fish oil remains the dominant commercial source, but dependence on wild-caught fish creates environmental, economic and supply-chain concerns. Thraustochytrids, a group of marine, fungus-like microorganisms, have emerged as an alternative because many species can accumulate large quantities of lipids inside their cells. Unlike fish, these microorganisms can be cultivated in controlled systems and can manufacture omega-3 fatty acids directly from organic carbon sources.
The Hiroshima University study focused on strain L3W, a thraustochytrid isolated and characterized by a research group led by Satoshi Nakai in 2021. The organism belongs to the genus Aurantiochytrium, whose members are known for their ability to convert dissolved nutrients into intracellular oils rich in DHA and, in some cases, EPA. Rather than relying on refined sugars or expensive laboratory substrates, the researchers tested liquid seasoning waste generated by three varieties of tsukemono, the traditional Japanese pickles: Hiroshimana, sakura radish and umeboshi. These waste liquids contain dissolved organic carbon and nitrogen that can support microbial growth, but they also contain organic acids produced during fermentation and preservation. The team therefore investigated both the nutritional potential and the biological limitations of the waste.
The experiments revealed that the three pickle-derived liquids could support cultivation of strain L3W, although their performance differed. The most promising substrate was waste from Hiroshimana pickles, known as HN waste. When used without dilution or additional nutrients, HN waste supported production of approximately 60.6 milligrams of DHA and 2.5 milligrams of EPA per gram under the study’s production conditions. These values were lower than those obtained with the conventional ATCC 790 By+ culture medium used as a control, but the result was scientifically important because the waste stream functioned as a growth medium without requiring supplementation. Eliminating added nutrients could reduce the cost of microbial production while simultaneously lowering the volume of liquid waste sent for treatment or disposal.
The researchers’ most striking finding was that the HN waste medium did not need to be discarded after a single cultivation cycle. Once the first culture had been harvested, the spent liquid was used again to grow strain L3W and produce additional DHA and EPA. The microorganism was able to grow during the repeated cycles, confirming that usable nutrients remained in the liquid after the first fermentation. However, the fatty-acid content declined with reuse. After two reuses, the concentration of lactic acid reached approximately 2.7 grams per liter, and additional experiments confirmed that lactic acid inhibited strain L3W. This result identifies a specific chemical bottleneck in the recycling process: the waste is not exhausted simply because its nutrients disappear, but because fermentation-derived acid progressively creates conditions that restrict microbial growth and lipid biosynthesis.
Lactic acid can affect microorganisms in several ways. In an acidic medium, the undissociated form of the molecule can cross the cell membrane and then dissociate inside the cell, disrupting intracellular pH and forcing the organism to spend energy on maintaining chemical balance. Acid stress can also interfere with enzyme activity, nutrient transport and the metabolic pathways that direct carbon toward storage lipids. For Aurantiochytrium, this matters because DHA and EPA synthesis requires carbon and energy to be diverted into specialized fatty-acid pathways rather than basic cell maintenance. The study’s findings suggest that future process improvements could involve removing lactic acid, adjusting pH, diluting the waste or integrating an additional treatment step between cultivation cycles. Such measures might increase the number of possible reuses, although they would need to be evaluated against the cost and environmental benefits of the system.
The proposed approach could have a measurable effect at the level of an individual pickle factory. The researchers report that an average Hiroshimana pickle facility generates roughly 100 tons of liquid seasoning waste each year. Based on their experimental yields, they estimate that this volume could produce about 26 kilograms of DHA and 810 grams of EPA. These quantities are modest compared with the output of large industrial fermentation plants, but the concept is designed around a different advantage: converting a local waste stream into a higher-value product while reducing the need for new feedstocks. In regions where food factories, microbial production facilities and aquaculture operations can be connected geographically, the same liquid could move through a circular production chain rather than becoming a disposal burden.
The potential applications extend beyond dietary supplements. DHA- and EPA-rich microbial biomass could be incorporated into feed for farmed fish, where omega-3 enrichment is important for the nutritional quality of aquaculture products. The Hiroshima University team is also interested in whether strain L3W biomass could be fed to laying hens to produce eggs enriched with DHA and EPA. This strategy would use the microorganism as an intermediate biological factory: pickle waste would supply nutrients to the thraustochytrid, the resulting biomass would be consumed by poultry, and the fatty acids could then enter the human food supply through eggs. Similar concepts are already being explored with algae and other microorganisms, but the distinctive feature of this study is the repeated use of an untreated food-processing liquid and the direct identification of lactic acid as the factor limiting that recycling.
The work represents a proof of feasibility rather than a finished industrial process. Large-scale production will require careful control of contamination, seasonal variation in pickle composition, salt concentration, acidity and the presence of compounds that may change from one factory to another. Nonsterile cultivation can reduce energy and equipment requirements, but it also creates competition from native bacteria and fungi. Researchers will need to determine how consistently strain L3W can dominate under real manufacturing conditions and whether the harvested biomass meets safety standards for feed or food-related applications. Economic analyses will also be necessary to compare waste transport, pretreatment, cultivation, harvesting and purification with conventional sources of DHA and EPA. Nevertheless, the study establishes an important principle: liquid food waste can serve as a renewable carbon and nitrogen reservoir for omega-3 biosynthesis, and its repeated use can extend the value extracted from the same resource.
By linking Japanese food traditions with marine biotechnology, the researchers have turned a highly specific waste problem into a model for circular biomanufacturing. Their results show that carbon discarded during pickle production can be redirected into DHA and EPA, compounds that are otherwise obtained largely from fisheries or manufactured using refined industrial ingredients. The discovery that the waste can be reused, together with the identification of lactic acid as the main constraint, gives future engineers a clear target for improving the process. If those limitations can be overcome, microbial platforms based on Aurantiochytrium could help produce omega-3 fatty acids with less pressure on marine ecosystems while creating new value from food waste. The study’s broader message is that the next generation of sustainable nutrition may be grown not from pristine raw materials, but from the overlooked liquids left behind by everyday food production.
Subject of Research: Aurantiochytrium sp. strain L3W cultivated in liquid pickle seasoning waste for the production of DHA and EPA.
Article Title: Repeated use of liquid pickle seasoning waste for the cultivation of Aurantiochytrium sp. in sustainable production of polyunsaturated fatty acids
News Publication Date: 21-Jul-2026
Web References: https://doi.org/10.1016/j.lwt.2026.119753
References: Anh Thi Nhat Tran, Satoshi Nakai, Toshikazu Suenaga, Takehiko Gotoh, Akira Umehara, Wataru Nishijima, and Radita Putradhitama Novanda. “Repeated use of liquid pickle seasoning waste for the cultivation of Aurantiochytrium sp. in sustainable production of polyunsaturated fatty acids.” LWT – Food Science and Technology, published 21 July 2026. DOI: 10.1016/j.lwt.2026.119753.
Image Credits: Satoshi Nakai / Hiroshima University
Keywords: DHA, EPA, omega-3 fatty acids, Aurantiochytrium, thraustochytrids, pickle waste, food waste upcycling, microbial biotechnology, circular bioeconomy, sustainable nutrition, lactic acid inhibition, Hiroshima University
