Lactic Acid Bacteria Fertiliser Boosts Rapeseed Growth and Selenium Uptake, Study Finds

Selenium deficiency is a quiet but widespread public health problem. Across large parts of the world, soils contain too little of this essential trace element, and the crops grown in them carry that shortfall straight to the dinner table. Because humans obtain almost all of their selenium from food, agronomists have long searched for ways to raise the selenium content of staple and vegetable crops without resorting to expensive or environmentally risky interventions. A new study published in Environmental Geochemistry and Health offers a promising candidate: a fertiliser built around selenium-enriched lactic acid bacteria, which researchers report can simultaneously boost plant growth, improve the plant’s antioxidant defenses, reshape the rhizosphere microbiome, and rewire gene expression in leaves.

The research, conducted by a team at the College of Biological Engineering at Henan University of Technology in Zhengzhou, China, focused on rapeseed, a crop of global importance both as a source of edible oil and as a vegetable. Rapeseed is also known for its ability to accumulate selenium, which makes it an attractive target for biofortification, the practice of increasing the density of vitamins and minerals in crops through agronomic, breeding, or biotechnological means. The team set out to answer a question that has lingered in the biofortification literature: while selenium-enriched bacterial fertilisers have shown potential in earlier work, their combined effects on plant physiology, antioxidant systems, soil bacterial communities, and gene-level regulation had never been systematically examined in a single experiment.

To do this, the researchers designed a pot experiment with three treatments. The first was a control group receiving no selenium or bacterial amendment. The second received a selenium fertiliser without any bacterial inoculation, applied as sodium selenite, the inorganic form of the element most commonly used in fertilisation trials. The third received the star of the study: a selenium-enriched bacterial fertiliser designated LB-2, in which lactic acid bacteria had been used to convert and store selenium before the material was applied to the soil. This design allowed the team to isolate precisely what the living bacterial component added beyond the selenium itself, a distinction that matters enormously for anyone hoping to commercialise such a product.

The results on plant growth were unambiguous. Compared with plants that received selenium alone, those treated with the selenium-enriched bacterial fertiliser grew significantly taller and accumulated significantly more fresh weight. Their soluble sugar content was also higher, a marker often associated with improved metabolic status and stress resilience in plants. In other words, the bacteria were not merely a delivery vehicle for selenium; they actively contributed to the plant’s overall vigor. This aligns with a growing body of literature showing that lactic acid bacteria can act as plant growth-promoting microorganisms, in some cases solubilising phosphate and improving nutrient availability in calcareous soils, as the same group has previously reported for other crops including tomato and rapeseed seedlings.

Perhaps the most striking single number in the study is the organic selenium conversion rate. In the bacterial fertiliser treatment, 79.26 percent of the selenium taken up by the plants was converted into organic forms. This figure matters because the chemical form of selenium determines both its nutritional value and its safety. Inorganic selenite, the form applied to the soil, can be toxic at relatively low concentrations and is not always well utilised by the human body. Organic selenium compounds, by contrast, such as selenomethionine incorporated into proteins, are the forms in which selenium is most effectively absorbed and used in human metabolism, and they carry a lower risk of toxicity. A fertiliser that pushes the plant’s own biochemistry toward organic selenium is therefore doing double duty: it enriches the crop and makes that enrichment safer and more bioavailable.

The team also examined how the treatments affected the plant’s antioxidant machinery. When plants take up exogenous sodium selenite, they experience a degree of oxidative stress, an imbalance between reactive oxygen species and the systems that neutralise them. Plants respond with a suite of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), which together dismantle the most damaging reactive molecules. In the rapeseed leaves, the bacterial fertiliser treatment produced antioxidant enzyme activity that was more effective at reducing this oxidative stress than the activity measured in plants given selenium alone. The implication is that the bacteria helped the plants cope with the very selenium that was being delivered to them, smoothing the physiological transition from inorganic exposure to organic incorporation.

Below ground, the story was equally compelling. Using 16S rRNA gene sequencing, the standard molecular tool for cataloguing bacterial communities, the researchers analysed the rhizosphere soil, the narrow zone of soil immediately surrounding the roots where plant and microbe engage in a constant chemical conversation. The bacterial fertiliser treatment significantly enriched several beneficial taxa, including Sphingomonas, Paraflavitalea, and Neorhizobium. These are not random names. Sphingomonas species are widely documented as plant growth promoters and agents of environmental remediation, capable of degrading pollutants and modulating plant stress responses. Neorhizobium belongs to a lineage of bacteria famous for their associations with legumes and their capacity to improve soil fertility. Their enrichment in the rhizosphere suggests that the lactic acid bacterial fertiliser does not simply add one species but reorganises the entire below-ground ecosystem in a direction favorable to the plant.

The final layer of the investigation reached into the plant’s own genome. Transcriptome sequencing of the rapeseed leaves, which measures which genes are active and to what degree, revealed significant alterations in the expression of key genes involved in secondary metabolic pathways. Among the genes whose expression changed were P5CS2, which encodes an enzyme central to proline biosynthesis, a pathway intimately linked to stress tolerance and osmotic adjustment; NCED4, a gene involved in the biosynthesis of abscisic acid, the hormone that orchestrates plant responses to drought and other stresses; and ZEP, which participates in the zeaxanthin epoxidase step of the carotenoid and abscisic acid pathways. Together, these changes indicate that the bacterial fertiliser does not just feed the plant or its microbes; it sends signals, direct or indirect, that reprogram the plant’s metabolic priorities toward stress management and secondary metabolism.

Taken together, the study sketches a coherent mechanistic picture. The selenium-enriched lactic acid bacterial fertiliser operates on four fronts at once. It enhances the conversion of inorganic selenium into organic, bioavailable forms within the plant. It strengthens the plant’s antioxidant defenses, allowing growth to continue despite the oxidative challenge posed by selenite. It enriches the rhizosphere with bacterial taxa known to improve soil fertility and support plant growth, potentially creating a self-reinforcing loop in which healthier roots exude compounds that further favor beneficial microbes. And it modulates leaf gene expression in ways that reshape secondary metabolism, the branch of plant biochemistry responsible for many of the compounds that determine nutritional and defensive quality. No single one of these effects would be remarkable on its own; their integration in a single fertiliser treatment is what makes the finding notable.

The practical implications extend beyond rapeseed. Roughly half a billion people worldwide are estimated to consume insufficient selenium, and regions with selenium-poor soils, including parts of China, Europe, and Africa, face persistent challenges in delivering adequate amounts of the element through ordinary diets. Agronomic biofortification with inorganic selenium salts has been tried for decades, but it faces hurdles of cost, leaching, and the narrow window between beneficial and toxic doses. A bacterial fertiliser that improves conversion to organic forms could widen that safety margin while adding the co-benefits of growth promotion and soil health. The authors suggest that their LB-2 fertiliser offers a viable strategy for increasing selenium levels in food crops, and the study’s multi-omics approach, combining plant physiology, enzyme assays, microbiome sequencing, and transcriptomics, provides a template for how such claims should be evaluated. As with any pot experiment, the next test will be whether these effects hold up in the field, across seasons, and in the variable soils where selenium deficiency actually bites. But the direction of travel is clear: the microbes in the soil, and now the microbes in the fertiliser, are becoming partners in the effort to grow more nutritious food.

Subject of Research: Use of selenium-enriched lactic acid bacterial fertiliser to enhance rapeseed growth and selenium biofortification

Article Title: Mechanism of lactic acid bacterial fertiliser on enhancing growth and selenium absorption of rapeseed revealed by transcriptome analysis and rhizosphere bacterial diversity

Article References: Li, F., Zhang, Y., Sun, J., Wu, G., Guo, J., Li, H., Wang, X., & Qu, J. (2026). Mechanism of lactic acid bacterial fertiliser on enhancing growth and selenium absorption of rapeseed revealed by transcriptome analysis and rhizosphere bacterial diversity. Environmental Geochemistry and Health, 48(16), Article 632. https://doi.org/10.1007/s10653-026-03529-6

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03529-6

Keywords: selenium, biofortification, lactic acid bacteria, rapeseed, rhizosphere microbiome, transcriptomics, plant growth promotion, antioxidant enzymes, organic selenium, soil bacteria, sodium selenite, Environmental Geochemistry and Health