Arachis hypogaea L, also known as peanut, belongs to the Fabaceae Lindl family. In china, the production of peanut has been 1799 tons (Zhu et al., 2021a). Fresh in-shell peanuts generally refer to the peanuts that are eaten directly after harvest or cooked, which retain the delicious taste and nutritional ingredients of fresh peanuts to a great extent (Wu et al., 2022). Freshly harvested in-shell peanuts are not only mixed with impurities such as soil, but also prone to water loss, deterioration and sprouting in a short period due to high moisture content, which makes it difficult to store fresh in-shell peanuts and restricts the development of fresh in-shell peanut industry (Smaoui et al., 2022). In addition, fresh in-shell peanuts are easily contaminated by soil-borne fungi such as Fusarium spp., Aspergillus spp. and Penicillium spp. (Yao et al., 2021; Lavrinenko et al., 2022). Fresh in-shell peanuts infected with soil-borne fungi may carry mycotoxins such as aflatoxin and deoxynivalenol, which could cause acute or chronic poisoning of humans and animals, posing a great threat to the health of humans and animals (Norlia et al., 2018). With the increasing attention to food safety and health issues and the increasing demand for friendly environment, it is of great significance to develop green, safe and efficient bio-fungicides for preventing and controlling mold infection in fresh peanuts.

As a green, safe and efficient bio-antifungal agent, the role of lactic acid bacteria (LAB) in preventing and controlling mold and mycotoxin contamination in agricultural products has been confirmed (Liu et al., 2024; Chen et al., 2023). The fermentation supernatant of Lactobacillus plantarum C10 was applied to muskmelon fruit and it was found that the supernatant could reduce the red rot of sweet melon fruit by enhancing the activity of phenylalanine ammonialyase, peroxidase and polyphenol oxidase and promoting the accumulation of phenols and flavonoids (Lv et al., 2018). A mixture of peptides extracted from Lactobacillus plantarum TE10 was applied to maize and it was found that the mixture could reduce the development of A. flavus spores by 4 times, which could be used as a biological control agent to control the growth of A. flavus on maize (Muhialdin et al., 2020). Lactobacillus amylovorus FST 2.11 and Lactobacillus amylovorus DSM20552 could reduce barley disease caused by Fusarium spp., and reduce deoxynivalenol content in barley spikelets (Byrne et al., 2022). Lactobacillus plantarum O2 fermentation supernatant treatment could enhance the tolerance of pepper under stress, slow down the damage caused by Phytophthora capsici and induce pepper resistance to Phytophthora capsica (Huang et al., 2023b). However, the research on the application of LAB in the storage of fresh in-shell peanuts is still scarce.

Fresh peanuts are easy to go bad due to various reasons during postharvest storage process, leading to serious economic losses (Wu et al., 2022). LAB strains have the potential to be bio-preservatives in peanut storage process, but the mechanism of LAB preventing and controlling mold contamination of fresh peanuts remains unclear. Recently, high-throughput omics approaches have been applied to understand the mechanism of peanuts to biotic and abiotic stresses, and in particular, integrated omics approaches are essential for elucidating the temporal and spatial changes that occur in peanut facing different stresses (Huang et al., 2023a). Transcriptomic-proteomic analysis revealed that many metabolic pathways in peanut were activated by improving key gene expressions and the contents of key enzymes that play critical roles in preventing fungi infection (Wang et al., 2024). Muti-omics were applied to probe the biological roles of key genes underlying peanut oil content and quality in peanuts which aimed to enhance peanut oil content and quality, and specific fatty acids components according to either human health needs or industrial requirements (Li et al., 2024a). Metabolomics-proteomics approaches were used to investigate the effect of oxygen levels in the storage environment on peanut protein oxidation and explore the mechanism (Li et al., 2024b).

In this research, the anti-mildew and fresh-keeping effect of LAB cell-free supernatant (CFS) on fresh in-shell peanuts during storage process was investigated by the experiments of total number of molds, diversity of fungal population, mildew rate, color change, firmness change, transcriptomic and metabolomic analysis, etc. This research aimed at providing a theoretical basis for LAB as anti-mildew agent for fresh in-shell peanut storage.