Barley malt is the main raw material of beer production, which is prepared from barley by steeping, germinating and kilning (Verma et al., 2022). F. graminearum infection has emerged as one of the major safety and quality issues in the malt industry (Liu et al., 2022; Del Ponte et al., 2012). In the infection process, F. graminearum can lead to the decrease of grain yield, and also produce DON to cause a threat to human's health (Kalagatur et al., 2018; C. Sun et al., 2016). It has been reported that an important source of DON in barley malt is the secretion of F. graminearum during the malting process (Jiang et al., 2023). Therefore, it is essential to develop an effective method to inhibit the growth of F. graminearum during the malting process.

The use of fungicides is the most common inhibition method of F. graminearum (Chala et al., 2003; Yin et al., 2009). Although fungicides are highly effective in killing F. graminearum, their high toxicity and environmental pollution have been under debate in recent years (Chen et al., 2022b; Li et al., 2023). Biological control method is considered an “environmentally friendly” strategy, and the basic principle is to inhibit or kill F. graminearum through the mutual inhibition of microorganisms (Liu et al., 2019; Wang et al., 2022). However, the intermediate process of biological control method is uncontrollable, and most are at the laboratory research stage (Wu et al., 2019; Wang et al., 2019a, Wang et al., 2019b). Therefore, there is an urgent requirement to develop novel methods to kill F. graminearum effectively during the malting process.

In recent years, photocatalyst technology has emerged as a new method to inhibit the growth of food pathogenic microorganisms (Fonseca et al., 2021). Compared with conventional sterilization methods, photocatalytic technology does not increase the tolerance of pathogenic microorganisms, and has the advantages of green, environmentally friendly and efficient. There are reports on the application of photocatalysts in killing Escherichia coli (Li et al., 2019), Salmonella typhimurium (Shi et al., 2022), Bacillus cereus (Kim et al., 2021), Aspergillus flavus (Sun et al., 2021), Staphylococcus aureus (Wang et al., 2019a, Wang et al., 2019b) and F. graminearum (Zhang et al., 2014). However, the application of photocatalysis in the food industry still faces some challenges. On the one hand, most of the photocatalytic materials used in the current reports contain metal elements, which may precipitate harmful metal ions during the photocatalytic process and lead to food safety hazards (Zhao et al., 2021a). On the other hand, the light source used in some photocatalytic reactions is ultraviolet light, which is expensive and can destroy the nutrients and flavor substances of grains (He et al., 2019).

g-C3N4 is considered as a new generation of metal-free photocatalytic material after the traditional metal photocatalytic materials such as TiO2, ZnO and WO3 (Wang et al., 2009; Zhao et al., 2021a, Zhao et al., 2021b). Compared with the traditional metal-based photocatalytic materials, g-C3N4 has the advantages of high safety, visible light response, easy production and abundant sources of raw materials (Caudillo-Flores et al., 2021). Our group has prepared g-C3N4 homojunction with typical advantages of g-C3N4 and better photocatalytic performance than g-C3N4 by elemental doping, morphology control and composite construction (Chen et al., 2021; Chen et al., 2022a). However, it is unclear whether g-C3N4 homojunction can inhibit the growth of F. graminearum during malting without affecting the brewing quality of barley malt.

In addition, current studies on photocatalytic technology mainly focused on the production process of reactive radicals in photocatalytic systems (Zhao et al., 2020), while the inhibition mechanism of microbial growth by reactive radicals was ignored. Our work aimed to study the inhibition mechanism of F. graminearum growth by g-C3N4 homojunction and its application in barley malting. (1) The growth inhibition mechanism of F. graminearum was studied by examining its micromorphology, cell membrane selective permeability, differential metabolites and affected metabolic pathways in the ideal system. (2) The application feasibility of photocatalysis technology in the malting process was preliminarily investigated by studying the ergosterol and DON content, physicochemical indexes of barley malt.