Currently, as research on hydrogel beads intensifies, the application scope of chitosan-based hydrogel beads is increasingly expanding. Owing to their unique three-dimensional network structure, chitosan-based hydrogel beads are frequently utilized for encapsulating bioactive substances and adsorbing impurities. The primary material used in the preparation of chitosan-based hydrogel beads is chitosan, which is uniquely a natural polysaccharide possessing a positive charge. Derived from a diverse array of sources, chitosan is non-toxic, exhibits excellent biocompatibility, and possesses certain antibacterial properties. Because of these remarkable attributes, it has found widespread application in tissue engineering, the formulation of drug carriers, and the adsorption of heavy metals and dyes in wastewater. The preparation method for chitosan-based hydrogel beads largely mirrors that of other hydrogel beads. According to existing research, numerous methods exist for crafting hydrogel beads with diverse properties. This paper reviews the preparation methods of chitosan-based hydrogel beads, encompassing both physical and chemical crosslinking techniques. The physical crosslinking method leverages electrostatic interactions between materials to form hydrogel beads, whereas the chemical crosslinking method involves the use of chemical crosslinking agents to facilitate the formation of hydrogel beads through material-based chemical reactions. Given that chitosan carries a positive charge and other polysaccharide materials possess a negative charge, the combination of these materials can yield hydrogel beads with a dense structure, effectively encapsulating bioactive substances. This dense internal structure offers superior protection for the encapsulated bioactive substances. Chitosan-based hydrogel beads typically feature large pore sizes, providing numerous adsorption sites, which makes them well suited for wastewater treatment. Additionally, this paper examines the recent applications of chitosan-based hydrogel beads in food preservation, medicine, and environmental protection. Starting with the materials and methods for preparing chitosan-based hydrogel beads, this paper delves into their applications in food preservation, biomedicine, and environmental protection, offering insights for future developments and applications of chitosan-based hydrogel beads and fostering further innovation and advancement in this field.

The ability of the fungus to regulate metabolism on various nitrogen sources makes it survive and metabolize in different environments. The biomass and the β-glucan yield of Aureobasidium pullulans are closely associated with the nitrogen source. This study found the only GATA nitrogen source activation regulating factor Area in HIT-LCY³. In order to testify the Area function, we amplified its conserved domain to build a silencing vector and used the RNAi to obtain the Area silent strain, and then explored its effect on the phenotype of A. pullulans and the yield of β-glucan. We found that the biomass and β-glucan yield of the silent strain decreased significantly after culturing with different nitrogen sources, in particular when using sodium nitrate and glutamate as the source. However, the β-glucan yield increased significantly after overexpression of Area, reaching 5.2 g/L when glutamine was the nitrogen source. In addition, the strain morphology changed as well under different nitrogen sources. At last, we investigated the antioxidant activity in vitro of β-glucan and found that it has a significant clearance effect on OH·, DPPH·, and ABTS·, being best with ABTS. Therefore, this study believed that the Area gene has a certain regulation function on the synthesis of β-glucan with antioxidant activity.

Food packaging serves a pivotal role in daily life, facilitating the efficient transportation of food and extending its shelf life. Petroleum-derived plastic packaging is extensively employed; however, its non-biodegradable nature poses significant environmental pollution and ecological degradation. Natural polymers (e.g., proteins such as gelatin and corn gluten protein; polysaccharides including pectin, chitosan, starch, cellulose, and alginate) and synthetic polymers (e.g., polyvinyl alcohol, polylactic acid, and polyhydroxyalkanoates) can be utilized to fabricate food packaging films, thereby achieving green and eco-friendly objectives. Nevertheless, the inferior mechanical strength and inadequate antibacterial activity of biopolymer-based packaging have restricted their practical applications. In recent years, nanomaterials (e.g., nanoparticles, nanotubes, nanofibers, and nanosheets) have been employed to enhance the performance of food packaging, emerging as a research hotspot. Notably, nanoparticles possess unique properties, including a high specific surface area, excellent dispersibility, and multifunctionality, which enables them to be easily incorporated into film matrices. Owing to their unique chemical structures, nanoparticles form strong interactions with film matrices, leading to a denser spatial structure. This not only markedly enhances the mechanical strength of the films, but also simultaneously improves their antibacterial and antioxidant capabilities. This review classifies and summarizes common nanomaterials based on their chemical compositions, providing a theoretical foundation and technical reference for the future development and application of nanomaterials in the field of bio-based active food packaging.

Polysaccharides derived from diverse sources exhibit distinct rheological and gel properties, exerting a profound impact on their applicability in the food industry. In this study, we collected five Gracilaria chouae samples from distinct geographical regions, namely Rizhao (RZ), Lianyungang (LYG), Ningde (ND), Beihai (BH), and a wild source from Beihai (BHW). We conducted analyses on the chemical composition, viscosity, and rheological properties, as well as gel properties, to investigate the influence of chemical composition on variations in gel properties. The results revealed that the total sugar, sulfate content, and monosaccharide composition of G. chouae polysaccharides exhibit similarity; however, their anhydrogalactose content varies within a range of 15.31% to 18.98%. The molecular weight distribution of G. chouae polysaccharides ranged from 1.85 to 2.09 × 10³ kDa. The apparent viscosity of the LYG and BHW polysaccharides was relatively high, whereas that of RZ and ND was comparatively low. The gel strength displayed a similar trend. BHW and LYG exhibited solid-like behavior, while ND, RZ, and BH demonstrated liquid-like characteristics at low frequencies. The redundancy analysis (RDA) analysis revealed a positive correlation between the texture profile analysis (TPA) characteristics and anhydrogalactose. The study could provide recommendations for the diverse applications of G. chouae polysaccharides derived from different geographical regions.

We have successfully identified the transcription factor Cmr1 from the fungus Aureobasidium pullulans Hit-lcy3T, which regulates melanin biosynthesis genes. Bioinformatics analysis revealed that the Cmr1 gene encodes a protein of 945 amino acids, containing two Cys₂His₂ zinc finger domains and a Zn(II)₂Cys₆ binuclear cluster domain located at the N-terminus of Cmr1. To investigate the function of the Cmr1 gene, we performed gene knockout and overexpression experiments. Our results showed that Cmr1 is a key regulator of melanin synthesis in Hit-lcy3^T, and its absence caused developmental defects. Conversely, overexpression of Cmr1 significantly increased the number of chlamydospores in Hit-lcy3^T and improved melanin production. RT-qPCR analysis further revealed that overexpression of Cmr1 enhanced the expression of several genes involved in melanin biosynthesis, including Cmr1, PKS, SCD1, and THR1. Melanin extracted from the Hit-lcy3^T was characterized using UV and IR spectroscopy. Furthermore, we assessed the antioxidant properties of Hit-lcy3^T melanin and found that it possesses strong scavenging activity against DPPH·, ABTS·, and OH·, but weaker activity against O₂⁻·. These findings suggest that Hit-lcy3^T melanin holds promise for future development as a functional food additive.

Cytochalasans, with diverse structures and pharmacological activities, are a class of compounds containing isoindolinone moieties fused to the tricyclic or tetracyclic ring system. Chaetoglobosin A (cheA), mainly produced by Chaetomium globosum, is the most abundant cytochalasan. However, limited understanding of transcriptional regulation of morphological development and cheA biosynthesis in C. globosum has hindered cheA application in agriculture and biomedical field. This study examined the regulatory role of CgVeA gene in C. globosum. CgVeA had significant effect on secondary metabolites production in C. globosum, similar to that reported in other filamentous fungi. Inactivation of CgVeA caused an obvious decrease in cheA production from 51.32 to 19.76 mg/L under dark conditions. In contrast, CgVeA overexpression resulted in a dramatic increase in cheA production, reaching 206.59 mg/L under light conditions, which was higher than that noted under dark condition. The RT-qPCR results confirmed that CgVeA, as a light responsive regulator, positively regulated cheA biosynthesis by controlling the expression of core genes of the cheA biosynthetic gene cluster and other relevant regulators. Electrophoretic mobility shift assays proved that CgVeA directly regulated LaeA, cheR, and p450, and indirectly regulated PKS. Moreover, CgVeA had a significant effect on the regulation of asexual spores production. When compared with wild-type C. globosum, CgVeA-silenced and CgVeA overexpression mutants presented remarkable differences in sporulation, irrespective of light or dark condition. Besides, CgVeA expression was speculated to negatively regulate spore formation. These findings illustrated the regulatory mechanism of a hypothetical global regulator, CgVeA, in C. globosum, suggesting its potential application in industrial-scale cheA biosynthesis.