Evaluation of Sufu Fermented Using Mucor racemosus M2: Biochemical, Textural, Structural and Microbiological Properties

Development and characterization of starch/polyvinyl alcohol active films with slow-release property by utilizing Mucorracemosus Fresenius mycelium to load with clove essential oil

The controlled release active packaging film represents a novel technology that always can effectively slow down the release of active agents, extending their efficacy. Mucorracemosus Fresenius (MF) mycelium was prepared and used as an adsorption carrier to load clove essential oil (CEO). The CEO/MF complexes were incorporated into the starch/polyvinyl alcohol (Starch/PVA) matrix to develop active films. The effects of MF content on the films' properties were investigated. MF exhibited the internal hollow structure with diaphragm inside and showed antioxidant activity. The adsorption rate of MF on CEO was 238.09 %. As MF increased, the tensile strength, water contact angle and gas barrier properties (water vapor and oxygen) of the films containing CEO enhanced. The release rate of CEO from the films into food simulant (10 % ethanol) slowed down significantly with increasing of MF. Compared to the film without MF, the film with highest MF delayed 33 h to reach equilibrium. The films with different content of MF showed different antioxidant and antibacterial activities, and different preservation effects on shrimp. It showed a great prospect to develop controlled release active films by utilizing MF mycelium as an adsorption material, which enriched the technical solutions for developing controlled release active packaging films.

The Fermentation Law of Biogenic Amines in the Pre-Fermentation Process Is Revealed by Correlation Analysis

Sufu is a traditional Chinese condiment with a distinctive flavor. The umami characteristics are primarily attributed to the hydrolysis of proteins, which produces amino acids and biogenic amines (BAs). Excessive levels of BAs can pose health risks, leading to adverse effects, such as headaches, digestive disorders, and abnormal blood pressure. However, the mechanisms leading to the formation of BAs in fermented bean curd remain insufficiently explored. To explore this phenomenon, an analysis was conducted on the texture, physicochemical properties, and BA content dynamic changes of sufu, fermented with Mucor racemosus, at different intervals, by high-performance liquid chromatography-mass spectrometry (HPLC-MS). During the fermentation process, the total biogenic amines exhibited a downward trend, with levels decreasing from 60.66 to 38.19 mg/kg. Spermidine, spermine, and cadaverine were identified as the main biogenic amines produced during the fermentation process. At 0 h and 24 h, spermidine levels significantly decreased (p < 0.05), but no significant differences were observed at 48 h and 72 h. At 96 h, spermidine levels significantly decreased again (p < 0.05). There was a positive relationship between the bioamines and water content and a negative correlation with soluble protein levels. Additionally, low pH inhibits the formation of BAs, while a soft texture was found to increase their production. The results of this study also confirmed the mechanism of BAs formation. These findings offer valuable insights into the safety and quality control of Mouding sufu by clarifying the BA dynamics during pre-fermentation.

Assisted Fermentation by a Modified Bacillus subtilis Strain Producing Protease Improved the Quality of Sufu

Traditionally fermented sufu is popular because of its flavor, abundance of nutrients, and long shelf life. However, traditional sufu is difficult to produce via industrial processes because of dominant microorganism attenuation during fermentation. Herein, specific protease-producing strains were isolated from traditional sufu. After strain identification, mutation, and domestication, the strains were applied in fermentation. The taste, texture, and nutrient and flavor components of the fermentation products were investigated via organoleptic, textural HPLC and HS-GC-IMS analyses. Results revealed that Bacillus subtilis (DF1) and the derived strains DF1v and DF1vd had increased protease activity relative to other strains. When these strains were applied for sufu fermentation, the production period significantly shortened to 6-8 days for pehtzes and to 20-26 days for postripening. The nutrient and flavor compound composition of both sufu pehtzes and products improved, including increases in water-soluble proteins, amino acids, and substances with beany and umami aromas and decreases in nonbeneficial biogenic amines and moldy odor-imparting substances. Among the strains, DF1vd showed the greatest benefits in sufu-assisted fermentation. In summary, a modified Bacillus subtilis strain (DF1vd) producing protease was isolated, which improved the nutrient profile and flavor of sufu and shortened the production period.

Classes and phyla of the kingdom Fungi

Fungi are one of the most diverse groups of organisms with an estimated number of species in the range of 2–3 million. The higher-level ranking of fungi has been discussed in the framework of molecular phylogenetics since Hibbett et al., and the definition and the higher ranks (e.g., phyla) of the ‘true fungi’ have been revised in several subsequent publications. Rapid accumulation of novel genomic data and the advancements in phylogenetics now facilitate a robust and precise foundation for the higher-level classification within the kingdom. This study provides an updated classification of the kingdom Fungi, drawing upon a comprehensive phylogenomic analysis of Holomycota, with which we outline well-supported nodes of the fungal tree and explore more contentious groupings. We accept 19 phyla of Fungi, viz. Aphelidiomycota, Ascomycota, Basidiobolomycota, Basidiomycota, Blastocladiomycota, Calcarisporiellomycota, Chytridiomycota, Entomophthoromycota, Entorrhizomycota, Glomeromycota, Kickxellomycota, Monoblepharomycota, Mortierellomycota, Mucoromycota, Neocallimastigomycota, Olpidiomycota, Rozellomycota, Sanchytriomycota, and Zoopagomycota. In the phylogenies, Caulochytriomycota resides in Chytridiomycota; thus, the former is regarded as a synonym of the latter, while Caulochytriomycetes is viewed as a class in Chytridiomycota. We provide a description of each phylum followed by its classes. A new subphylum, Sanchytriomycotina Karpov is introduced as the only subphylum in Sanchytriomycota. The subclass Pneumocystomycetidae Kirk et al. in Pneumocystomycetes, Ascomycota is invalid and thus validated. Placements of fossil fungi in phyla and classes are also discussed, providing examples.

Quality and flavor development of solid-state fermented surimi with Actinomucor elegans: A perspective on the impacts of carbon and nitrogen sources

The influence of four carbon and nitrogen substrates on the quality and flavor of a novel surimi-based product fermented with Actinomucor elegans (A. elegans) was investigated, with a focus on carbon and nitrogen catabolite repression. The results showed that the substrate significantly affected mycelial growth, enzyme activities, and the metabolites of A. elegans. Although glucose significantly promoted A. elegans growth by 116.69%, it decreased enzyme secretion by 69.79% for α-amylase and 59.80% for protease, most likely by triggering the carbon catabolite repression pathway. Starch, soy protein, and wheat gluten substantially affected the textural properties of the fermented surimi. Furthermore, wheat gluten significantly promoted the protease activity (102.70%) and increased protein degradation during surimi fermentation. The fishy odor of surimi was alleviated through fermentation, and a correlation between the volatile compounds and A. elegans metabolism was observed. These results explore fermentation substrates in filamentous fungi metabolism from a catabolite repression perspective.