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In fermented foods, acetic acid bacteria (AAB), kinds of bacteria with a long history of utilization, contribute to safety, nutritional, and sensory properties primarily through acetic acid fermentation. AAB are commonly found in various fermented foods such as vinegar, sour beer, fermented cocoa and coffee beans, kefir beverages, kombucha, and sourdough. They interact and cooperate with a variety of microorganisms, resulting in the formation of diverse metabolites and the production of fermented foods with distinct flavors. Understanding the interactions between AAB and other microbes is crucial for effectively controlling and utilizing AAB in fermentation processes. However, these microbial interactions are influenced by factors such as strain type, nutritional conditions, ecological niches, and fermentation duration. In this review, we examine the relationships and research methodologies of microbial interactions and interaction studies between AAB and yeasts, lactic acid bacteria (LAB), and bacilli in different food fermentation processes involving these microorganisms. The objective of this review is to identify key interaction models involving AAB and other microorganisms. The insights gained will provide scientific guidance for the effective utilization of AAB as functional microorganisms in food fermentation processes. [ABSTRACT FROM AUTHOR]

Polyunsaturated fatty acids (PUFAs) have beneficial roles in a variety of human pathologies and disorders. Owing to the limited source of PUFAs in animals and plants, microorganisms, especially fungi, have become a new source of PUFAs. In fungi, fatty acid desaturases (F-FADS) are the main enzymes that convert saturated fatty acids (SFAs) into PUFAs. Their catalytic activities and substrate specificities, which are directly dependent on the structure of the FADS proteins, determine their efficiency to convert SFAs to PUFAs. Catalytic mechanisms underlying F-FADS activities can be determined from the findings of the relationship between their structure and function. In this review, the advances made in the past decade in terms of catalytic activities and substrate specificities of the fungal FADS cluster are summarized. The relationship between the key domain(s) and site(s) in F-FADS proteins and their catalytic activity is highlighted, and the FADS cluster is analyzed phylogenetically. In addition, subcellular localization of F-FADS is discussed. Finally, we provide prospective crystal structures of F-FADSs. The findings may provide a reference for the resolution of the crystal structures of F-FADS proteins and facilitate the increase in fungal PUFA production for human health. [ABSTRACT FROM AUTHOR]

Abstract Background Conjugated linoleic acid (CLA) has many well-documented beneficial physiological effects. Due to the insufficient natural supply of CLA and low specificity of chemically produced CLA, an effective and isomer-specific production process is required for medicinal and nutritional purposes. Results The linoleic acid isomerase gene from Propionibacterium acnes was expressed in Yarrowia lipolytica Polh. Codon usage optimization of the PAI and multi-copy integration significantly improved the expression level of PAI in Y. lipolytica. The percentage of trans-10, cis-12 CLA was six times higher in yeast carrying the codon-optimized gene than in yeast carrying the native gene. In combination with multi-copy integration, the production yield was raised to approximately 30-fold. The amount of trans-10, cis-12 CLA reached 5.9% of total fatty acid yield in transformed Y. lipolytica. Conclusions This is the first report of production of trans-10, cis-12 CLA by the oleaginous yeast Y. lipolytica, using glucose as the sole carbon source through expression of linoleic acid isomerase from Propionibacterium acnes.

Introduction: The starter used in solid-state fermentation (SSF) vinegar, known as seed Pei is a microbial inoculant from the previous batch that is utilized during the acetic acid fermentation stage. The seed Pei , which has a notable impact on vinegar fermentation and flavor, is under-researched with comparative studies on microorganisms., Methods: Herein metagenomics was employed to reveal the microbes and their potential metabolic functions of four seed Pei from three regions in China., Results: The predominant microbial taxa in all four starters were bacteria, followed by viruses, eukaryotes, and archaea, with Lactobacillus sp. or Acetobacter sp. as main functional taxa. The seed Pei used in Shanxi aged vinegar (SAV) and Sichuan bran vinegar (SBV) exhibited a higher similarity in microbial composition and distribution of functional genes, while those used in two Zhenjiang aromatic vinegar (ZAV) differed significantly. Redundancy analysis (RDA) of physicochemical factors and microbial communities indicated that moisture content, pH, and reducing sugar content are significant factors influencing microbial distribution. Moreover, seven metagenome-assembled genomes (MAGs) that could potentially represent novel species were identified., Conclusions: There are distinctions in the microbiome and functional genes among different seed Pei . The vinegar starters were rich in genes related to carbohydrate metabolism. This research provides a new perspective on formulating vinegar fermentation starters and developing commercial fermentation agents for vinegar production., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Han, Yang, Guo, Chen, Dai, Zhu, Wang, Yu, Wang, Liu, Rong and Yu.)