Characterization of a lactic acid bacteria using branched-chain amino acid transaminase and protease from Jinhua Ham and application in myofibrillar protein model

Identification of proteolytic bacteria from Yunnan fermented foods and their use to reduce the allergenicity of β-lactoglobulin

Beta-lactoglobulin (β-LG) is considered to be the major allergenic protein in milk. Lactic acid bacteria (LAB) possess a protein hydrolysis system that holds great promise for hydrolyzing β-LG and reducing its allergenicity. Therefore, this study aimed to screen LAB with β-LG hydrolysis activity from Yunnan traditional fermented foods. The results showed that Pediococcus pentosaceus C1001, Pediococcus acidilactici E1601-1, and Lactobacillus paracasei E1601-2, could effectively hydrolyze β-LG and further reduce its sensitization (more than 40%). All 3 lactic acid bacteria hydrolyzed β-LG allergenic fragments V41-K60 and L149-I162. Moreover, they encode a variety of genes related to proteolysis, such as aminopeptidase pepC and pepN, proline peptidase pepIP and endopeptidase pepO, and L. paracasei E1601-2 contains extracellular protease coding gene prtP. And they encode a variety of genes associated with hydrolyzed proteins. The 3 strains screened in this study can be used to develop hypoallergenic dairy products.

Fungal-Bacterial Mutualism: Species and Strain-Dependent Simultaneous Modulation of Branched-Chain Esters and Indole Derivatives in Fermented Sausages through Metabolite Cross-Feeding

The precise impact of species and strain diversity on fungal-bacterial interactions and the overall community functioning has remained unclear. First, our study revealed how Debaryomyces hansenii influences diverse bacteria to accumulate key metabolites in a simulated fermented food system. For flavor, D. hansenii promoted the accumulation of branched-chain esters in Staphylococcus xylosus by promoting growth and facilitating the precursor branched-chain acids transformations but hindered the accumulation of Staphylococcus equorum. Furthermore, fungal-bacterial interactions displayed diversity among S. equorum strains. For bioactive compounds, species and strain diversity of lactic acid bacteria (LAB) also influences the production of indole derivatives. Then, we investigated specific metabolic exchanges under reciprocal interaction. Amino acids, rather than vitamins, were identified as the primary drivers of the bacterial growth promotion. Moreover, precursor transformations by D. hansenii played a significant role in branched-chain esters production. Finally, a synthetic community capable of producing high concentrations of branched-chain esters and indole derivatives was successfully constructed. These results provide valuable insights into understanding and designing synthetic communities for fermented sausages.

The Contribution of Microorganisms to the Quality and Flavor Formation of Chinese Traditional Fermented Meat and Fish Products

Guizhou sour meat and sour fish, Chaoshan fish sauce, Sichuan sausage and bacon, Cantonese sausage, Jinhua ham, and Xinjiang air-dried beef are eight representatives of Chinese traditional fermented meat and fish products (FMFPs), which are favored by Chinese consumers due to their high nutritional value and quality. The quality of the spontaneously fermented Chinese traditional FMFP is closely correlated with microorganisms. Moreover, the dominant microorganisms are significantly different due to regional differences. The effects of microorganisms on the texture, color, flavor, nutrition, functional properties, and safety of Chinese traditional FMFPs have not been not fully described. Additionally, metabolic pathways for flavor formation of Chinese traditional FMFPs have not well been summarized. This article describes the seven characteristic Chinese traditional FMFPs and correlated dominant microorganisms in different regions of China. The effects of microorganisms on the texture, color, and flavor of Chinese traditional FMFPs are discussed. Furthermore, the metabolic pathways of microbial regulation of flavor formation in Chinese traditional FMFPs are proposed. This work provides a theoretical basis for improvement of Chinese traditional FMFPs by inoculating functional microorganisms isolated from Chinese traditional fermented foods.

Role of microbiota and its ecological succession on flavor formation in traditional dry-cured ham: a review

Traditional dry cured ham (DCH) is favored by consumers for its distinctive flavor, derived from an array of volatile organic compounds (VOCs). Microbiota play a pivotal role in the formation of VOCs. To fully comprehend the pathway by which the microbiota enhance the flavor quality of DCH, it is imperative to elucidate the flavor profile of DCH, the structural and metabolic activities of the microbiota, and the intricate relationship between microbial and VOCs. Thus far, the impact of microbiota on the flavor profile of DCH has not been comprehensively discussed or reviewed, and the succession of bacteria, especially at distinct phases of processing, has not been adequately summarized. This article aims to encapsulate the considerable potential of ferments in shaping the flavor characteristics of DCH, while elucidating the underlying mechanisms through which VOCs are generated in hams via microbial metabolism. Throughout the various stages of DCH processing, the composition of microbiota undergoes dynamic changes. Furthermore, they directly participate in the formation of VOCs in DCH through the catabolism of amino acids, metabolism of fatty acids, and the breakdown of carbohydrates. Several microorganisms, including Lactobacillus, Penicillium, Debaryomyces, Pediococcus, and Staphylococcus, exhibit considerable potential as fermenters in ham production.

Research progress on branched-chain amino acid aminotransferases

Branched-chain amino acid aminotransferases, widely present in natural organisms, catalyze bidirectional amino transfer between branched-chain amino acids and branched-chain α-ketoacids in cells. Branched-chain amino acid aminotransferases play an important role in the metabolism of branched-chain amino acids. In this paper, the interspecific evolution and biological characteristics of branched-chain amino acid aminotransferases are introduced, the related research of branched-chain amino acid aminotransferases in animals, plants, microorganisms and humans is summarized and the molecular mechanism of branched-chain amino acid aminotransferase is analyzed. It has been found that branched-chain amino acid metabolism disorders are closely related to various diseases in humans and animals and plants, such as diabetes, cardiovascular diseases, brain diseases, neurological diseases and cancer. In particular, branched-chain amino acid aminotransferases play an important role in the development of various tumors. Branched-chain amino acid aminotransferases have been used as potential targets for various cancers. This article reviews the research on branched-chain amino acid aminotransferases, aiming to provide a reference for clinical research on targeted therapy for various diseases and different cancers.

Non-gene-editing microbiome engineering of spontaneous food fermentation microbiota-Limitation control, design control, and integration

Non-gene-editing microbiome engineering (NgeME) is the rational design and control of natural microbial consortia to perform desired functions. Traditional NgeME approaches use selected environmental variables to force natural microbial consortia to perform the desired functions. Spontaneous food fermentation, the oldest kind of traditional NgeME, transforms foods into various fermented products using natural microbial networks. In traditional NgeME, spontaneous food fermentation microbiotas (SFFMs) are typically formed and controlled manually by the establishment of limiting factors in small batches with little mechanization. However, limitation control generally leads to trade-offs between efficiency and the quality of fermentation. Modern NgeME approaches based on synthetic microbial ecology have been developed using designed microbial communities to explore assembly mechanisms and target functional enhancement of SFFMs. This has greatly improved our understanding of microbiota control, but such approaches still have shortcomings compared to traditional NgeME. Here, we comprehensively describe research on mechanisms and control strategies for SFFMs based on traditional and modern NgeME. We discuss the ecological and engineering principles of the two approaches to enhance the understanding of how best to control SFFM. We also review recent applied and theoretical research on modern NgeME and propose an integrated in vitro synthetic microbiota model to bridge gaps between limitation control and design control for SFFM.

Effects of the addition of leucine on flavor and quality of sausage fermented by Lactobacillus fermentum YZU-06 and Staphylococcus saprophyticus CGMCC 3475

Methyl-branched aldehydes, especially 3-methylbutanal, have been reported to be perceived either as a malty or as a nutty/chocolate-like aroma and were considered an important flavor contributor in fermented meat products. Decomposition of leucine (Leu) by branched-chain amino acid transaminase (BACT) is a crucial step in the metabolism of Leu to 3-methylbutanal. This study was conducted to explore the effects of mixed-starter culture (Lactobacillus fermentum YZU-06 and Staphylococcus saprophyticus CGMCC 3475) and addition of Leu (0, 1, and 3 mM) on the flavor and quality of fermented sausages. The pH, water activity, texture profile analysis, color, counts of lactic acid bacteria (LAB) and staphylococci, peptide, and flavor compounds were detected during fermentation. The results showed that the starter culture group increased hardness, elasticity, the counts of LAB and staphylococci, peptide content, volatile flavor compounds, as well as the sensorial scores of sausage, while decreasing pH, a _w , and L* and b* values compared with the non-inoculation group. The mixed starter of adding with 3 mM Leu enhanced the content of 3-methylbutanal and overall flavor of fermented sausages. It is applicable to directionally produce methyl-branched aldehydes and improve the overall quality of fermented sausage by the addition of Leu and using starter of L. fermentum YZU-06 and S. saprophyticus CGMCC 3475.