Effect of key regulators in augmenting transcriptional expression of Transglutaminase in Streptomyces mobaraensis

Recent insights into bonding technologies in restructured meat production: A review

Restructuring meat products is one way of improving material utilization and economic efficiency. In this process of combining meat pieces or granules to form larger pieces of meat, the additives and processing techniques employed in bonding the restructured meat play crucial roles in the formation of the structure and appearance of the meat while simultaneously reducing nutrient and water loss and enhancing flavor. This study reviews the adhesives commonly used in meat recombination technology, including transglutaminase, glucono-delta-lactone, fibrin, gelatin, and gel emulsifiers such as hydrophilic colloid, phosphate, starch, and cellulose. Additionally, processing technologies such as high-pressure, ultrasonic, vacuum-assisted, microwave, and three-dimensional printing are discussed, with emphasis on their principles, properties, functionalities, and safety. The study further summarizes the application and research progress of various bonding techniques in restructured meat. It analyzes the advantages, challenges, and development prospects of these techniques to provide support for further research in this field.

The Complete Genomic Sequence of Microbial Transglutaminase Producer, Streptomyces mobaraensis DSM40587

Actinomycetes are remarkable natural sources of active natural molecules and enzymes of considerable industrial value. Streptomyces mobaraensis is the first microorganism found to produce transglutaminase with broad industrial applications. Although transglutaminase in S. mobaraensis has been well studied over the past three decades, the genome of S. mobaraensis and its secondary metabolic potential were poorly reported. Here, we presented the complete genome of S. mobaraensis DSM40587 obtained from the German Collection of Microorganisms and Cell Cultures GmbH. It contains a linear chromosome of 7,633,041 bp and a circular plasmid of 23,857 bp. The chromosome with an average GC content of 73.49% was predicted to harbour 6683 protein-coding genes, seven rRNA and 69 tRNA genes. Comparative genomic analysis reveals its meaningful genomic characterisation. A comprehensive bioinformatics investigation identifies 35 putative BGCs (biosynthesis gene clusters) involved in synthesising various secondary metabolites. Of these, 13 clusters showed high similarity (> 55%) to known BGCs coding for polyketides, nonribosomal peptides, hopene, RiPP (Ribosomally synthesized and post-translationally modified peptides), and others. Furthermore, these BGCs with over 65% similarity to the known BGCs were analysed in detail. The complete genome of S. mobaraensis DSM40587 reveals its capacity to yield diverse bioactive natural products and provides additional insights into discovering novel secondary metabolites.

The Potential Harmful Effects of Genetically Engineered Microorganisms (GEMs) on the Intestinal Microbiome and Public Health

Gut luminal dysbiosis and pathobiosis result in compositional and biodiversified alterations in the microbial and host co-metabolites. The primary mechanism of bacterial evolution is horizontal gene transfer (HGT), and the acquisition of new traits can be achieved through the exchange of mobile genetic elements (MGEs). Introducing genetically engineered microbes (GEMs) might break the harmonized balance in the intestinal compartment. The present objectives are: 1. To reveal the role played by the GEMs' horizontal gene transfers in changing the landscape of the enteric microbiome eubiosis 2. To expand on the potential detrimental effects of those changes on the human genome and health. A search of articles published in PubMed/MEDLINE, EMBASE, and Scielo from 2000 to August 2023 using appropriate MeSH entry terms was performed. The GEMs' horizontal gene exchanges might induce multiple human diseases. The new GEMs can change the long-term natural evolution of the enteric pro- or eukaryotic cell inhabitants. The worldwide regulatory authority's safety control of GEMs is not enough to protect public health. Viability, biocontainment, and many other aspects are only partially controlled and harmful consequences for public health should be avoided. It is important to remember that prevention is the most cost-effective strategy and primum non nocere should be the focus.

Identification of multiple regulatory genes involved in TGase production in Streptomyces mobaraensis DSM 40587

Microbial transglutaminase (TGase) is a protein that is secreted in a mature form and finds wide applications in meat products, tissue scaffold crosslinking, and textile engineering. Streptomyces mobaraensis is the only licensed producer of TGase. However, increasing the production of TGase using metabolic engineering and heterologous expression approaches has encountered challenges in meeting industrial demands. Therefore, it is necessary to identify the regulatory networks involved in TGase biosynthesis to establish a stable and highly efficient TGase cell factory. In this study, we employed a DNA-affinity capture assay and mass spectrometry analysis to discover several transcription factors. Among the candidates, eight were selected and found to impact TGase biosynthesis. Notably, SMDS_4150, an AdpA-family regulator, exhibited a significant influence and was hence named AdpA Sm . Through electrophoretic mobility shift assays, we determined that AdpA Sm regulates TGase biosynthesis by directly repressing the transcription of tg and indirectly inhibiting the transcription of SMDS_3961. The latter gene encodes a LytR-family positive regulator of TGase biosynthesis. Additionally, AdpA Sm exhibited negative regulation of its own transcription. To further enhance TGase production, we combined the overexpression of SMDS_3961 with the repression of SMDS_4150, resulting in a remarkable improvement in TGase titer from 28.67 to 52.0 U/mL, representing an 81.37% increase. This study establishes AdpA as a versatile regulator involved in coordinating enzyme biosynthesis in Streptomyces species. Furthermore, we elucidated a cascaded regulatory network governing TGase production.

Transglutaminase in Foods and Biotechnology

Stabilization and reusability of enzyme transglutaminase (TGM) are important goals for the enzymatic process since immobilizing TGM plays an important role in different technologies and industries. TGM can be used in many applications. In the food industry, it plays a role as a protein-modifying enzyme, while, in biotechnology and pharmaceutical applications, it is used in mediated bioconjugation due to its extraordinary crosslinking ability. TGMs (EC 2.3.2.13) are enzymes that catalyze the formation of a covalent bond between a free amino group of protein-bound or peptide-bound lysine, which acts as an acyl acceptor, and the γ-carboxamide group of protein-bound or peptide-bound glutamine, which acts as an acyl donor. This results in the modification of proteins through either intramolecular or intermolecular crosslinking, which improves the use of the respective proteins significantly.

Improved Productivity of Streptomyces mobaraensis Transglutaminase by Regulating Zymogen Activation

Streptomyces mobaraensis transglutaminase (TGase) is extracellularly expressed as a zymogen and then activated by TGase-activating protease (TAP). In this study, we reported the strategy for improving TGase production via the regulation of TAP activity in S. mobaraensis. First, we analyzed the effects of three inorganic nitrogen sources on TGase production. With 30 mM nitrogen content, the time to the peak of TGase activity induced by (NH₄)₂SO₄ or NH₄Cl was 72 h, 12 h earlier than that of the fermentation without adding NH₄⁺. SDS-PAGE analysis indicated that NH₄⁺ accelerated the TGase activation in S. mobaraensis. Then, we examined the effect of NH₄⁺ on TAP biosynthesis using a TGase-deficient S. mobaraensis strain. It showed that NH₄⁺ enhanced the TAP activity at the early stage of the fermentation, which was dependent on the concentration and time of NH₄⁺ addition. Last, the yield and productivity of S. mobaraensis TGase were increased by 1.18-fold and 2.1-fold, respectively, when optimal NH₄⁺ addition (60 mM and 12 h) was used. The fermentation period was shortened from 84 to 48 h. The NH₄⁺ addition also increased the storage stability of crude enzyme at room temperature. These findings will benefit the TGase production and its activation mechanism in S. mobaraensis.