Enhancement of transglutaminase production in Streptomyces mobaraensis as achieved by treatment with excessive MgCl2

Multi-omics investigation of high-transglutaminase production mechanisms in Streptomyces mobaraensis and co-culture-enhanced fermentation strategies

Transglutaminase (TGase) has been widely applied in the food industry. However, achieving high-yield TGase production remains a challenge, limiting its broader industrial application. In this study, a high-yield strain with stable genetic traits was obtained through UV-ARTP combined mutagenesis, achieving a maximum TGase activity of 13.77 U/mL, representing a 92.43% increase. Using this strain as a forward mutation gene pool, comparative genomic research identified 95 mutated genes, which were mostly due to base substitutions that led to changes in codon usage preference. Transcriptomic analysis revealed significant expression changes in 470 genes, with 232 upregulated and 238 downregulated genes. By investigating potential key regulatory factors, comprehensive analysis indicated that changes in codon usage preference, amino acid metabolism, carbon metabolism, protein export processes, TGase activation, and spore production pathways collectively contributed to the enhancement of TGase activity. Subsequently, the in vitro activation efficiency of TGase was further improved using co-cultivation techniques with neutral proteases secreted by Bacillus amyloliquefaciens CICC10888, and a TGase activity of 16.91 U/mL was achieved, accounting for a 22.71% increase. This study provides a comprehensive understanding of the mechanisms underlying high-yield TGase production and valuable insights and data references for future research.

Integrated strategies for efficient production of Streptomyces mobaraensis transglutaminase in Komagataella phaffii

Transglutaminase (TGase) from Streptomyces mobaraensis commonly used to improve protein-based foods due to its unique enzymatic reactions, which imply considerable attention in its production. Recently, TGase exhibit broad market potential in non-food industries. However, achieving efficient synthesis of TGase remains a significant challenge. Herein, we achieved a substantial amount of a fully functional and kinetically stable TGase produced by Komagataella phaffii (Pichia pastoris) using multiple strategies including Geneticin (G418) screening, combinatorial mutations, promoter optimization, and co-expression. The active TGase expression reached a maximum of 10.1 U mL-1 in shake flask upon 96 h of induction, which was 3.8-fold of the wild type. Also, the engineered strain exhibited a 6.4-fold increase in half-life and a 2-fold increase in specific activity, reaching 172.67 min at 60 °C (t1/2(60 °C)) and 65.3 U mg-1, respectively. Moreover, the high-cell density cultivation in 5-L fermenter was also applied to test the productivity at large scale. Following optimization at a fermenter, the secretory yield of TGase reached 47.96 U mL-1 in the culture supernatant. Given the complexity inherent in protein expression and secretion, our research is of great significance and offers a comprehensive guide for improving the production of a wide range of heterologous proteins.

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.

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.

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

Transglutaminase forms isopeptide bonds in proteins which are helpful in various industrial applications. However, low productivity and high cost are the major bottlenecks for industrial Transglutaminase production. The present study describes the regulatory mechanism of microbial Transglutaminase (MTGase) biosynthesis from Streptomyces mobaraensis and the effect of key regulators to maximize production. The transcriptional responses under the effect of various key modulators of MTGasebiosynthesis were evaluated. Productivity of MTGase with novel biosynthesis approach by regulators augmentation was correlated by transcriptional profiling. The optimization by key modulators by combinational supplementation led to 2-fold rise in activity. The functional attributes, the copy number of MTGase gene and relative changes were assessed by Real-Time quantitative PCR. Protease, MgCl₂, CTAB induced upregulation, whereas PMSF, NaF and bleomycin sulphate showed inhibitory action on MTGase production and activity. The optimization by combinational supplementation of key modulators led to 4.27-fold increase (6.11 IU/mL) in production.

Enhanced Production of Transglutaminase in Streptomyces mobaraensis through Random Mutagenesis and Site-Directed Genetic Modification

Streptomyces transglutaminase (TGase) is widely used to improve food texture properties. In this study, random mutagenesis and site-directed genetic modification were used to improve the production of TGase in Streptomyces mobaraensis. First, S. mobaraensis DSM40587 (smWT) was subjected to atmospheric and room-temperature plasma mutagenesis, and then a mutant (smY2019) with a 5.5-fold increase in TGase yield was screened from approximately 3000 × 25 (round) mutants. Compared to smWT, smY2019 exhibits a 3.2-fold higher TGase mRNA level and two site mutations within the -10 region of the TGase promoter. The recombinant expression analysis in the TGase-deficient S. mobaraensis suggests that the mutated TGase promoter is more robust than the wild-type one. Finally, we integrated two additional TGase expression cassettes into the smY2019 genome, yielding the recombinant strain smY2019-3C with a 103% increase in TGase production compared to smY2019. The smY2019-3C strain with 40 U/mL of TGase yield could be a suitable candidate for the industrial production of TGase.

Mechanisms of response to pH shock in microbial fermentation

The following review highlights pH shock, a novel environmental factor, as a tool for the improvement of fermentation production. The aim of this review is to introduce some recent original studies on the enhancement of microbial fermentation production by pH shock. Another purpose of this review is to improve the understanding of the processes that underlie physiological and genetic differences, which will facilitate future research on the improvement of fermentation production and reveal the associated molecular mechanisms. This understanding will simultaneously promote the application of this strategy to other microbial fermentation systems. Furthermore, improvement of the cellular tolerance of genetically engineered bacteria can also be a new field of research in the future to enhance fermentation production.

Utilization of agro-industrial waste for production of Transglutaminase from Streptomyces mobaraensis

This work studied the production of Transglutaminase (TGase) using wheat bran as carbon source. The medium components and culture conditions were optimized by statistical Box-Behnken response surface methodology. The release of active Transglutaminase was enhanced by adding (i) protease to remove pro-region to make inactive enzyme to active form, (ii) Cetyl trimethyl ammonium bromide (CTAB) which facilitated more secretion. Under finally optimized conditions viz. 5 g wheat bran, protease: 39.14 U, magnesium chloride (MgCl₂): 0.10 M, CTAB: 0.08% and inoculation size: 2% led to 4-fold (12.949 ± 0.061 IU/g) increased TGase production over that of un-optimized conditions. The application of TGase was shown to be useful in effective casein cross-linking.

Streptomyces Differentiation in Liquid Cultures as a Trigger of Secondary Metabolism

Streptomyces is a diverse group of gram-positive microorganisms characterised by a complex developmental cycle. Streptomycetes produce a number of antibiotics and other bioactive compounds used in the clinic. Most screening campaigns looking for new bioactive molecules from actinomycetes have been performed empirically, e.g., without considering whether the bacteria are growing under the best developmental conditions for secondary metabolite production. These screening campaigns were extremely productive and discovered a number of new bioactive compounds during the so-called “golden age of antibiotics” (until the 1980s). However, at present, there is a worrying bottleneck in drug discovery, and new experimental approaches are needed to improve the screening of natural actinomycetes. Streptomycetes are still the most important natural source of antibiotics and other bioactive compounds. They harbour many cryptic secondary metabolite pathways not expressed under classical laboratory cultures. Here, we review the new strategies that are being explored to overcome current challenges in drug discovery. In particular, we focus on those aimed at improving the differentiation of the antibiotic-producing mycelium stage in the laboratory.

Microbial transglutaminase in noodle and pasta processing

Nowadays, there is an aggressive rate in consumption of noodles and pasta products throughout the world. Consumer acceptability and preference of these functional products can be promoted by the discovery of novel knowledge to improve their formulation and quality. The development of fortified-formulations for noodles and pasta products based on microbial transglutaminase (MTGase) can guarantee the shelf life extension with minimum quality losses. The current review focuses on recent trends and future prospects of MTGase utilization in the structural matrix of noodles and pasta products and represents the quality changes of cooking loss, texture, microstructure, color and sensory attributes of the MTGase-incorporated products. Digestibility, nutritional and health aspects of the MTGase-enriched formulations are also reviewed with a vision toward physical functions and safety outcomes of MTGases isolated from new microbial sources. The high potential of MTGase in developing commercial noodles and pasta products is successfully demonstrated. MTGase by modifying the crystallinity or molecular structure via covalent crosslinks between protein molecules strengthens the doughs stability and the textural characteristics of final products with the low- or high-protein flour. Compared with the control samples, the MTGase-supplemented products indicate slower digestion rates and better sensory and cooking properties without any remarkable color instability.

Transglutaminase from newly isolated Streptomyces sp. CBMAI 1617: Production optimization, characterization and evaluation in wheat protein and dough systems

The popularity of transglutaminase (TG) by the food industry and the variation in functionality of this enzyme from different origins, prompted us to isolate and evaluate a high-yielding TG strain. Through the statistical approaches, Plackett-Burman and response surface methodology, a low cost fermentation media was obtained to produce 6.074±0.019UmL^-1 of TG from a novel source; Streptomyces sp. CBMAI 1617 (SB6). Its potential exploitation was compared to commonly used TG, from Streptomyces mobaraensis. Biochemical and FT-IR studies indicated differences between SB6 and commercial TG (Biobond™ TG-M). Additions of TG to wheat protein and flour based doughs revealed that the dough stretching depended on the wheat protein fraction, TG amount and its origin. A higher degree of cross-linking of glutenins and of inclusion of gliadin in the polymers was seen for SB6 as compared to commercial TG. Thus, our results support the potential of SB6 to tailor wheat protein properties within various food applications.