Enhancement of transglutaminase production in Streptomyces mobaraensis DSM 40587 by non-nutritional stress conditions: Effects of heat shock, alcohols, and salt treatments

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.

Efficient biosynthesis of transglutaminase in Streptomyces mobaraensis via systematic engineering strategies

Transglutaminases (TGases) have been widely used in food, pharmaceutical, biotechnology, and other industries because of their ability to catalyze deamidation, acyl transfer, and crosslinking reactions between Ƴ-carboxamide groups of peptides or protein-bound glutamine and the Ɛ-amino group of lysine. In this study, we demonstrated an efficient systematic engineering strategy to enhance the synthesis of TGase in a recombinant Streptomyces mobaraensis smL2020 strain in a 1000-L fermentor. Briefly, the enzymatic properties of the TGase TGL2020 from S. mobaraensis smL2020 and TGase TGLD from S. mobaraensis smLD were compared to obtain the TGase TGLD with perfected characteristics for heterologous expression in a recombinant S. mobaraensis smL2020ΔTG without the gene tgL 2020. Through multiple engineering strategies, including promoter engineering, optimizing the signal peptides and recombination sites, and increasing copies of the expression cassettes, the final TGLD activity in the recombinant S. mobaraensis smL2020ΔTG: (PL2020-spL2020-protgLD-tgLD)2 (tgL2020and BT1) reached 56.43 U/mL and 63.18 U/mL in shake flask and 1000-L fermentor, respectively, which was the highest reported to date. With the improvement of expression level, the application scope of TGLD in the food industry will continue to expand. Moreover, the genetic stability of the recombinant strain maintained at more than 20 generations. These findings proved the feasibility of multiple systematic engineering strategies in synthetic biology and provided an emerging solution to improve biosynthesis of industrial enzymes.

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.