Overproduction of pro-transglutaminase from Streptomyces hygroscopicus in Yarrowia lipolytica and its biochemical characterization

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 Production of a Thermostable Mutant of Transglutaminase by Streptomyces mobaraensis

The transglutaminase (TGase) from Streptomyces mobaraensis is widely used to improve the texture of protein-based foods. However, wild-type TGase is not heat-resistant, which is unfavorable for its application. In this study, we successfully constructed a S. mobaraensis strain that can efficiently produce TGm2, a thermostable mutant of S. mobaraensis TGase. First, S. mobaraensis DSM40587 was subjected to atmospheric room temperature plasma mutagenesis, generating mutant smY2022 with a 12.2-fold increase in TGase activity. Then, based on the double-crossover recombination, we replaced the coding sequence of the TGase with that of TGm2 in smY2022, obtaining the strain smY2022-TGm2. The extracellular TGase activity of smY2022-TGm2 reached 61.7 U/mL, 147% higher than that of smY2022. Finally, the catalytic properties of TGm2 were characterized. The half-life time at 60 °C and specific activity of TGm2 reached 64 min and 71.15 U/mg, 35.6- and 2.9-fold higher than those of the wild-type TGase, respectively. As indicated by SDS-PAGE analysis, TGm2 exhibited demonstrably better protein cross-linking ability than the wild-type TGase at 70 °C, although both enzymes shared a similar ability at 40 °C. With improved enzyme production and thermal stability, smY2022-TGm2 could be a competitive strain for the industrial production of transglutaminase.

Microbiological transglutaminase: Biotechnological application in the food industry

Microbial transglutaminases (mTGs) belong to the family of global TGs, isolated and characterised by various bacterial strains, with the first being Streptomyces mobaraensis. This literature review also discusses TGs of animal and plant origin. TGs catalyse the formation of an isopeptide bond, cross-linking the amino and acyl groups. Due to its broad enzymatic activity, TG is extensively utilised in the food industry. The annual net growth in the utilisation of enzymes in the food processing industry is estimated to be 21.9%. As of 2020, the global food enzymes market was valued at around $2.3 billion USD (mTG market was estimated to be around $200 million USD). Much of this growth is attributed to the applications of mTG, benefiting both producers and consumers. In the food industry, TG enhances gelation and modifies emulsification, foaming, viscosity, and water-holding capacity. Research on TG, mainly mTG, provides increasing insights into the wide range of applications of this enzyme in various industrial sectors and promotes enzymatic processing. This work presents the characteristics of TGs, their properties, and the rationale for their utilisation. The review aims to provide theoretical foundations that will assist researchers worldwide in building a methodological framework and furthering the advancement of biotechnology research.

A Novel Cold-Adapted and High-Alkaline Alginate Lyase with Potential for Alginate Oligosaccharides Preparation

Alginate oligosaccharides (AOs) prepared through enzymatic reaction by diverse alginate lyases under relatively controllable and moderate conditions possess versatile biological activities. But widely used commercial alginate lyases are still rather rare due to their poor properties (e.g., lower activity, worse thermostability, ion tolerance, etc.). In this work, the alginate lyase Alyw208, derived from Vibrio sp. W2, was expressed in Yarrowia lipolytica of food grade and characterized in order to obtain an enzyme with excellent properties adapted to industrial requirements. Alyw208 classified into the polysaccharide lyase (PL) 7 family showed maximum activity at 35 °C and pH 10.0, indicating its cold-adapted and high-alkaline properties. Furthermore, Alyw208 preserved over 70% of the relative activity within the range of 10-55 °C, with a broader temperature range for the activity compared to other alginate-degrading enzymes with cold adaptation. Recombinant Alyw208 was significantly activated with 1.5 M NaCl to around 2.1 times relative activity. In addition, the endolytic Alyw208 was polyG-preferred, but identified as a bifunctional alginate lyase that could degrade both polyM and polyG effectively, releasing AOs with degrees of polymerization (DPs) of 2-6 and alginate monomers as the final products (that is, DPs 1-6). Alyw208 has been suggested with favorable properties to be a potent candidate for biotechnological and industrial applications.

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.

Secretion of Bacillus amyloliquefaciens Transglutaminase from Lactococcus lactis and Its Enhancement of Food Gel Properties

(1) Background: Microbial transglutaminases (MTGase) catalyze protein crosslink. This is useful in the food industry to improve gelation, water holding capacity, and emulsifying capacity during foodstuff manufacturing. The production of MTGase in wild-type strains renders low yield and high costs of downstream purification, limiting its industrial applications. (2) Methods: In this work, MTGase from Bacillus amyloliquefaciens BH072 (BaMTGase) has been heterologously expressed in Lactococcus lactis, using the signal peptide Usp45 to direct the secretion of recombinant BaMTGase out of the cell for easier purification. (3) Results: In these conditions, MTGase was purified with a high yield (48.7 ± 0.2 mg/L) and high enzyme activity (28.6 ± 0.5 U/mg). Next, BaMTGase was tested for industrial applications. Recombinant BaMTGase and commercial MTGase were used for SPI solution crosslinking. BaMTGase formed a harder gel with higher water-holding capacity and a dense and smooth gel microstructure. (4) Conclusions: This work provides an attractive food-grade cell factory for the food industry and offers a suitable chassis for MTGase production.

Customized yeast cell factories for biopharmaceuticals: from cell engineering to process scale up

The manufacture of recombinant therapeutics is a fastest-developing section of therapeutic pharmaceuticals and presently plays a significant role in disease management. Yeasts are established eukaryotic host for heterologous protein production and offer distinctive benefits in synthesising pharmaceutical recombinants. Yeasts are proficient of vigorous growth on inexpensive media, easy for gene manipulations, and are capable of adding post translational changes of eukaryotes. Saccharomyces cerevisiae is model yeast that has been applied as a main host for the manufacture of pharmaceuticals and is the major tool box for genetic studies; nevertheless, numerous other yeasts comprising Pichia pastoris, Kluyveromyces lactis, Hansenula polymorpha, and Yarrowia lipolytica have attained huge attention as non-conventional partners intended for the industrial manufacture of heterologous proteins. Here we review the advances in yeast gene manipulation tools and techniques for heterologous pharmaceutical protein synthesis. Application of secretory pathway engineering, glycosylation engineering strategies and fermentation scale-up strategies in customizing yeast cells for the synthesis of therapeutic proteins has been meticulously described.

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.

Heterologous Expression of Recombinant Transglutaminase in Bacillus subtilis SCK6 with Optimized Signal Peptide and Codon, and Its Impact on Gelatin Properties

Microbial transglutaminases (MTGs) are widely used in the food industry. In this study, the MTG gene of Streptomyces sp. TYQ1024 was cloned and expressed in a food-grade bacterial strain, Bacillus subtilis SCK6. Extracellular activity of the MTG after codon and signal peptide (SP Ync M) optimization was 20 times that of the pre-optimized enzyme. After purification, the molecular weight of the MTG was 38 kDa and the specific activity was 63.75 U/mg. The optimal temperature and pH for the recombinant MTG activity were 50°C and 8.0, respectively. MTG activity increased 1.42- fold in the presence of β-ME and 1.6-fold in the presence of DTT. Moreover, 18% sodium chloride still resulted in 83% enzyme activity, which showed good salt tolerance. Cross-linking gelatin with the MTG increased the strength of gelatin 1.67 times and increased the thermal denaturation temperature from 61.8 to 75.8°C. The MTG also significantly increased the strength and thermal stability of gelatin. These characteristics demonstrated the huge commercial potential of MTG, such as for applications in salted protein foods.

Transglutaminases: part I-origins, sources, and biotechnological characteristics

The transglutaminases form a large family of intracellular and extracellular enzymes that catalyze cross-links between protein molecules. Transglutaminases crosslinking properties are widely applied to various industrial processes, to improve the firmness, viscosity, elasticity, and water-holding capacity of products in the food and pharmaceutical industries. However, the extremely high costs of obtaining transglutaminases from animal sources have prompted scientists to search for new sources of these enzymes. Therefore, research has been focused on producing transglutaminases by microorganisms, which may present wider scope of use, based on enzyme-specific characteristics. In this review, we present an overview of the literature addressing the origins, types, reactions, and general characterizations of this important enzyme family. A second review will deal with transglutaminases applications in the area of food industry, medicine, pharmaceuticals and biomaterials, as well as applications in the textile and leather industries.

Bioreactor-Scale Strategies for the Production of Recombinant Protein in the Yeast Yarrowia lipolytica

Recombinant protein production represents a multibillion-dollar market. Therefore, it constitutes an important research field both in academia and industry. The use of yeast as a cell factory presents several advantages such as ease of genetic manipulation, growth at high cell density, and the possibility of post-translational modifications. Yarrowia lipolytica is considered as one of the most attractive hosts due to its ability to metabolize raw substrate, to express genes at a high level, and to secrete protein in large amounts. In recent years, several reviews have been dedicated to genetic tools developed for this purpose. Though the construction of efficient cell factories for recombinant protein synthesis is important, the development of an efficient process for recombinant protein production in a bioreactor constitutes an equally vital aspect. Indeed, a sports car cannot drive fast on a gravel road. The aim of this review is to provide a comprehensive snapshot of process tools to consider for recombinant protein production in bioreactor using Y. lipolytica as a cell factory, in order to facilitate the decision-making for future strain and process engineering.

Saturation effect and transmembrane conversion of Monascus pigment in nonionic surfactant aqueous solution

Extractive fermentation in a nonionic surfactant aqueous solution provides a promising and efficient method to produce Monascus pigments. The behaviour of pigment secretion during the extractive cultivation was investigated in the present work. The results revealed that the secretion of intracellular pigment was limited by its saturation concentration in the nonionic surfactant aqueous solution. The intracellular pigment was completely extracted to the outside of the cell at a low cell density and high concentration of Triton X-100 (TX) in fermentation broth; otherwise, a restriction for pigment extraction would occur. The decrement of the intracellular orange and yellow pigments was inconsistent with the increment of extracellular pigments with an increase in the TX concentration. It could be inferred that the intracellular orange pigment was converted to extracellular yellow pigment during the transmembrane secretion process, which might be attributed to the enzyme catalysis in the non-aqueous phase solution. This study helps explain the mechanism of variation of pigment characteristic and extraction capacity in extractive fermentation.

Development of nitrilase promoter-derived inducible vectors for Streptomyces

An inducible expression vector, pSH19, which harbors regulatory expression system PnitA-NitR, for streptomycetes was constructed previously. Here, we have modified pSH19 to obtain shuttle vectors for Streptomyces-E. coli by introducing the replication origin of a plasmid for E. coli (ColE1) and an antibiotic-resistant gene. Six inducible shuttle vectors, pESH19cF, pESH19cR, pESH19kF, pESH19kR, pESH19aF, and pESH19aR, for Streptomyces-E. coli, were successfully developed. The stability of these vectors was examined in five different E. coli strains and Streptomyces lividans TK24. The stability test showed that the pSH19-derived shuttle vectors were stable in E. coli Stbl2 and S. lividans TK24. Heterologous expression experiments involving each of the catechol 2,3-dioxygenase, nitrilase, and N-substituted formamide deformylase genes as a reporter gene showed that pESH19cF, pESH19kF, and pESH19aF possess inducible expression ability in S. lividans TK24. Thus, these vectors were found to be useful expression tools for experiments on both Gram-negative and Gram-positive bacterial genes.

A novel strain of Yarrowia lipolytica as a platform for value-added product synthesis from glycerol

BACKGROUND

Increasing interest of non-conventional yeasts has been observed for many years due to their biochemical characteristics and potential applications. Well-studied, oleaginous yeast Y. lipolytica is an attractive host for converting a low-cost glycerol, into value-added products such as erythritol (sweetener) or citric acid. Glycerol is an important renewable feedstock and is the main co-product of biodiesel production, which is nowadays applied on a large commercial scale. To this end, we engineered the yeast Y. lipolytica to increase the productivity of this strain.

RESULTS

In this light, we enhanced glycerol assimilation by over-expression of the YALI0F00484g gene encoding glycerol kinase (GK) and gene YALI0B02948g encoding glycerol-3-P dehydrogenase (GDH). The modified strains have been tested for glycerol consumption rate and erythritol and citric acid synthesis under various conditions. Here, we show that the overexpression of GK and GDH, increased glycerol consumption resulting in rapid erythritol and citric acid synthesis. Next, we combined the two genes in the tandem gene construct for the simultaneous co-expression of GK and GDH, which further increased the desired product synthesis. The glycerol consumption was explored in a 5-L bioreactor and the engineered strains were able to utilize 150 g/L glycerol within 44-48 hours. The erythritol productivity for GK overexpression and co-expression of GK and DGH was 24 and 35 %, respectively, over the control strain. Moreover, we established conditions for the production of citric acid at pH 3.0, the engineered strains increased citric acid production 14-fold over the control.

CONCLUSION

This work demonstrates the excellent capacity of the engineered strains as a starting platform for further modification for broad-range value-added product biosynthesis from glycerol. This study presents the highest reported titer citric acid at low pH to date. The process parameters such as productivity and yield of erythritol and citric acid were significantly elevated, what is valuable for industrial applications.